/*
   * udlfb.c -- Framebuffer driver for DisplayLink USB controller
   *
   * Copyright (C) 2009 Roberto De Ioris <roberto@unbit.it>
   * Copyright (C) 2009 Jaya Kumar <jayakumar.lkml@gmail.com>

   * Copyright (C) 2009 Bernie Thompson <bernie@plugable.com>

   *
   * This file is subject to the terms and conditions of the GNU General Public
   * License v2. See the file COPYING in the main directory of this archive for
   * more details.
   *
   * Layout is based on skeletonfb by James Simmons and Geert Uytterhoeven,
   * usb-skeleton by GregKH.
   *
   * Device-specific portions based on information from Displaylink, with work
   * from Florian Echtler, Henrik Bjerregaard Pedersen, and others.
   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/module.h>
  #include <linux/kernel.h>
  #include <linux/init.h>
  #include <linux/usb.h>
  #include <linux/uaccess.h>
  #include <linux/mm.h>
  #include <linux/fb.h>

  #include <linux/vmalloc.h>

  #include <linux/slab.h>

  #include <linux/prefetch.h>

  #include <linux/delay.h>

  #include <video/udlfb.h>

  #include "edid.h"

  static struct fb_fix_screeninfo dlfb_fix = {

  	.id =           "udlfb",

  	.type =         FB_TYPE_PACKED_PIXELS,
  	.visual =       FB_VISUAL_TRUECOLOR,
  	.xpanstep =     0,
  	.ypanstep =     0,
  	.ywrapstep =    0,
  	.accel =        FB_ACCEL_NONE,

  };

  static const u32 udlfb_info_flags = FBINFO_DEFAULT | FBINFO_READS_FAST |

  		FBINFO_VIRTFB |

  		FBINFO_HWACCEL_IMAGEBLIT | FBINFO_HWACCEL_FILLRECT |
  		FBINFO_HWACCEL_COPYAREA | FBINFO_MISC_ALWAYS_SETPAR;

  /*

   * There are many DisplayLink-based graphics products, all with unique PIDs.
   * So we match on DisplayLink's VID + Vendor-Defined Interface Class (0xff)
   * We also require a match on SubClass (0x00) and Protocol (0x00),
   * which is compatible with all known USB 2.0 era graphics chips and firmware,
   * but allows DisplayLink to increment those for any future incompatible chips

   */
  static struct usb_device_id id_table[] = {

  	{.idVendor = 0x17e9,
  	 .bInterfaceClass = 0xff,
  	 .bInterfaceSubClass = 0x00,
  	 .bInterfaceProtocol = 0x00,
  	 .match_flags = USB_DEVICE_ID_MATCH_VENDOR |
  		USB_DEVICE_ID_MATCH_INT_CLASS |
  		USB_DEVICE_ID_MATCH_INT_SUBCLASS |
  		USB_DEVICE_ID_MATCH_INT_PROTOCOL,
  	},

  	{},
  };
  MODULE_DEVICE_TABLE(usb, id_table);

  /* module options */

  static bool console = 1; /* Allow fbcon to open framebuffer */
  static bool fb_defio = 1;  /* Detect mmap writes using page faults */
  static bool shadow = 1; /* Optionally disable shadow framebuffer */

  /* dlfb keeps a list of urbs for efficient bulk transfers */
  static void dlfb_urb_completion(struct urb *urb);
  static struct urb *dlfb_get_urb(struct dlfb_data *dev);
  static int dlfb_submit_urb(struct dlfb_data *dev, struct urb * urb, size_t len);
  static int dlfb_alloc_urb_list(struct dlfb_data *dev, int count, size_t size);
  static void dlfb_free_urb_list(struct dlfb_data *dev);

  /*

   * All DisplayLink bulk operations start with 0xAF, followed by specific code
   * All operations are written to buffers which then later get sent to device

   */

  static char *dlfb_set_register(char *buf, u8 reg, u8 val)

  {

  	*buf++ = 0xAF;
  	*buf++ = 0x20;
  	*buf++ = reg;
  	*buf++ = val;
  	return buf;

  }

  static char *dlfb_vidreg_lock(char *buf)

  {

  	return dlfb_set_register(buf, 0xFF, 0x00);

  }

  static char *dlfb_vidreg_unlock(char *buf)

  {

  	return dlfb_set_register(buf, 0xFF, 0xFF);

  }
  
  /*

   * Map FB_BLANK_* to DisplayLink register
   * DLReg FB_BLANK_*
   * ----- -----------------------------
   *  0x00 FB_BLANK_UNBLANK (0)
   *  0x01 FB_BLANK (1)
   *  0x03 FB_BLANK_VSYNC_SUSPEND (2)
   *  0x05 FB_BLANK_HSYNC_SUSPEND (3)
   *  0x07 FB_BLANK_POWERDOWN (4) Note: requires modeset to come back

   */

  static char *dlfb_blanking(char *buf, int fb_blank)

  {

  	u8 reg;
  
  	switch (fb_blank) {
  	case FB_BLANK_POWERDOWN:
  		reg = 0x07;
  		break;
  	case FB_BLANK_HSYNC_SUSPEND:
  		reg = 0x05;
  		break;
  	case FB_BLANK_VSYNC_SUSPEND:
  		reg = 0x03;
  		break;
  	case FB_BLANK_NORMAL:
  		reg = 0x01;
  		break;
  	default:
  		reg = 0x00;
  	}
  
  	buf = dlfb_set_register(buf, 0x1F, reg);
  
  	return buf;

  }

  static char *dlfb_set_color_depth(char *buf, u8 selection)

  {

  	return dlfb_set_register(buf, 0x00, selection);

  }

  static char *dlfb_set_base16bpp(char *wrptr, u32 base)

  {

  	/* the base pointer is 16 bits wide, 0x20 is hi byte. */

  	wrptr = dlfb_set_register(wrptr, 0x20, base >> 16);
  	wrptr = dlfb_set_register(wrptr, 0x21, base >> 8);
  	return dlfb_set_register(wrptr, 0x22, base);

  }

  /*
   * DisplayLink HW has separate 16bpp and 8bpp framebuffers.
   * In 24bpp modes, the low 323 RGB bits go in the 8bpp framebuffer
   */

  static char *dlfb_set_base8bpp(char *wrptr, u32 base)

  {

  	wrptr = dlfb_set_register(wrptr, 0x26, base >> 16);
  	wrptr = dlfb_set_register(wrptr, 0x27, base >> 8);
  	return dlfb_set_register(wrptr, 0x28, base);

  }

  static char *dlfb_set_register_16(char *wrptr, u8 reg, u16 value)

  {

  	wrptr = dlfb_set_register(wrptr, reg, value >> 8);
  	return dlfb_set_register(wrptr, reg+1, value);

  }
  
  /*
   * This is kind of weird because the controller takes some
   * register values in a different byte order than other registers.
   */

  static char *dlfb_set_register_16be(char *wrptr, u8 reg, u16 value)

  {

  	wrptr = dlfb_set_register(wrptr, reg, value);
  	return dlfb_set_register(wrptr, reg+1, value >> 8);

  }
  
  /*
   * LFSR is linear feedback shift register. The reason we have this is
   * because the display controller needs to minimize the clock depth of
   * various counters used in the display path. So this code reverses the
   * provided value into the lfsr16 value by counting backwards to get
   * the value that needs to be set in the hardware comparator to get the
   * same actual count. This makes sense once you read above a couple of
   * times and think about it from a hardware perspective.
   */

  static u16 dlfb_lfsr16(u16 actual_count)

  {
  	u32 lv = 0xFFFF; /* This is the lfsr value that the hw starts with */
  
  	while (actual_count--) {
  		lv =	 ((lv << 1) |
  			(((lv >> 15) ^ (lv >> 4) ^ (lv >> 2) ^ (lv >> 1)) & 1))
  			& 0xFFFF;

  	}

  	return (u16) lv;
  }
  
  /*
   * This does LFSR conversion on the value that is to be written.
   * See LFSR explanation above for more detail.
   */

  static char *dlfb_set_register_lfsr16(char *wrptr, u8 reg, u16 value)

  {

  	return dlfb_set_register_16(wrptr, reg, dlfb_lfsr16(value));

  }

  /*
   * This takes a standard fbdev screeninfo struct and all of its monitor mode
   * details and converts them into the DisplayLink equivalent register commands.
   */

  static char *dlfb_set_vid_cmds(char *wrptr, struct fb_var_screeninfo *var)

  {

  	u16 xds, yds;
  	u16 xde, yde;
  	u16 yec;

  	/* x display start */
  	xds = var->left_margin + var->hsync_len;

  	wrptr = dlfb_set_register_lfsr16(wrptr, 0x01, xds);

