serial-u16550.c 30.8 KB
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050
/*
 *   serial.c
 *   Copyright (c) by Jaroslav Kysela <perex@perex.cz>,
 *                    Isaku Yamahata <yamahata@private.email.ne.jp>,
 *		      George Hansper <ghansper@apana.org.au>,
 *		      Hannu Savolainen
 *
 *   This code is based on the code from ALSA 0.5.9, but heavily rewritten.
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 *
 * Sat Mar 31 17:27:57 PST 2001 tim.mann@compaq.com 
 *      Added support for the Midiator MS-124T and for the MS-124W in
 *      Single Addressed (S/A) or Multiple Burst (M/B) mode, with
 *      power derived either parasitically from the serial port or
 *      from a separate power supply.
 *
 *      More documentation can be found in serial-u16550.txt.
 */

#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/err.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/ioport.h>
#include <linux/module.h>
#include <sound/core.h>
#include <sound/rawmidi.h>
#include <sound/initval.h>

#include <linux/serial_reg.h>
#include <linux/jiffies.h>

#include <asm/io.h>

MODULE_DESCRIPTION("MIDI serial u16550");
MODULE_LICENSE("GPL");
MODULE_SUPPORTED_DEVICE("{{ALSA, MIDI serial u16550}}");

#define SNDRV_SERIAL_SOUNDCANVAS 0 /* Roland Soundcanvas; F5 NN selects part */
#define SNDRV_SERIAL_MS124T 1      /* Midiator MS-124T */
#define SNDRV_SERIAL_MS124W_SA 2   /* Midiator MS-124W in S/A mode */
#define SNDRV_SERIAL_MS124W_MB 3   /* Midiator MS-124W in M/B mode */
#define SNDRV_SERIAL_GENERIC 4     /* Generic Interface */
#define SNDRV_SERIAL_MAX_ADAPTOR SNDRV_SERIAL_GENERIC
static char *adaptor_names[] = {
	"Soundcanvas",
        "MS-124T",
	"MS-124W S/A",
	"MS-124W M/B",
	"Generic"
};

#define SNDRV_SERIAL_NORMALBUFF 0 /* Normal blocking buffer operation */
#define SNDRV_SERIAL_DROPBUFF   1 /* Non-blocking discard operation */

static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX;	/* Index 0-MAX */
static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR;	/* ID for this card */
static bool enable[SNDRV_CARDS] = SNDRV_DEFAULT_ENABLE; /* Enable this card */
static long port[SNDRV_CARDS] = SNDRV_DEFAULT_PORT; /* 0x3f8,0x2f8,0x3e8,0x2e8 */
static int irq[SNDRV_CARDS] = SNDRV_DEFAULT_IRQ; 	/* 3,4,5,7,9,10,11,14,15 */
static int speed[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS - 1)] = 38400}; /* 9600,19200,38400,57600,115200 */
static int base[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS - 1)] = 115200}; /* baud base */
static int outs[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS - 1)] = 1};	 /* 1 to 16 */
static int ins[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS - 1)] = 1};	/* 1 to 16 */
static int adaptor[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS - 1)] = SNDRV_SERIAL_SOUNDCANVAS};
static bool droponfull[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS -1)] = SNDRV_SERIAL_NORMALBUFF };

module_param_array(index, int, NULL, 0444);
MODULE_PARM_DESC(index, "Index value for Serial MIDI.");
module_param_array(id, charp, NULL, 0444);
MODULE_PARM_DESC(id, "ID string for Serial MIDI.");
module_param_array(enable, bool, NULL, 0444);
MODULE_PARM_DESC(enable, "Enable UART16550A chip.");
module_param_array(port, long, NULL, 0444);
MODULE_PARM_DESC(port, "Port # for UART16550A chip.");
module_param_array(irq, int, NULL, 0444);
MODULE_PARM_DESC(irq, "IRQ # for UART16550A chip.");
module_param_array(speed, int, NULL, 0444);
MODULE_PARM_DESC(speed, "Speed in bauds.");
module_param_array(base, int, NULL, 0444);
MODULE_PARM_DESC(base, "Base for divisor in bauds.");
module_param_array(outs, int, NULL, 0444);
MODULE_PARM_DESC(outs, "Number of MIDI outputs.");
module_param_array(ins, int, NULL, 0444);
MODULE_PARM_DESC(ins, "Number of MIDI inputs.");
module_param_array(droponfull, bool, NULL, 0444);
MODULE_PARM_DESC(droponfull, "Flag to enable drop-on-full buffer mode");

module_param_array(adaptor, int, NULL, 0444);
MODULE_PARM_DESC(adaptor, "Type of adaptor.");

/*#define SNDRV_SERIAL_MS124W_MB_NOCOMBO 1*/  /* Address outs as 0-3 instead of bitmap */

#define SNDRV_SERIAL_MAX_OUTS	16		/* max 64, min 16 */
#define SNDRV_SERIAL_MAX_INS	16		/* max 64, min 16 */

#define TX_BUFF_SIZE		(1<<15)		/* Must be 2^n */
#define TX_BUFF_MASK		(TX_BUFF_SIZE - 1)

#define SERIAL_MODE_NOT_OPENED 		(0)
#define SERIAL_MODE_INPUT_OPEN		(1 << 0)
#define SERIAL_MODE_OUTPUT_OPEN		(1 << 1)
#define SERIAL_MODE_INPUT_TRIGGERED	(1 << 2)
#define SERIAL_MODE_OUTPUT_TRIGGERED	(1 << 3)

struct snd_uart16550 {
	struct snd_card *card;
	struct snd_rawmidi *rmidi;
	struct snd_rawmidi_substream *midi_output[SNDRV_SERIAL_MAX_OUTS];
	struct snd_rawmidi_substream *midi_input[SNDRV_SERIAL_MAX_INS];

	int filemode;		/* open status of file */

	spinlock_t open_lock;

	int irq;

	unsigned long base;
	struct resource *res_base;

	unsigned int speed;
	unsigned int speed_base;
	unsigned char divisor;

	unsigned char old_divisor_lsb;
	unsigned char old_divisor_msb;
	unsigned char old_line_ctrl_reg;

	/* parameter for using of write loop */
	short int fifo_limit;	/* used in uart16550 */
        short int fifo_count;	/* used in uart16550 */

	/* type of adaptor */
	int adaptor;

	/* inputs */
	int prev_in;
	unsigned char rstatus;

	/* outputs */
	int prev_out;
	unsigned char prev_status[SNDRV_SERIAL_MAX_OUTS];

	/* write buffer and its writing/reading position */
	unsigned char tx_buff[TX_BUFF_SIZE];
	int buff_in_count;
        int buff_in;
        int buff_out;
        int drop_on_full;

	/* wait timer */
	unsigned int timer_running:1;
	struct timer_list buffer_timer;

};

static struct platform_device *devices[SNDRV_CARDS];

static inline void snd_uart16550_add_timer(struct snd_uart16550 *uart)
{
	if (!uart->timer_running) {
		/* timer 38600bps * 10bit * 16byte */
		uart->buffer_timer.expires = jiffies + (HZ+255)/256;
		uart->timer_running = 1;
		add_timer(&uart->buffer_timer);
	}
}

static inline void snd_uart16550_del_timer(struct snd_uart16550 *uart)
{
	if (uart->timer_running) {
		del_timer(&uart->buffer_timer);
		uart->timer_running = 0;
	}
}

/* This macro is only used in snd_uart16550_io_loop */
static inline void snd_uart16550_buffer_output(struct snd_uart16550 *uart)
{
	unsigned short buff_out = uart->buff_out;
	if (uart->buff_in_count > 0) {
		outb(uart->tx_buff[buff_out], uart->base + UART_TX);
		uart->fifo_count++;
		buff_out++;
		buff_out &= TX_BUFF_MASK;
		uart->buff_out = buff_out;
		uart->buff_in_count--;
	}
}