  	/* x display end */
  	xde = xds + var->xres;

  	wrptr = dlfb_set_register_lfsr16(wrptr, 0x03, xde);

  
  	/* y display start */
  	yds = var->upper_margin + var->vsync_len;

  	wrptr = dlfb_set_register_lfsr16(wrptr, 0x05, yds);

  	/* y display end */
  	yde = yds + var->yres;

  	wrptr = dlfb_set_register_lfsr16(wrptr, 0x07, yde);

  
  	/* x end count is active + blanking - 1 */

  	wrptr = dlfb_set_register_lfsr16(wrptr, 0x09,
  			xde + var->right_margin - 1);

  
  	/* libdlo hardcodes hsync start to 1 */

  	wrptr = dlfb_set_register_lfsr16(wrptr, 0x0B, 1);

  
  	/* hsync end is width of sync pulse + 1 */

  	wrptr = dlfb_set_register_lfsr16(wrptr, 0x0D, var->hsync_len + 1);

  
  	/* hpixels is active pixels */

  	wrptr = dlfb_set_register_16(wrptr, 0x0F, var->xres);

  	/* yendcount is vertical active + vertical blanking */
  	yec = var->yres + var->upper_margin + var->lower_margin +
  			var->vsync_len;

  	wrptr = dlfb_set_register_lfsr16(wrptr, 0x11, yec);

  	/* libdlo hardcodes vsync start to 0 */

  	wrptr = dlfb_set_register_lfsr16(wrptr, 0x13, 0);

  
  	/* vsync end is width of vsync pulse */

  	wrptr = dlfb_set_register_lfsr16(wrptr, 0x15, var->vsync_len);

  
  	/* vpixels is active pixels */

  	wrptr = dlfb_set_register_16(wrptr, 0x17, var->yres);

  
  	/* convert picoseconds to 5kHz multiple for pclk5k = x * 1E12/5k */

  	wrptr = dlfb_set_register_16be(wrptr, 0x1B,
  			200*1000*1000/var->pixclock);

  
  	return wrptr;
  }
  
  /*
   * This takes a standard fbdev screeninfo struct that was fetched or prepared
   * and then generates the appropriate command sequence that then drives the
   * display controller.
   */
  static int dlfb_set_video_mode(struct dlfb_data *dev,
  				struct fb_var_screeninfo *var)
  {
  	char *buf;
  	char *wrptr;
  	int retval = 0;
  	int writesize;

  	struct urb *urb;
  
  	if (!atomic_read(&dev->usb_active))
  		return -EPERM;

  	urb = dlfb_get_urb(dev);
  	if (!urb)
  		return -ENOMEM;

  	buf = (char *) urb->transfer_buffer;

  
  	/*
  	* This first section has to do with setting the base address on the
  	* controller * associated with the display. There are 2 base
  	* pointers, currently, we only * use the 16 bpp segment.
  	*/

  	wrptr = dlfb_vidreg_lock(buf);
  	wrptr = dlfb_set_color_depth(wrptr, 0x00);

  	/* set base for 16bpp segment to 0 */

  	wrptr = dlfb_set_base16bpp(wrptr, 0);

  	/* set base for 8bpp segment to end of fb */

  	wrptr = dlfb_set_base8bpp(wrptr, dev->info->fix.smem_len);

  	wrptr = dlfb_set_vid_cmds(wrptr, var);

  	wrptr = dlfb_blanking(wrptr, FB_BLANK_UNBLANK);

  	wrptr = dlfb_vidreg_unlock(wrptr);

  
  	writesize = wrptr - buf;

  	retval = dlfb_submit_urb(dev, urb, writesize);

  	dev->blank_mode = FB_BLANK_UNBLANK;

  	return retval;
  }

  static int dlfb_ops_mmap(struct fb_info *info, struct vm_area_struct *vma)

  {
  	unsigned long start = vma->vm_start;
  	unsigned long size = vma->vm_end - vma->vm_start;
  	unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
  	unsigned long page, pos;

  	if (offset + size > info->fix.smem_len)

  		return -EINVAL;

  
  	pos = (unsigned long)info->fix.smem_start + offset;

  	pr_notice("mmap() framebuffer addr:%lu size:%lu
  ",

  		  pos, size);

  	while (size > 0) {
  		page = vmalloc_to_pfn((void *)pos);

  		if (remap_pfn_range(vma, start, page, PAGE_SIZE, PAGE_SHARED))

  			return -EAGAIN;

  		start += PAGE_SIZE;
  		pos += PAGE_SIZE;
  		if (size > PAGE_SIZE)
  			size -= PAGE_SIZE;
  		else
  			size = 0;
  	}
  
  	vma->vm_flags |= VM_RESERVED;	/* avoid to swap out this VMA */
  	return 0;

  }

  /*
   * Trims identical data from front and back of line
   * Sets new front buffer address and width
   * And returns byte count of identical pixels
   * Assumes CPU natural alignment (unsigned long)
   * for back and front buffer ptrs and width
   */
  static int dlfb_trim_hline(const u8 *bback, const u8 **bfront, int *width_bytes)

  {

  	int j, k;
  	const unsigned long *back = (const unsigned long *) bback;
  	const unsigned long *front = (const unsigned long *) *bfront;
  	const int width = *width_bytes / sizeof(unsigned long);
  	int identical = width;
  	int start = width;
  	int end = width;
  
  	prefetch((void *) front);
  	prefetch((void *) back);
  
  	for (j = 0; j < width; j++) {
  		if (back[j] != front[j]) {
  			start = j;
  			break;
  		}
  	}

  	for (k = width - 1; k > j; k--) {
  		if (back[k] != front[k]) {
  			end = k+1;
  			break;
  		}

  	}

  	identical = start + (width - end);
  	*bfront = (u8 *) &front[start];
  	*width_bytes = (end - start) * sizeof(unsigned long);
  
  	return identical * sizeof(unsigned long);

  }
  
  /*

   * Render a command stream for an encoded horizontal line segment of pixels.
   *
   * A command buffer holds several commands.
   * It always begins with a fresh command header
   * (the protocol doesn't require this, but we enforce it to allow
   * multiple buffers to be potentially encoded and sent in parallel).
   * A single command encodes one contiguous horizontal line of pixels
   *
   * The function relies on the client to do all allocation, so that
   * rendering can be done directly to output buffers (e.g. USB URBs).
   * The function fills the supplied command buffer, providing information
   * on where it left off, so the client may call in again with additional
   * buffers if the line will take several buffers to complete.
   *
   * A single command can transmit a maximum of 256 pixels,
   * regardless of the compression ratio (protocol design limit).
   * To the hardware, 0 for a size byte means 256

   *

   * Rather than 256 pixel commands which are either rl or raw encoded,
   * the rlx command simply assumes alternating raw and rl spans within one cmd.
   * This has a slightly larger header overhead, but produces more even results.
   * It also processes all data (read and write) in a single pass.
   * Performance benchmarks of common cases show it having just slightly better

   * compression than 256 pixel raw or rle commands, with similar CPU consumpion.

   * But for very rl friendly data, will compress not quite as well.
   */

  static void dlfb_compress_hline(
  	const uint16_t **pixel_start_ptr,
  	const uint16_t *const pixel_end,
  	uint32_t *device_address_ptr,
  	uint8_t **command_buffer_ptr,
  	const uint8_t *const cmd_buffer_end)

  {

  	const uint16_t *pixel = *pixel_start_ptr;
  	uint32_t dev_addr  = *device_address_ptr;
  	uint8_t *cmd = *command_buffer_ptr;
  	const int bpp = 2;
  
  	while ((pixel_end > pixel) &&
  	       (cmd_buffer_end - MIN_RLX_CMD_BYTES > cmd)) {
  		uint8_t *raw_pixels_count_byte = 0;
  		uint8_t *cmd_pixels_count_byte = 0;
  		const uint16_t *raw_pixel_start = 0;
  		const uint16_t *cmd_pixel_start, *cmd_pixel_end = 0;

  
  		prefetchw((void *) cmd); /* pull in one cache line at least */
  
  		*cmd++ = 0xAF;
  		*cmd++ = 0x6B;

  		*cmd++ = (uint8_t) ((dev_addr >> 16) & 0xFF);
  		*cmd++ = (uint8_t) ((dev_addr >> 8) & 0xFF);
  		*cmd++ = (uint8_t) ((dev_addr) & 0xFF);

  
  		cmd_pixels_count_byte = cmd++; /*  we'll know this later */
  		cmd_pixel_start = pixel;
  
  		raw_pixels_count_byte = cmd++; /*  we'll know this later */
  		raw_pixel_start = pixel;
  
  		cmd_pixel_end = pixel + min(MAX_CMD_PIXELS + 1,
  			min((int)(pixel_end - pixel),
  			    (int)(cmd_buffer_end - cmd) / bpp));
  
  		prefetch_range((void *) pixel, (cmd_pixel_end - pixel) * bpp);
  
  		while (pixel < cmd_pixel_end) {
  			const uint16_t * const repeating_pixel = pixel;
  
  			*(uint16_t *)cmd = cpu_to_be16p(pixel);
  			cmd += 2;
  			pixel++;
  
  			if (unlikely((pixel < cmd_pixel_end) &&
  				     (*pixel == *repeating_pixel))) {
  				/* go back and fill in raw pixel count */
  				*raw_pixels_count_byte = ((repeating_pixel -
  						raw_pixel_start) + 1) & 0xFF;
  
  				while ((pixel < cmd_pixel_end)
  				       && (*pixel == *repeating_pixel)) {
  					pixel++;

  				}

  				/* immediately after raw data is repeat byte */
  				*cmd++ = ((pixel - repeating_pixel) - 1) & 0xFF;

  				/* Then start another raw pixel span */
  				raw_pixel_start = pixel;
  				raw_pixels_count_byte = cmd++;

  			}

  		}

  		if (pixel > raw_pixel_start) {
  			/* finalize last RAW span */
  			*raw_pixels_count_byte = (pixel-raw_pixel_start) & 0xFF;
  		}

  		*cmd_pixels_count_byte = (pixel - cmd_pixel_start) & 0xFF;
  		dev_addr += (pixel - cmd_pixel_start) * bpp;

  	}

  	if (cmd_buffer_end <= MIN_RLX_CMD_BYTES + cmd) {
  		/* Fill leftover bytes with no-ops */
  		if (cmd_buffer_end > cmd)
  			memset(cmd, 0xAF, cmd_buffer_end - cmd);
  		cmd = (uint8_t *) cmd_buffer_end;

  	}

  	*command_buffer_ptr = cmd;
  	*pixel_start_ptr = pixel;
  	*device_address_ptr = dev_addr;

  	return;

  }

  /*
   * There are 3 copies of every pixel: The front buffer that the fbdev
   * client renders to, the actual framebuffer across the USB bus in hardware
   * (that we can only write to, slowly, and can never read), and (optionally)
   * our shadow copy that tracks what's been sent to that hardware buffer.
   */

  static int dlfb_render_hline(struct dlfb_data *dev, struct urb **urb_ptr,

  			      const char *front, char **urb_buf_ptr,
  			      u32 byte_offset, u32 byte_width,
  			      int *ident_ptr, int *sent_ptr)

  {

  	const u8 *line_start, *line_end, *next_pixel;
  	u32 dev_addr = dev->base16 + byte_offset;
  	struct urb *urb = *urb_ptr;
  	u8 *cmd = *urb_buf_ptr;
  	u8 *cmd_end = (u8 *) urb->transfer_buffer + urb->transfer_buffer_length;
  
  	line_start = (u8 *) (front + byte_offset);
  	next_pixel = line_start;
  	line_end = next_pixel + byte_width;
  
  	if (dev->backing_buffer) {
  		int offset;
  		const u8 *back_start = (u8 *) (dev->backing_buffer
  						+ byte_offset);
  
  		*ident_ptr += dlfb_trim_hline(back_start, &next_pixel,
  			&byte_width);
  
  		offset = next_pixel - line_start;
  		line_end = next_pixel + byte_width;
  		dev_addr += offset;
  		back_start += offset;
  		line_start += offset;
  
  		memcpy((char *)back_start, (char *) line_start,
  		       byte_width);
  	}

  	while (next_pixel < line_end) {
  
  		dlfb_compress_hline((const uint16_t **) &next_pixel,
  			     (const uint16_t *) line_end, &dev_addr,
  			(u8 **) &cmd, (u8 *) cmd_end);
  
  		if (cmd >= cmd_end) {
  			int len = cmd - (u8 *) urb->transfer_buffer;
  			if (dlfb_submit_urb(dev, urb, len))

  				return 1; /* lost pixels is set */

  			*sent_ptr += len;
  			urb = dlfb_get_urb(dev);
  			if (!urb)

  				return 1; /* lost_pixels is set */

  			*urb_ptr = urb;
  			cmd = urb->transfer_buffer;
  			cmd_end = &cmd[urb->transfer_buffer_length];

  		}

  	}

  	*urb_buf_ptr = cmd;

  
  	return 0;

  }

  int dlfb_handle_damage(struct dlfb_data *dev, int x, int y,
  	       int width, int height, char *data)

  {

  	int i, ret;

  	char *cmd;
  	cycles_t start_cycles, end_cycles;
  	int bytes_sent = 0;
  	int bytes_identical = 0;
  	struct urb *urb;
  	int aligned_x;
  
  	start_cycles = get_cycles();
  
  	aligned_x = DL_ALIGN_DOWN(x, sizeof(unsigned long));
  	width = DL_ALIGN_UP(width + (x-aligned_x), sizeof(unsigned long));
  	x = aligned_x;
  
  	if ((width <= 0) ||
  	    (x + width > dev->info->var.xres) ||
  	    (y + height > dev->info->var.yres))
  		return -EINVAL;

  	if (!atomic_read(&dev->usb_active))
  		return 0;

  	urb = dlfb_get_urb(dev);
  	if (!urb)
  		return 0;
  	cmd = urb->transfer_buffer;

  	for (i = y; i < y + height ; i++) {
  		const int line_offset = dev->info->fix.line_length * i;
  		const int byte_offset = line_offset + (x * BPP);

  		if (dlfb_render_hline(dev, &urb,
  				      (char *) dev->info->fix.smem_start,

  				      &cmd, byte_offset, width * BPP,

  				      &bytes_identical, &bytes_sent))
  			goto error;

  	}

  	if (cmd > (char *) urb->transfer_buffer) {
  		/* Send partial buffer remaining before exiting */
  		int len = cmd - (char *) urb->transfer_buffer;
  		ret = dlfb_submit_urb(dev, urb, len);
  		bytes_sent += len;
  	} else
  		dlfb_urb_completion(urb);

  error:

  	atomic_add(bytes_sent, &dev->bytes_sent);
  	atomic_add(bytes_identical, &dev->bytes_identical);
  	atomic_add(width*height*2, &dev->bytes_rendered);
  	end_cycles = get_cycles();
  	atomic_add(((unsigned int) ((end_cycles - start_cycles)
  		    >> 10)), /* Kcycles */
  		   &dev->cpu_kcycles_used);

  	return 0;

  }

  /*
   * Path triggered by usermode clients who write to filesystem
   * e.g. cat filename > /dev/fb1
   * Not used by X Windows or text-mode console. But useful for testing.
   * Slow because of extra copy and we must assume all pixels dirty.
   */
  static ssize_t dlfb_ops_write(struct fb_info *info, const char __user *buf,
  			  size_t count, loff_t *ppos)
  {

  	ssize_t result;

  	struct dlfb_data *dev = info->par;
  	u32 offset = (u32) *ppos;

  	result = fb_sys_write(info, buf, count, ppos);
  
  	if (result > 0) {
  		int start = max((int)(offset / info->fix.line_length) - 1, 0);
  		int lines = min((u32)((result / info->fix.line_length) + 1),
  				(u32)info->var.yres);
  
  		dlfb_handle_damage(dev, 0, start, info->var.xres,
  			lines, info->screen_base);
  	}

  
  	return result;
  }

  /* hardware has native COPY command (see libdlo), but not worth it for fbcon */
  static void dlfb_ops_copyarea(struct fb_info *info,
  				const struct fb_copyarea *area)

  {

  	struct dlfb_data *dev = info->par;

  	sys_copyarea(info, area);

  	dlfb_handle_damage(dev, area->dx, area->dy,
  			area->width, area->height, info->screen_base);

  }

  static void dlfb_ops_imageblit(struct fb_info *info,
  				const struct fb_image *image)
  {
  	struct dlfb_data *dev = info->par;

  	sys_imageblit(info, image);

  	dlfb_handle_damage(dev, image->dx, image->dy,
  			image->width, image->height, info->screen_base);

  }

  static void dlfb_ops_fillrect(struct fb_info *info,
  			  const struct fb_fillrect *rect)

  {

  	struct dlfb_data *dev = info->par;

  	sys_fillrect(info, rect);

  	dlfb_handle_damage(dev, rect->dx, rect->dy, rect->width,
  			      rect->height, info->screen_base);