/* This loop should be called with interrupts disabled
 * We don't want to interrupt this, 
 * as we're already handling an interrupt 
 */
static void snd_uart16550_io_loop(struct snd_uart16550 * uart)
{
	unsigned char c, status;
	int substream;

	/* recall previous stream */
	substream = uart->prev_in;

	/* Read Loop */
	while ((status = inb(uart->base + UART_LSR)) & UART_LSR_DR) {
		/* while receive data ready */
		c = inb(uart->base + UART_RX);

		/* keep track of last status byte */
		if (c & 0x80)
			uart->rstatus = c;

		/* handle stream switch */
		if (uart->adaptor == SNDRV_SERIAL_GENERIC) {
			if (uart->rstatus == 0xf5) {
				if (c <= SNDRV_SERIAL_MAX_INS && c > 0)
					substream = c - 1;
				if (c != 0xf5)
					/* prevent future bytes from being
					   interpreted as streams */
					uart->rstatus = 0;
			} else if ((uart->filemode & SERIAL_MODE_INPUT_OPEN)
				   && uart->midi_input[substream])
				snd_rawmidi_receive(uart->midi_input[substream],
						    &c, 1);
		} else if ((uart->filemode & SERIAL_MODE_INPUT_OPEN) &&
			   uart->midi_input[substream])
			snd_rawmidi_receive(uart->midi_input[substream], &c, 1);

		if (status & UART_LSR_OE)
			snd_printk(KERN_WARNING
				   "%s: Overrun on device at 0x%lx\n",
			       uart->rmidi->name, uart->base);
	}

	/* remember the last stream */
	uart->prev_in = substream;

	/* no need of check SERIAL_MODE_OUTPUT_OPEN because if not,
	   buffer is never filled. */
	/* Check write status */
	if (status & UART_LSR_THRE)
		uart->fifo_count = 0;
	if (uart->adaptor == SNDRV_SERIAL_MS124W_SA
	   || uart->adaptor == SNDRV_SERIAL_GENERIC) {
		/* Can't use FIFO, must send only when CTS is true */
		status = inb(uart->base + UART_MSR);
		while (uart->fifo_count == 0 && (status & UART_MSR_CTS) &&
		       uart->buff_in_count > 0) {
		       snd_uart16550_buffer_output(uart);
		       status = inb(uart->base + UART_MSR);
		}
	} else {
		/* Write loop */
		while (uart->fifo_count < uart->fifo_limit /* Can we write ? */
		       && uart->buff_in_count > 0)	/* Do we want to? */
			snd_uart16550_buffer_output(uart);
	}
	if (uart->irq < 0 && uart->buff_in_count > 0)
		snd_uart16550_add_timer(uart);
}

/* NOTES ON SERVICING INTERUPTS
 * ---------------------------
 * After receiving a interrupt, it is important to indicate to the UART that
 * this has been done. 
 * For a Rx interrupt, this is done by reading the received byte.
 * For a Tx interrupt this is done by either:
 * a) Writing a byte
 * b) Reading the IIR
 * It is particularly important to read the IIR if a Tx interrupt is received
 * when there is no data in tx_buff[], as in this case there no other
 * indication that the interrupt has been serviced, and it remains outstanding
 * indefinitely. This has the curious side effect that and no further interrupts
 * will be generated from this device AT ALL!!.
 * It is also desirable to clear outstanding interrupts when the device is
 * opened/closed.
 *
 *
 * Note that some devices need OUT2 to be set before they will generate
 * interrupts at all. (Possibly tied to an internal pull-up on CTS?)
 */
static irqreturn_t snd_uart16550_interrupt(int irq, void *dev_id)
{
	struct snd_uart16550 *uart;

	uart = dev_id;
	spin_lock(&uart->open_lock);
	if (uart->filemode == SERIAL_MODE_NOT_OPENED) {
		spin_unlock(&uart->open_lock);
		return IRQ_NONE;
	}
	/* indicate to the UART that the interrupt has been serviced */
	inb(uart->base + UART_IIR);
	snd_uart16550_io_loop(uart);
	spin_unlock(&uart->open_lock);
	return IRQ_HANDLED;
}