  }

  /*
   * NOTE: fb_defio.c is holding info->fbdefio.mutex
   *   Touching ANY framebuffer memory that triggers a page fault
   *   in fb_defio will cause a deadlock, when it also tries to
   *   grab the same mutex.
   */
  static void dlfb_dpy_deferred_io(struct fb_info *info,
  				struct list_head *pagelist)
  {
  	struct page *cur;
  	struct fb_deferred_io *fbdefio = info->fbdefio;
  	struct dlfb_data *dev = info->par;
  	struct urb *urb;
  	char *cmd;
  	cycles_t start_cycles, end_cycles;
  	int bytes_sent = 0;
  	int bytes_identical = 0;
  	int bytes_rendered = 0;
  
  	if (!fb_defio)
  		return;
  
  	if (!atomic_read(&dev->usb_active))
  		return;
  
  	start_cycles = get_cycles();
  
  	urb = dlfb_get_urb(dev);
  	if (!urb)
  		return;
  
  	cmd = urb->transfer_buffer;
  
  	/* walk the written page list and render each to device */
  	list_for_each_entry(cur, &fbdefio->pagelist, lru) {

  		if (dlfb_render_hline(dev, &urb, (char *) info->fix.smem_start,

  				  &cmd, cur->index << PAGE_SHIFT,

  				  PAGE_SIZE, &bytes_identical, &bytes_sent))
  			goto error;

  		bytes_rendered += PAGE_SIZE;
  	}
  
  	if (cmd > (char *) urb->transfer_buffer) {
  		/* Send partial buffer remaining before exiting */
  		int len = cmd - (char *) urb->transfer_buffer;
  		dlfb_submit_urb(dev, urb, len);
  		bytes_sent += len;
  	} else
  		dlfb_urb_completion(urb);

  error:

  	atomic_add(bytes_sent, &dev->bytes_sent);
  	atomic_add(bytes_identical, &dev->bytes_identical);
  	atomic_add(bytes_rendered, &dev->bytes_rendered);
  	end_cycles = get_cycles();
  	atomic_add(((unsigned int) ((end_cycles - start_cycles)
  		    >> 10)), /* Kcycles */
  		   &dev->cpu_kcycles_used);
  }

  static int dlfb_get_edid(struct dlfb_data *dev, char *edid, int len)

  {
  	int i;
  	int ret;

  	char *rbuf;

  	rbuf = kmalloc(2, GFP_KERNEL);
  	if (!rbuf)
  		return 0;
  
  	for (i = 0; i < len; i++) {

  		ret = usb_control_msg(dev->udev,
  				    usb_rcvctrlpipe(dev->udev, 0), (0x02),
  				    (0x80 | (0x02 << 5)), i << 8, 0xA1, rbuf, 2,

  				    HZ);
  		if (ret < 1) {

  			pr_err("Read EDID byte %d failed err %x
  ", i, ret);

  			i--;
  			break;
  		}
  		edid[i] = rbuf[1];

  	}

  
  	kfree(rbuf);
  
  	return i;

  }

  static int dlfb_ops_ioctl(struct fb_info *info, unsigned int cmd,

  				unsigned long arg)

  {

  
  	struct dlfb_data *dev = info->par;

  	if (!atomic_read(&dev->usb_active))
  		return 0;
  
  	/* TODO: Update X server to get this from sysfs instead */
  	if (cmd == DLFB_IOCTL_RETURN_EDID) {

  		void __user *edid = (void __user *)arg;

  		if (copy_to_user(edid, dev->edid, dev->edid_size))

  			return -EFAULT;

  		return 0;
  	}

  	/* TODO: Help propose a standard fb.h ioctl to report mmap damage */
  	if (cmd == DLFB_IOCTL_REPORT_DAMAGE) {

  		struct dloarea area;
  
  		if (copy_from_user(&area, (void __user *)arg,
  				  sizeof(struct dloarea)))
  			return -EFAULT;

  		/*
  		 * If we have a damage-aware client, turn fb_defio "off"

  		 * To avoid perf imact of unnecessary page fault handling.

  		 * Done by resetting the delay for this fb_info to a very
  		 * long period. Pages will become writable and stay that way.
  		 * Reset to normal value when all clients have closed this fb.
  		 */
  		if (info->fbdefio)
  			info->fbdefio->delay = DL_DEFIO_WRITE_DISABLE;

  		if (area.x < 0)
  			area.x = 0;

  		if (area.x > info->var.xres)
  			area.x = info->var.xres;

  		if (area.y < 0)
  			area.y = 0;

  		if (area.y > info->var.yres)
  			area.y = info->var.yres;

  		dlfb_handle_damage(dev, area.x, area.y, area.w, area.h,

  			   info->screen_base);
  	}

  	return 0;
  }

  /* taken from vesafb */

  static int

  dlfb_ops_setcolreg(unsigned regno, unsigned red, unsigned green,

  	       unsigned blue, unsigned transp, struct fb_info *info)
  {
  	int err = 0;
  
  	if (regno >= info->cmap.len)
  		return 1;
  
  	if (regno < 16) {
  		if (info->var.red.offset == 10) {
  			/* 1:5:5:5 */
  			((u32 *) (info->pseudo_palette))[regno] =
  			    ((red & 0xf800) >> 1) |
  			    ((green & 0xf800) >> 6) | ((blue & 0xf800) >> 11);
  		} else {
  			/* 0:5:6:5 */
  			((u32 *) (info->pseudo_palette))[regno] =
  			    ((red & 0xf800)) |
  			    ((green & 0xfc00) >> 5) | ((blue & 0xf800) >> 11);
  		}
  	}
  
  	return err;
  }

  /*
   * It's common for several clients to have framebuffer open simultaneously.
   * e.g. both fbcon and X. Makes things interesting.

   * Assumes caller is holding info->lock (for open and release at least)

   */
  static int dlfb_ops_open(struct fb_info *info, int user)
  {
  	struct dlfb_data *dev = info->par;

  	/*
  	 * fbcon aggressively connects to first framebuffer it finds,
  	 * preventing other clients (X) from working properly. Usually
  	 * not what the user wants. Fail by default with option to enable.
  	 */

  	if ((user == 0) && (!console))

  		return -EBUSY;

  	/* If the USB device is gone, we don't accept new opens */
  	if (dev->virtualized)
  		return -ENODEV;

  
  	dev->fb_count++;

  	kref_get(&dev->kref);

  	if (fb_defio && (info->fbdefio == NULL)) {

  		/* enable defio at last moment if not disabled by client */
  
  		struct fb_deferred_io *fbdefio;

  		fbdefio = kmalloc(sizeof(struct fb_deferred_io), GFP_KERNEL);

  
  		if (fbdefio) {
  			fbdefio->delay = DL_DEFIO_WRITE_DELAY;
  			fbdefio->deferred_io = dlfb_dpy_deferred_io;
  		}
  
  		info->fbdefio = fbdefio;

  		fb_deferred_io_init(info);
  	}

  	pr_notice("open /dev/fb%d user=%d fb_info=%p count=%d
  ",

  	    info->node, user, info, dev->fb_count);

  	return 0;
  }

  /*
   * Called when all client interfaces to start transactions have been disabled,
   * and all references to our device instance (dlfb_data) are released.
   * Every transaction must have a reference, so we know are fully spun down
   */

  static void dlfb_free(struct kref *kref)

  {
  	struct dlfb_data *dev = container_of(kref, struct dlfb_data, kref);

  	/* this function will wait for all in-flight urbs to complete */
  	if (dev->urbs.count > 0)
  		dlfb_free_urb_list(dev);

  	if (dev->backing_buffer)
  		vfree(dev->backing_buffer);

  	kfree(dev->edid);

  	pr_warn("freeing dlfb_data %p
  ", dev);

  	kfree(dev);
  }

  static void dlfb_release_urb_work(struct work_struct *work)
  {
  	struct urb_node *unode = container_of(work, struct urb_node,
  					      release_urb_work.work);
  
  	up(&unode->dev->urbs.limit_sem);
  }

  
  static void dlfb_free_framebuffer_work(struct work_struct *work)

  {

  	struct dlfb_data *dev = container_of(work, struct dlfb_data,
  					     free_framebuffer_work.work);
  	struct fb_info *info = dev->info;
  	int node = info->node;
  
  	unregister_framebuffer(info);

  
  	if (info->cmap.len != 0)
  		fb_dealloc_cmap(&info->cmap);
  	if (info->monspecs.modedb)
  		fb_destroy_modedb(info->monspecs.modedb);
  	if (info->screen_base)
  		vfree(info->screen_base);
  
  	fb_destroy_modelist(&info->modelist);

  	dev->info = 0;
  
  	/* Assume info structure is freed after this point */

  	framebuffer_release(info);

  	pr_warn("fb_info for /dev/fb%d has been freed
  ", node);

  
  	/* ref taken in probe() as part of registering framebfufer */
  	kref_put(&dev->kref, dlfb_free);
  }
  
  /*
   * Assumes caller is holding info->lock mutex (for open and release at least)
   */
  static int dlfb_ops_release(struct fb_info *info, int user)
  {
  	struct dlfb_data *dev = info->par;
  
  	dev->fb_count--;
  
  	/* We can't free fb_info here - fbmem will touch it when we return */
  	if (dev->virtualized && (dev->fb_count == 0))
  		schedule_delayed_work(&dev->free_framebuffer_work, HZ);

  	if ((dev->fb_count == 0) && (info->fbdefio)) {
  		fb_deferred_io_cleanup(info);
  		kfree(info->fbdefio);
  		info->fbdefio = NULL;
  		info->fbops->fb_mmap = dlfb_ops_mmap;
  	}

  	pr_warn("released /dev/fb%d user=%d count=%d
  ",

  		  info->node, user, dev->fb_count);
  
  	kref_put(&dev->kref, dlfb_free);
  
  	return 0;

  }
  
  /*

   * Check whether a video mode is supported by the DisplayLink chip
   * We start from monitor's modes, so don't need to filter that here
   */
  static int dlfb_is_valid_mode(struct fb_videomode *mode,
  		struct fb_info *info)
  {
  	struct dlfb_data *dev = info->par;

  	if (mode->xres * mode->yres > dev->sku_pixel_limit) {

  		pr_warn("%dx%d beyond chip capabilities
  ",

  		       mode->xres, mode->yres);

  		return 0;

  	}

  	pr_info("%dx%d valid mode
  ", mode->xres, mode->yres);

  
  	return 1;
  }
  
  static void dlfb_var_color_format(struct fb_var_screeninfo *var)
  {
  	const struct fb_bitfield red = { 11, 5, 0 };
  	const struct fb_bitfield green = { 5, 6, 0 };
  	const struct fb_bitfield blue = { 0, 5, 0 };
  
  	var->bits_per_pixel = 16;
  	var->red = red;
  	var->green = green;
  	var->blue = blue;
  }

  static int dlfb_ops_check_var(struct fb_var_screeninfo *var,
  				struct fb_info *info)
  {
  	struct fb_videomode mode;
  
  	/* TODO: support dynamically changing framebuffer size */
  	if ((var->xres * var->yres * 2) > info->fix.smem_len)
  		return -EINVAL;
  
  	/* set device-specific elements of var unrelated to mode */
  	dlfb_var_color_format(var);
  
  	fb_var_to_videomode(&mode, var);
  
  	if (!dlfb_is_valid_mode(&mode, info))
  		return -EINVAL;
  
  	return 0;
  }
  
  static int dlfb_ops_set_par(struct fb_info *info)
  {
  	struct dlfb_data *dev = info->par;

  	int result;
  	u16 *pix_framebuffer;
  	int i;

  	pr_notice("set_par mode %dx%d
  ", info->var.xres, info->var.yres);

  	result = dlfb_set_video_mode(dev, &info->var);
  
  	if ((result == 0) && (dev->fb_count == 0)) {
  
  		/* paint greenscreen */
  
  		pix_framebuffer = (u16 *) info->screen_base;
  		for (i = 0; i < info->fix.smem_len / 2; i++)
  			pix_framebuffer[i] = 0x37e6;
  
  		dlfb_handle_damage(dev, 0, 0, info->var.xres, info->var.yres,
  				   info->screen_base);
  	}
  
  	return result;

  }

  /* To fonzi the jukebox (e.g. make blanking changes take effect) */
  static char *dlfb_dummy_render(char *buf)
  {
  	*buf++ = 0xAF;
  	*buf++ = 0x6A; /* copy */
  	*buf++ = 0x00; /* from address*/
  	*buf++ = 0x00;
  	*buf++ = 0x00;
  	*buf++ = 0x01; /* one pixel */
  	*buf++ = 0x00; /* to address */
  	*buf++ = 0x00;
  	*buf++ = 0x00;
  	return buf;
  }

  /*
   * In order to come back from full DPMS off, we need to set the mode again
   */

  static int dlfb_ops_blank(int blank_mode, struct fb_info *info)

  {

  	struct dlfb_data *dev = info->par;

  	char *bufptr;
  	struct urb *urb;

  	pr_info("/dev/fb%d FB_BLANK mode %d --> %d
  ",
  		info->node, dev->blank_mode, blank_mode);

  	if ((dev->blank_mode == FB_BLANK_POWERDOWN) &&
  	    (blank_mode != FB_BLANK_POWERDOWN)) {

  		/* returning from powerdown requires a fresh modeset */

  		dlfb_set_video_mode(dev, &info->var);

  	}

  	urb = dlfb_get_urb(dev);
  	if (!urb)
  		return 0;
  
  	bufptr = (char *) urb->transfer_buffer;
  	bufptr = dlfb_vidreg_lock(bufptr);
  	bufptr = dlfb_blanking(bufptr, blank_mode);
  	bufptr = dlfb_vidreg_unlock(bufptr);
  
  	/* seems like a render op is needed to have blank change take effect */
  	bufptr = dlfb_dummy_render(bufptr);
  
  	dlfb_submit_urb(dev, urb, bufptr -
  			(char *) urb->transfer_buffer);
  
  	dev->blank_mode = blank_mode;

  	return 0;
  }
  
  static struct fb_ops dlfb_ops = {

  	.owner = THIS_MODULE,

  	.fb_read = fb_sys_read,

  	.fb_write = dlfb_ops_write,

  	.fb_setcolreg = dlfb_ops_setcolreg,
  	.fb_fillrect = dlfb_ops_fillrect,
  	.fb_copyarea = dlfb_ops_copyarea,
  	.fb_imageblit = dlfb_ops_imageblit,
  	.fb_mmap = dlfb_ops_mmap,
  	.fb_ioctl = dlfb_ops_ioctl,

  	.fb_open = dlfb_ops_open,

  	.fb_release = dlfb_ops_release,
  	.fb_blank = dlfb_ops_blank,

  	.fb_check_var = dlfb_ops_check_var,
  	.fb_set_par = dlfb_ops_set_par,

  };

  /*

   * Assumes &info->lock held by caller
   * Assumes no active clients have framebuffer open
   */
  static int dlfb_realloc_framebuffer(struct dlfb_data *dev, struct fb_info *info)
  {
  	int retval = -ENOMEM;
  	int old_len = info->fix.smem_len;
  	int new_len;
  	unsigned char *old_fb = info->screen_base;
  	unsigned char *new_fb;

  	unsigned char *new_back = 0;

  	pr_warn("Reallocating framebuffer. Addresses will change!
  ");

  
  	new_len = info->fix.line_length * info->var.yres;
  
  	if (PAGE_ALIGN(new_len) > old_len) {
  		/*
  		 * Alloc system memory for virtual framebuffer
  		 */
  		new_fb = vmalloc(new_len);
  		if (!new_fb) {

  			pr_err("Virtual framebuffer alloc failed
  ");

  			goto error;
  		}
  
  		if (info->screen_base) {
  			memcpy(new_fb, old_fb, old_len);
  			vfree(info->screen_base);
  		}
  
  		info->screen_base = new_fb;
  		info->fix.smem_len = PAGE_ALIGN(new_len);
  		info->fix.smem_start = (unsigned long) new_fb;
  		info->flags = udlfb_info_flags;
  
  		/*
  		 * Second framebuffer copy to mirror the framebuffer state
  		 * on the physical USB device. We can function without this.
  		 * But with imperfect damage info we may send pixels over USB
  		 * that were, in fact, unchanged - wasting limited USB bandwidth
  		 */

  		if (shadow)
  			new_back = vzalloc(new_len);

  		if (!new_back)

  			pr_info("No shadow/backing buffer allocated
  ");

  		else {
  			if (dev->backing_buffer)
  				vfree(dev->backing_buffer);
  			dev->backing_buffer = new_back;

  		}
  	}
  
  	retval = 0;
  
  error:
  	return retval;
  }
  
  /*
   * 1) Get EDID from hw, or use sw default
   * 2) Parse into various fb_info structs
   * 3) Allocate virtual framebuffer memory to back highest res mode
   *
   * Parses EDID into three places used by various parts of fbdev:

   * fb_var_screeninfo contains the timing of the monitor's preferred mode
   * fb_info.monspecs is full parsed EDID info, including monspecs.modedb
   * fb_info.modelist is a linked list of all monitor & VESA modes which work
   *
   * If EDID is not readable/valid, then modelist is all VESA modes,
   * monspecs is NULL, and fb_var_screeninfo is set to safe VESA mode