/* When the polling mode, this function calls snd_uart16550_io_loop. */
static void snd_uart16550_buffer_timer(unsigned long data)
{
	unsigned long flags;
	struct snd_uart16550 *uart;

	uart = (struct snd_uart16550 *)data;
	spin_lock_irqsave(&uart->open_lock, flags);
	snd_uart16550_del_timer(uart);
	snd_uart16550_io_loop(uart);
	spin_unlock_irqrestore(&uart->open_lock, flags);
}

/*
 *  this method probes, if an uart sits on given port
 *  return 0 if found
 *  return negative error if not found
 */
static int snd_uart16550_detect(struct snd_uart16550 *uart)
{
	unsigned long io_base = uart->base;
	int ok;
	unsigned char c;

	/* Do some vague tests for the presence of the uart */
	if (io_base == 0 || io_base == SNDRV_AUTO_PORT) {
		return -ENODEV;	/* Not configured */
	}

	uart->res_base = request_region(io_base, 8, "Serial MIDI");
	if (uart->res_base == NULL) {
		snd_printk(KERN_ERR "u16550: can't grab port 0x%lx\n", io_base);
		return -EBUSY;
	}

	/* uart detected unless one of the following tests should fail */
	ok = 1;
	/* 8 data-bits, 1 stop-bit, parity off, DLAB = 0 */
	outb(UART_LCR_WLEN8, io_base + UART_LCR); /* Line Control Register */
	c = inb(io_base + UART_IER);
	/* The top four bits of the IER should always == 0 */
	if ((c & 0xf0) != 0)
		ok = 0;		/* failed */

	outb(0xaa, io_base + UART_SCR);
	/* Write arbitrary data into the scratch reg */
	c = inb(io_base + UART_SCR);
	/* If it comes back, it's OK */
	if (c != 0xaa)
		ok = 0;		/* failed */

	outb(0x55, io_base + UART_SCR);
	/* Write arbitrary data into the scratch reg */
	c = inb(io_base + UART_SCR);
	/* If it comes back, it's OK */
	if (c != 0x55)
		ok = 0;		/* failed */

	return ok;
}

static void snd_uart16550_do_open(struct snd_uart16550 * uart)
{
	char byte;

	/* Initialize basic variables */
	uart->buff_in_count = 0;
	uart->buff_in = 0;
	uart->buff_out = 0;
	uart->fifo_limit = 1;
	uart->fifo_count = 0;
	uart->timer_running = 0;

	outb(UART_FCR_ENABLE_FIFO	/* Enable FIFO's (if available) */
	     | UART_FCR_CLEAR_RCVR	/* Clear receiver FIFO */
	     | UART_FCR_CLEAR_XMIT	/* Clear transmitter FIFO */
	     | UART_FCR_TRIGGER_4	/* Set FIFO trigger at 4-bytes */
	/* NOTE: interrupt generated after T=(time)4-bytes
	 * if less than UART_FCR_TRIGGER bytes received
	 */
	     ,uart->base + UART_FCR);	/* FIFO Control Register */

	if ((inb(uart->base + UART_IIR) & 0xf0) == 0xc0)
		uart->fifo_limit = 16;
	if (uart->divisor != 0) {
		uart->old_line_ctrl_reg = inb(uart->base + UART_LCR);
		outb(UART_LCR_DLAB	/* Divisor latch access bit */
		     ,uart->base + UART_LCR);	/* Line Control Register */
		uart->old_divisor_lsb = inb(uart->base + UART_DLL);
		uart->old_divisor_msb = inb(uart->base + UART_DLM);

		outb(uart->divisor
		     ,uart->base + UART_DLL);	/* Divisor Latch Low */
		outb(0
		     ,uart->base + UART_DLM);	/* Divisor Latch High */
		/* DLAB is reset to 0 in next outb() */
	}
	/* Set serial parameters (parity off, etc) */
	outb(UART_LCR_WLEN8	/* 8 data-bits */
	     | 0		/* 1 stop-bit */
	     | 0		/* parity off */
	     | 0		/* DLAB = 0 */
	     ,uart->base + UART_LCR);	/* Line Control Register */