   * Returns 0 if successful

   */

  static int dlfb_setup_modes(struct dlfb_data *dev,
  			   struct fb_info *info,
  			   char *default_edid, size_t default_edid_size)

  {
  	int i;
  	const struct fb_videomode *default_vmode = NULL;
  	int result = 0;

  	char *edid;
  	int tries = 3;
  
  	if (info->dev) /* only use mutex if info has been registered */
  		mutex_lock(&info->lock);

  	edid = kmalloc(EDID_LENGTH, GFP_KERNEL);

  	if (!edid) {
  		result = -ENOMEM;
  		goto error;
  	}

  
  	fb_destroy_modelist(&info->modelist);
  	memset(&info->monspecs, 0, sizeof(info->monspecs));

  	/*
  	 * Try to (re)read EDID from hardware first
  	 * EDID data may return, but not parse as valid
  	 * Try again a few times, in case of e.g. analog cable noise
  	 */
  	while (tries--) {

  		i = dlfb_get_edid(dev, edid, EDID_LENGTH);

  		if (i >= EDID_LENGTH)

  			fb_edid_to_monspecs(edid, &info->monspecs);
  
  		if (info->monspecs.modedb_len > 0) {
  			dev->edid = edid;
  			dev->edid_size = i;
  			break;
  		}
  	}
  
  	/* If that fails, use a previously returned EDID if available */
  	if (info->monspecs.modedb_len == 0) {

  		pr_err("Unable to get valid EDID from device/display
  ");

  
  		if (dev->edid) {
  			fb_edid_to_monspecs(dev->edid, &info->monspecs);
  			if (info->monspecs.modedb_len > 0)

  				pr_err("Using previously queried EDID
  ");

  		}
  	}
  
  	/* If that fails, use the default EDID we were handed */
  	if (info->monspecs.modedb_len == 0) {

  		if (default_edid_size >= EDID_LENGTH) {

  			fb_edid_to_monspecs(default_edid, &info->monspecs);
  			if (info->monspecs.modedb_len > 0) {
  				memcpy(edid, default_edid, default_edid_size);
  				dev->edid = edid;
  				dev->edid_size = default_edid_size;

  				pr_err("Using default/backup EDID
  ");

  			}
  		}
  	}

  	/* If we've got modes, let's pick a best default mode */

  	if (info->monspecs.modedb_len > 0) {
  
  		for (i = 0; i < info->monspecs.modedb_len; i++) {
  			if (dlfb_is_valid_mode(&info->monspecs.modedb[i], info))
  				fb_add_videomode(&info->monspecs.modedb[i],
  					&info->modelist);

  			else {
  				if (i == 0)
  					/* if we've removed top/best mode */
  					info->monspecs.misc
  						&= ~FB_MISC_1ST_DETAIL;
  			}

  		}
  
  		default_vmode = fb_find_best_display(&info->monspecs,
  						     &info->modelist);

  	}

  	/* If everything else has failed, fall back to safe default mode */
  	if (default_vmode == NULL) {
  
  		struct fb_videomode fb_vmode = {0};

  
  		/*
  		 * Add the standard VESA modes to our modelist
  		 * Since we don't have EDID, there may be modes that
  		 * overspec monitor and/or are incorrect aspect ratio, etc.
  		 * But at least the user has a chance to choose
  		 */
  		for (i = 0; i < VESA_MODEDB_SIZE; i++) {
  			if (dlfb_is_valid_mode((struct fb_videomode *)
  						&vesa_modes[i], info))
  				fb_add_videomode(&vesa_modes[i],
  						 &info->modelist);
  		}
  
  		/*
  		 * default to resolution safe for projectors
  		 * (since they are most common case without EDID)
  		 */
  		fb_vmode.xres = 800;
  		fb_vmode.yres = 600;
  		fb_vmode.refresh = 60;
  		default_vmode = fb_find_nearest_mode(&fb_vmode,
  						     &info->modelist);
  	}

  	/* If we have good mode and no active clients*/
  	if ((default_vmode != NULL) && (dev->fb_count == 0)) {
  
  		fb_videomode_to_var(&info->var, default_vmode);
  		dlfb_var_color_format(&info->var);
  
  		/*
  		 * with mode size info, we can now alloc our framebuffer.
  		 */
  		memcpy(&info->fix, &dlfb_fix, sizeof(dlfb_fix));
  		info->fix.line_length = info->var.xres *
  			(info->var.bits_per_pixel / 8);
  
  		result = dlfb_realloc_framebuffer(dev, info);
  
  	} else
  		result = -EINVAL;
  
  error:
  	if (edid && (dev->edid != edid))
  		kfree(edid);
  
  	if (info->dev)
  		mutex_unlock(&info->lock);

  
  	return result;
  }
  
  static ssize_t metrics_bytes_rendered_show(struct device *fbdev,
  				   struct device_attribute *a, char *buf) {
  	struct fb_info *fb_info = dev_get_drvdata(fbdev);
  	struct dlfb_data *dev = fb_info->par;
  	return snprintf(buf, PAGE_SIZE, "%u
  ",
  			atomic_read(&dev->bytes_rendered));
  }
  
  static ssize_t metrics_bytes_identical_show(struct device *fbdev,
  				   struct device_attribute *a, char *buf) {
  	struct fb_info *fb_info = dev_get_drvdata(fbdev);
  	struct dlfb_data *dev = fb_info->par;
  	return snprintf(buf, PAGE_SIZE, "%u
  ",
  			atomic_read(&dev->bytes_identical));
  }
  
  static ssize_t metrics_bytes_sent_show(struct device *fbdev,
  				   struct device_attribute *a, char *buf) {
  	struct fb_info *fb_info = dev_get_drvdata(fbdev);
  	struct dlfb_data *dev = fb_info->par;
  	return snprintf(buf, PAGE_SIZE, "%u
  ",
  			atomic_read(&dev->bytes_sent));
  }
  
  static ssize_t metrics_cpu_kcycles_used_show(struct device *fbdev,
  				   struct device_attribute *a, char *buf) {
  	struct fb_info *fb_info = dev_get_drvdata(fbdev);
  	struct dlfb_data *dev = fb_info->par;
  	return snprintf(buf, PAGE_SIZE, "%u
  ",
  			atomic_read(&dev->cpu_kcycles_used));
  }

  static ssize_t edid_show(
  			struct file *filp,
  			struct kobject *kobj, struct bin_attribute *a,

  			 char *buf, loff_t off, size_t count) {
  	struct device *fbdev = container_of(kobj, struct device, kobj);
  	struct fb_info *fb_info = dev_get_drvdata(fbdev);
  	struct dlfb_data *dev = fb_info->par;

  	if (dev->edid == NULL)

  		return 0;

  	if ((off >= dev->edid_size) || (count > dev->edid_size))

  		return 0;

  	if (off + count > dev->edid_size)
  		count = dev->edid_size - off;

  	pr_info("sysfs edid copy %p to %p, %d bytes
  ",

  		dev->edid, buf, (int) count);
  
  	memcpy(buf, dev->edid, count);

  
  	return count;
  }

  static ssize_t edid_store(
  			struct file *filp,
  			struct kobject *kobj, struct bin_attribute *a,
  			char *src, loff_t src_off, size_t src_size) {
  	struct device *fbdev = container_of(kobj, struct device, kobj);
  	struct fb_info *fb_info = dev_get_drvdata(fbdev);
  	struct dlfb_data *dev = fb_info->par;
  
  	/* We only support write of entire EDID at once, no offset*/

  	if ((src_size != EDID_LENGTH) || (src_off != 0))

  		return 0;
  
  	dlfb_setup_modes(dev, fb_info, src, src_size);
  
  	if (dev->edid && (memcmp(src, dev->edid, src_size) == 0)) {

  		pr_info("sysfs written EDID is new default
  ");

  		dlfb_ops_set_par(fb_info);
  		return src_size;
  	} else
  		return 0;
  }

  
  static ssize_t metrics_reset_store(struct device *fbdev,
  			   struct device_attribute *attr,
  			   const char *buf, size_t count)
  {
  	struct fb_info *fb_info = dev_get_drvdata(fbdev);
  	struct dlfb_data *dev = fb_info->par;
  
  	atomic_set(&dev->bytes_rendered, 0);
  	atomic_set(&dev->bytes_identical, 0);
  	atomic_set(&dev->bytes_sent, 0);
  	atomic_set(&dev->cpu_kcycles_used, 0);

  
  	return count;
  }

  static struct bin_attribute edid_attr = {
  	.attr.name = "edid",

  	.attr.mode = 0666,

  	.size = EDID_LENGTH,

  	.read = edid_show,

  	.write = edid_store

  };
  
  static struct device_attribute fb_device_attrs[] = {
  	__ATTR_RO(metrics_bytes_rendered),
  	__ATTR_RO(metrics_bytes_identical),
  	__ATTR_RO(metrics_bytes_sent),
  	__ATTR_RO(metrics_cpu_kcycles_used),