	switch (uart->adaptor) {
	default:
		outb(UART_MCR_RTS	/* Set Request-To-Send line active */
		     | UART_MCR_DTR	/* Set Data-Terminal-Ready line active */
		     | UART_MCR_OUT2	/* Set OUT2 - not always required, but when
					 * it is, it is ESSENTIAL for enabling interrupts
				 */
		     ,uart->base + UART_MCR);	/* Modem Control Register */
		break;
	case SNDRV_SERIAL_MS124W_SA:
	case SNDRV_SERIAL_MS124W_MB:
		/* MS-124W can draw power from RTS and DTR if they
		   are in opposite states. */ 
		outb(UART_MCR_RTS | (0&UART_MCR_DTR) | UART_MCR_OUT2,
		     uart->base + UART_MCR);
		break;
	case SNDRV_SERIAL_MS124T:
		/* MS-124T can draw power from RTS and/or DTR (preferably
		   both) if they are both asserted. */
		outb(UART_MCR_RTS | UART_MCR_DTR | UART_MCR_OUT2,
		     uart->base + UART_MCR);
		break;
	}

	if (uart->irq < 0) {
		byte = (0 & UART_IER_RDI)	/* Disable Receiver data interrupt */
		    |(0 & UART_IER_THRI)	/* Disable Transmitter holding register empty interrupt */
		    ;
	} else if (uart->adaptor == SNDRV_SERIAL_MS124W_SA) {
		byte = UART_IER_RDI	/* Enable Receiver data interrupt */
		    | UART_IER_MSI	/* Enable Modem status interrupt */
		    ;
	} else if (uart->adaptor == SNDRV_SERIAL_GENERIC) {
		byte = UART_IER_RDI	/* Enable Receiver data interrupt */
		    | UART_IER_MSI	/* Enable Modem status interrupt */
		    | UART_IER_THRI	/* Enable Transmitter holding register empty interrupt */
		    ;
	} else {
		byte = UART_IER_RDI	/* Enable Receiver data interrupt */
		    | UART_IER_THRI	/* Enable Transmitter holding register empty interrupt */
		    ;
	}
	outb(byte, uart->base + UART_IER);	/* Interrupt enable Register */

	inb(uart->base + UART_LSR);	/* Clear any pre-existing overrun indication */
	inb(uart->base + UART_IIR);	/* Clear any pre-existing transmit interrupt */
	inb(uart->base + UART_RX);	/* Clear any pre-existing receive interrupt */
}

static void snd_uart16550_do_close(struct snd_uart16550 * uart)
{
	if (uart->irq < 0)
		snd_uart16550_del_timer(uart);

	/* NOTE: may need to disable interrupts before de-registering out handler.
	 * For now, the consequences are harmless.
	 */

	outb((0 & UART_IER_RDI)		/* Disable Receiver data interrupt */
	     |(0 & UART_IER_THRI)	/* Disable Transmitter holding register empty interrupt */
	     ,uart->base + UART_IER);	/* Interrupt enable Register */

	switch (uart->adaptor) {
	default:
		outb((0 & UART_MCR_RTS)		/* Deactivate Request-To-Send line  */
		     |(0 & UART_MCR_DTR)	/* Deactivate Data-Terminal-Ready line */
		     |(0 & UART_MCR_OUT2)	/* Deactivate OUT2 */
		     ,uart->base + UART_MCR);	/* Modem Control Register */
	  break;
	case SNDRV_SERIAL_MS124W_SA:
	case SNDRV_SERIAL_MS124W_MB:
		/* MS-124W can draw power from RTS and DTR if they
		   are in opposite states; leave it powered. */ 
		outb(UART_MCR_RTS | (0&UART_MCR_DTR) | (0&UART_MCR_OUT2),
		     uart->base + UART_MCR);
		break;
	case SNDRV_SERIAL_MS124T:
		/* MS-124T can draw power from RTS and/or DTR (preferably
		   both) if they are both asserted; leave it powered. */
		outb(UART_MCR_RTS | UART_MCR_DTR | (0&UART_MCR_OUT2),
		     uart->base + UART_MCR);
		break;
	}