  	__ATTR(metrics_reset, S_IWUSR, NULL, metrics_reset_store),

  };
  
  /*

   * This is necessary before we can communicate with the display controller.
   */
  static int dlfb_select_std_channel(struct dlfb_data *dev)
  {
  	int ret;
  	u8 set_def_chn[] = {	   0x57, 0xCD, 0xDC, 0xA7,
  				0x1C, 0x88, 0x5E, 0x15,
  				0x60, 0xFE, 0xC6, 0x97,
  				0x16, 0x3D, 0x47, 0xF2  };
  
  	ret = usb_control_msg(dev->udev, usb_sndctrlpipe(dev->udev, 0),
  			NR_USB_REQUEST_CHANNEL,
  			(USB_DIR_OUT | USB_TYPE_VENDOR), 0, 0,
  			set_def_chn, sizeof(set_def_chn), USB_CTRL_SET_TIMEOUT);
  	return ret;
  }

  static int dlfb_parse_vendor_descriptor(struct dlfb_data *dev,

  					struct usb_interface *interface)

  {
  	char *desc;
  	char *buf;
  	char *desc_end;

  	int total_len = 0;

  
  	buf = kzalloc(MAX_VENDOR_DESCRIPTOR_SIZE, GFP_KERNEL);
  	if (!buf)
  		return false;
  	desc = buf;

  	total_len = usb_get_descriptor(interface_to_usbdev(interface),
  					0x5f, /* vendor specific */
  					0, desc, MAX_VENDOR_DESCRIPTOR_SIZE);
  
  	/* if not found, look in configuration descriptor */
  	if (total_len < 0) {
  		if (0 == usb_get_extra_descriptor(interface->cur_altsetting,
  			0x5f, &desc))
  			total_len = (int) desc[0];
  	}

  	if (total_len > 5) {

  		pr_info("vendor descriptor length:%x data:%02x %02x %02x %02x" \

  			"%02x %02x %02x %02x %02x %02x %02x
  ",
  			total_len, desc[0],
  			desc[1], desc[2], desc[3], desc[4], desc[5], desc[6],
  			desc[7], desc[8], desc[9], desc[10]);
  
  		if ((desc[0] != total_len) || /* descriptor length */
  		    (desc[1] != 0x5f) ||   /* vendor descriptor type */
  		    (desc[2] != 0x01) ||   /* version (2 bytes) */
  		    (desc[3] != 0x00) ||
  		    (desc[4] != total_len - 2)) /* length after type */
  			goto unrecognized;
  
  		desc_end = desc + total_len;
  		desc += 5; /* the fixed header we've already parsed */
  
  		while (desc < desc_end) {
  			u8 length;
  			u16 key;
  
  			key = *((u16 *) desc);
  			desc += sizeof(u16);
  			length = *desc;
  			desc++;
  
  			switch (key) {
  			case 0x0200: { /* max_area */
  				u32 max_area;
  				max_area = le32_to_cpu(*((u32 *)desc));

  				pr_warn("DL chip limited to %d pixel modes
  ",

  					max_area);
  				dev->sku_pixel_limit = max_area;
  				break;
  			}
  			default:
  				break;
  			}
  			desc += length;
  		}

  	} else {
  		pr_info("vendor descriptor not available (%d)
  ", total_len);

  	}
  
  	goto success;

  unrecognized:
  	/* allow udlfb to load for now even if firmware unrecognized */

  	pr_err("Unrecognized vendor firmware descriptor
  ");

  
  success:
  	kfree(buf);
  	return true;
  }

  static int dlfb_usb_probe(struct usb_interface *interface,

  			const struct usb_device_id *id)

  {

  	struct usb_device *usbdev;

  	struct dlfb_data *dev = 0;

  	struct fb_info *info = 0;

  	int retval = -ENOMEM;

  	int i;

  	/* usb initialization */
  
  	usbdev = interface_to_usbdev(interface);

  
  	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
  	if (dev == NULL) {

  		err("dlfb_usb_probe: failed alloc of dev struct
  ");
  		goto error;

  	}

  	/* we need to wait for both usb and fbdev to spin down on disconnect */
  	kref_init(&dev->kref); /* matching kref_put in usb .disconnect fn */

  	kref_get(&dev->kref); /* matching kref_put in free_framebuffer_work */

  	dev->udev = usbdev;

  	dev->gdev = &usbdev->dev; /* our generic struct device * */

  	usb_set_intfdata(interface, dev);

  	pr_info("%s %s - serial #%s
  ",

  		usbdev->manufacturer, usbdev->product, usbdev->serial);

  	pr_info("vid_%04x&pid_%04x&rev_%04x driver's dlfb_data struct at %p
  ",

  		usbdev->descriptor.idVendor, usbdev->descriptor.idProduct,
  		usbdev->descriptor.bcdDevice, dev);

  	pr_info("console enable=%d
  ", console);
  	pr_info("fb_defio enable=%d
  ", fb_defio);

  	pr_info("shadow enable=%d
  ", shadow);

  
  	dev->sku_pixel_limit = 2048 * 1152; /* default to maximum */

  	if (!dlfb_parse_vendor_descriptor(dev, interface)) {

  		pr_err("firmware not recognized. Assume incompatible device
  ");

  		goto error;
  	}

  	if (!dlfb_alloc_urb_list(dev, WRITES_IN_FLIGHT, MAX_TRANSFER)) {
  		retval = -ENOMEM;

  		pr_err("dlfb_alloc_urb_list failed
  ");

  		goto error;
  	}

  	/* We don't register a new USB class. Our client interface is fbdev */

  	/* allocates framebuffer driver structure, not framebuffer memory */

  	info = framebuffer_alloc(0, &interface->dev);

  	if (!info) {
  		retval = -ENOMEM;

  		pr_err("framebuffer_alloc failed
  ");

  		goto error;
  	}

  	dev->info = info;
  	info->par = dev;
  	info->pseudo_palette = dev->pseudo_palette;

  	info->fbops = &dlfb_ops;

  	retval = fb_alloc_cmap(&info->cmap, 256, 0);
  	if (retval < 0) {

  		pr_err("fb_alloc_cmap failed %x
  ", retval);

  		goto error;
  	}

  	INIT_DELAYED_WORK(&dev->free_framebuffer_work,
  			  dlfb_free_framebuffer_work);

  	INIT_LIST_HEAD(&info->modelist);
  
  	retval = dlfb_setup_modes(dev, info, NULL, 0);
  	if (retval != 0) {

  		pr_err("unable to find common mode for display and adapter
  ");

  		goto error;
  	}

  	/* ready to begin using device */

  	atomic_set(&dev->usb_active, 1);
  	dlfb_select_std_channel(dev);

  	dlfb_ops_check_var(&info->var, info);

  	dlfb_ops_set_par(info);

  	retval = register_framebuffer(info);

  	if (retval < 0) {

  		pr_err("register_framebuffer failed %d
  ", retval);

  		goto error;

  	}

  	for (i = 0; i < ARRAY_SIZE(fb_device_attrs); i++) {
  		retval = device_create_file(info->dev, &fb_device_attrs[i]);
  		if (retval) {
  			pr_err("device_create_file failed %d
  ", retval);
  			goto err_del_attrs;
  		}
  	}

  	retval = device_create_bin_file(info->dev, &edid_attr);
  	if (retval) {
  		pr_err("device_create_bin_file failed %d
  ", retval);
  		goto err_del_attrs;
  	}

  	pr_info("DisplayLink USB device /dev/fb%d attached. %dx%d resolution."