	inb(uart->base + UART_IIR);	/* Clear any outstanding interrupts */

	/* Restore old divisor */
	if (uart->divisor != 0) {
		outb(UART_LCR_DLAB		/* Divisor latch access bit */
		     ,uart->base + UART_LCR);	/* Line Control Register */
		outb(uart->old_divisor_lsb
		     ,uart->base + UART_DLL);	/* Divisor Latch Low */
		outb(uart->old_divisor_msb
		     ,uart->base + UART_DLM);	/* Divisor Latch High */
		/* Restore old LCR (data bits, stop bits, parity, DLAB) */
		outb(uart->old_line_ctrl_reg
		     ,uart->base + UART_LCR);	/* Line Control Register */
	}
}

static int snd_uart16550_input_open(struct snd_rawmidi_substream *substream)
{
	unsigned long flags;
	struct snd_uart16550 *uart = substream->rmidi->private_data;

	spin_lock_irqsave(&uart->open_lock, flags);
	if (uart->filemode == SERIAL_MODE_NOT_OPENED)
		snd_uart16550_do_open(uart);
	uart->filemode |= SERIAL_MODE_INPUT_OPEN;
	uart->midi_input[substream->number] = substream;
	spin_unlock_irqrestore(&uart->open_lock, flags);
	return 0;
}

static int snd_uart16550_input_close(struct snd_rawmidi_substream *substream)
{
	unsigned long flags;
	struct snd_uart16550 *uart = substream->rmidi->private_data;

	spin_lock_irqsave(&uart->open_lock, flags);
	uart->filemode &= ~SERIAL_MODE_INPUT_OPEN;
	uart->midi_input[substream->number] = NULL;
	if (uart->filemode == SERIAL_MODE_NOT_OPENED)
		snd_uart16550_do_close(uart);
	spin_unlock_irqrestore(&uart->open_lock, flags);
	return 0;
}

static void snd_uart16550_input_trigger(struct snd_rawmidi_substream *substream,
					int up)
{
	unsigned long flags;
	struct snd_uart16550 *uart = substream->rmidi->private_data;

	spin_lock_irqsave(&uart->open_lock, flags);
	if (up)
		uart->filemode |= SERIAL_MODE_INPUT_TRIGGERED;
	else
		uart->filemode &= ~SERIAL_MODE_INPUT_TRIGGERED;
	spin_unlock_irqrestore(&uart->open_lock, flags);
}

static int snd_uart16550_output_open(struct snd_rawmidi_substream *substream)
{
	unsigned long flags;
	struct snd_uart16550 *uart = substream->rmidi->private_data;

	spin_lock_irqsave(&uart->open_lock, flags);
	if (uart->filemode == SERIAL_MODE_NOT_OPENED)
		snd_uart16550_do_open(uart);
	uart->filemode |= SERIAL_MODE_OUTPUT_OPEN;
	uart->midi_output[substream->number] = substream;
	spin_unlock_irqrestore(&uart->open_lock, flags);
	return 0;
};

static int snd_uart16550_output_close(struct snd_rawmidi_substream *substream)
{
	unsigned long flags;
	struct snd_uart16550 *uart = substream->rmidi->private_data;

	spin_lock_irqsave(&uart->open_lock, flags);
	uart->filemode &= ~SERIAL_MODE_OUTPUT_OPEN;
	uart->midi_output[substream->number] = NULL;
	if (uart->filemode == SERIAL_MODE_NOT_OPENED)
		snd_uart16550_do_close(uart);
	spin_unlock_irqrestore(&uart->open_lock, flags);
	return 0;
};

static inline int snd_uart16550_buffer_can_write(struct snd_uart16550 *uart,
						 int Num)
{
	if (uart->buff_in_count + Num < TX_BUFF_SIZE)
		return 1;
	else
		return 0;
}