  			" Using %dK framebuffer memory
  ", info->node,

  			info->var.xres, info->var.yres,

  			((dev->backing_buffer) ?

  			info->fix.smem_len * 2 : info->fix.smem_len) >> 10);

  	return 0;

  err_del_attrs:
  	for (i -= 1; i >= 0; i--)
  		device_remove_file(info->dev, &fb_device_attrs[i]);

  error:
  	if (dev) {

  		if (info) {
  			if (info->cmap.len != 0)
  				fb_dealloc_cmap(&info->cmap);
  			if (info->monspecs.modedb)
  				fb_destroy_modedb(info->monspecs.modedb);
  			if (info->screen_base)
  				vfree(info->screen_base);
  
  			fb_destroy_modelist(&info->modelist);
  
  			framebuffer_release(info);
  		}
  
  		if (dev->backing_buffer)
  			vfree(dev->backing_buffer);
  
  		kref_put(&dev->kref, dlfb_free); /* ref for framebuffer */
  		kref_put(&dev->kref, dlfb_free); /* last ref from kref_init */

  
  		/* dev has been deallocated. Do not dereference */
  	}

  	return retval;

  }

  static void dlfb_usb_disconnect(struct usb_interface *interface)

  {

  	struct dlfb_data *dev;
  	struct fb_info *info;

  	int i;

  	dev = usb_get_intfdata(interface);

  	info = dev->info;

  	pr_info("USB disconnect starting
  ");

  	/* we virtualize until all fb clients release. Then we free */
  	dev->virtualized = true;
  
  	/* When non-active we'll update virtual framebuffer, but no new urbs */
  	atomic_set(&dev->usb_active, 0);

  	/* remove udlfb's sysfs interfaces */

  	for (i = 0; i < ARRAY_SIZE(fb_device_attrs); i++)
  		device_remove_file(info->dev, &fb_device_attrs[i]);

  	device_remove_bin_file(info->dev, &edid_attr);

  	usb_set_intfdata(interface, NULL);

  	/* if clients still have us open, will be freed on last close */
  	if (dev->fb_count == 0)
  		schedule_delayed_work(&dev->free_framebuffer_work, 0);

  	/* release reference taken by kref_init in probe() */

  	kref_put(&dev->kref, dlfb_free);

  	/* consider dlfb_data freed */
  
  	return;

  }
  
  static struct usb_driver dlfb_driver = {
  	.name = "udlfb",

  	.probe = dlfb_usb_probe,
  	.disconnect = dlfb_usb_disconnect,

  	.id_table = id_table,
  };

  module_usb_driver(dlfb_driver);

  static void dlfb_urb_completion(struct urb *urb)
  {
  	struct urb_node *unode = urb->context;
  	struct dlfb_data *dev = unode->dev;
  	unsigned long flags;
  
  	/* sync/async unlink faults aren't errors */
  	if (urb->status) {
  		if (!(urb->status == -ENOENT ||
  		    urb->status == -ECONNRESET ||
  		    urb->status == -ESHUTDOWN)) {

  			pr_err("%s - nonzero write bulk status received: %d
  ",

  				__func__, urb->status);
  			atomic_set(&dev->lost_pixels, 1);
  		}
  	}
  
  	urb->transfer_buffer_length = dev->urbs.size; /* reset to actual */
  
  	spin_lock_irqsave(&dev->urbs.lock, flags);
  	list_add_tail(&unode->entry, &dev->urbs.list);
  	dev->urbs.available++;
  	spin_unlock_irqrestore(&dev->urbs.lock, flags);

  	/*
  	 * When using fb_defio, we deadlock if up() is called
  	 * while another is waiting. So queue to another process.
  	 */
  	if (fb_defio)
  		schedule_delayed_work(&unode->release_urb_work, 0);
  	else
  		up(&dev->urbs.limit_sem);

  }
  
  static void dlfb_free_urb_list(struct dlfb_data *dev)
  {
  	int count = dev->urbs.count;
  	struct list_head *node;
  	struct urb_node *unode;
  	struct urb *urb;
  	int ret;
  	unsigned long flags;

  	pr_notice("Waiting for completes and freeing all render urbs
  ");

  
  	/* keep waiting and freeing, until we've got 'em all */
  	while (count--) {

  
  		/* Getting interrupted means a leak, but ok at shutdown*/
  		ret = down_interruptible(&dev->urbs.limit_sem);
  		if (ret)

  			break;

  		spin_lock_irqsave(&dev->urbs.lock, flags);
  
  		node = dev->urbs.list.next; /* have reserved one with sem */
  		list_del_init(node);
  
  		spin_unlock_irqrestore(&dev->urbs.lock, flags);
  
  		unode = list_entry(node, struct urb_node, entry);
  		urb = unode->urb;
  
  		/* Free each separately allocated piece */

  		usb_free_coherent(urb->dev, dev->urbs.size,
  				  urb->transfer_buffer, urb->transfer_dma);

  		usb_free_urb(urb);
  		kfree(node);
  	}

  }
  
  static int dlfb_alloc_urb_list(struct dlfb_data *dev, int count, size_t size)
  {
  	int i = 0;
  	struct urb *urb;
  	struct urb_node *unode;
  	char *buf;
  
  	spin_lock_init(&dev->urbs.lock);
  
  	dev->urbs.size = size;
  	INIT_LIST_HEAD(&dev->urbs.list);
  
  	while (i < count) {
  		unode = kzalloc(sizeof(struct urb_node), GFP_KERNEL);
  		if (!unode)
  			break;
  		unode->dev = dev;

  		INIT_DELAYED_WORK(&unode->release_urb_work,
  			  dlfb_release_urb_work);

  		urb = usb_alloc_urb(0, GFP_KERNEL);
  		if (!urb) {
  			kfree(unode);
  			break;
  		}
  		unode->urb = urb;

  		buf = usb_alloc_coherent(dev->udev, MAX_TRANSFER, GFP_KERNEL,
  					 &urb->transfer_dma);

  		if (!buf) {
  			kfree(unode);
  			usb_free_urb(urb);
  			break;
  		}
  
  		/* urb->transfer_buffer_length set to actual before submit */
  		usb_fill_bulk_urb(urb, dev->udev, usb_sndbulkpipe(dev->udev, 1),
  			buf, size, dlfb_urb_completion, unode);
  		urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
  
  		list_add_tail(&unode->entry, &dev->urbs.list);
  
  		i++;
  	}
  
  	sema_init(&dev->urbs.limit_sem, i);
  	dev->urbs.count = i;
  	dev->urbs.available = i;

  	pr_notice("allocated %d %d byte urbs
  ", i, (int) size);

  
  	return i;
  }
  
  static struct urb *dlfb_get_urb(struct dlfb_data *dev)
  {
  	int ret = 0;
  	struct list_head *entry;
  	struct urb_node *unode;
  	struct urb *urb = NULL;
  	unsigned long flags;
  
  	/* Wait for an in-flight buffer to complete and get re-queued */
  	ret = down_timeout(&dev->urbs.limit_sem, GET_URB_TIMEOUT);
  	if (ret) {
  		atomic_set(&dev->lost_pixels, 1);

  		pr_warn("wait for urb interrupted: %x available: %d
  ",

  		       ret, dev->urbs.available);

  		goto error;
  	}
  
  	spin_lock_irqsave(&dev->urbs.lock, flags);
  
  	BUG_ON(list_empty(&dev->urbs.list)); /* reserved one with limit_sem */
  	entry = dev->urbs.list.next;
  	list_del_init(entry);
  	dev->urbs.available--;
  
  	spin_unlock_irqrestore(&dev->urbs.lock, flags);
  
  	unode = list_entry(entry, struct urb_node, entry);
  	urb = unode->urb;
  
  error:
  	return urb;
  }
  
  static int dlfb_submit_urb(struct dlfb_data *dev, struct urb *urb, size_t len)
  {
  	int ret;
  
  	BUG_ON(len > dev->urbs.size);
  
  	urb->transfer_buffer_length = len; /* set to actual payload len */
  	ret = usb_submit_urb(urb, GFP_KERNEL);
  	if (ret) {
  		dlfb_urb_completion(urb); /* because no one else will */
  		atomic_set(&dev->lost_pixels, 1);

  		pr_err("usb_submit_urb error %x
  ", ret);

  	}
  	return ret;
  }

  module_param(console, bool, S_IWUSR | S_IRUSR | S_IWGRP | S_IRGRP);

  MODULE_PARM_DESC(console, "Allow fbcon to open framebuffer");

  
  module_param(fb_defio, bool, S_IWUSR | S_IRUSR | S_IWGRP | S_IRGRP);

  MODULE_PARM_DESC(fb_defio, "Page fault detection of mmap writes");

  module_param(shadow, bool, S_IWUSR | S_IRUSR | S_IWGRP | S_IRGRP);
  MODULE_PARM_DESC(shadow, "Shadow vid mem. Disable to save mem but lose perf");

  MODULE_AUTHOR("Roberto De Ioris <roberto@unbit.it>, "

  	      "Jaya Kumar <jayakumar.lkml@gmail.com>, "
  	      "Bernie Thompson <bernie@plugable.com>");
  MODULE_DESCRIPTION("DisplayLink kernel framebuffer driver");

  MODULE_LICENSE("GPL");