static inline int snd_uart16550_write_buffer(struct snd_uart16550 *uart,
					     unsigned char byte)
{
	unsigned short buff_in = uart->buff_in;
	if (uart->buff_in_count < TX_BUFF_SIZE) {
		uart->tx_buff[buff_in] = byte;
		buff_in++;
		buff_in &= TX_BUFF_MASK;
		uart->buff_in = buff_in;
		uart->buff_in_count++;
		if (uart->irq < 0) /* polling mode */
			snd_uart16550_add_timer(uart);
		return 1;
	} else
		return 0;
}

static int snd_uart16550_output_byte(struct snd_uart16550 *uart,
				     struct snd_rawmidi_substream *substream,
				     unsigned char midi_byte)
{
	if (uart->buff_in_count == 0                    /* Buffer empty? */
	    && ((uart->adaptor != SNDRV_SERIAL_MS124W_SA &&
	    uart->adaptor != SNDRV_SERIAL_GENERIC) ||
		(uart->fifo_count == 0                  /* FIFO empty? */
		 && (inb(uart->base + UART_MSR) & UART_MSR_CTS)))) { /* CTS? */

	        /* Tx Buffer Empty - try to write immediately */
		if ((inb(uart->base + UART_LSR) & UART_LSR_THRE) != 0) {
		        /* Transmitter holding register (and Tx FIFO) empty */
		        uart->fifo_count = 1;
			outb(midi_byte, uart->base + UART_TX);
		} else {
		        if (uart->fifo_count < uart->fifo_limit) {
			        uart->fifo_count++;
				outb(midi_byte, uart->base + UART_TX);
			} else {
			        /* Cannot write (buffer empty) -
				 * put char in buffer */
				snd_uart16550_write_buffer(uart, midi_byte);
			}
		}
	} else {
		if (!snd_uart16550_write_buffer(uart, midi_byte)) {
			snd_printk(KERN_WARNING
				   "%s: Buffer overrun on device at 0x%lx\n",
				   uart->rmidi->name, uart->base);
			return 0;
		}
	}

	return 1;
}

static void snd_uart16550_output_write(struct snd_rawmidi_substream *substream)
{
	unsigned long flags;
	unsigned char midi_byte, addr_byte;
	struct snd_uart16550 *uart = substream->rmidi->private_data;
	char first;
	static unsigned long lasttime = 0;
	
	/* Interrupts are disabled during the updating of the tx_buff,
	 * since it is 'bad' to have two processes updating the same
	 * variables (ie buff_in & buff_out)
	 */

	spin_lock_irqsave(&uart->open_lock, flags);

	if (uart->irq < 0)	/* polling */
		snd_uart16550_io_loop(uart);

	if (uart->adaptor == SNDRV_SERIAL_MS124W_MB) {
		while (1) {
			/* buffer full? */
			/* in this mode we need two bytes of space */
			if (uart->buff_in_count > TX_BUFF_SIZE - 2)
				break;
			if (snd_rawmidi_transmit(substream, &midi_byte, 1) != 1)
				break;
#ifdef SNDRV_SERIAL_MS124W_MB_NOCOMBO
			/* select exactly one of the four ports */
			addr_byte = (1 << (substream->number + 4)) | 0x08;
#else
			/* select any combination of the four ports */
			addr_byte = (substream->number << 4) | 0x08;
			/* ...except none */
			if (addr_byte == 0x08)
				addr_byte = 0xf8;
#endif
			snd_uart16550_output_byte(uart, substream, addr_byte);
			/* send midi byte */
			snd_uart16550_output_byte(uart, substream, midi_byte);
		}
	} else {
		first = 0;
		while (snd_rawmidi_transmit_peek(substream, &midi_byte, 1) == 1) {
			/* Also send F5 after 3 seconds with no data
			 * to handle device disconnect */
			if (first == 0 &&
			    (uart->adaptor == SNDRV_SERIAL_SOUNDCANVAS ||
			     uart->adaptor == SNDRV_SERIAL_GENERIC) &&
			    (uart->prev_out != substream->number ||
			     time_after(jiffies, lasttime + 3*HZ))) {

				if (snd_uart16550_buffer_can_write(uart, 3)) {
					/* Roland Soundcanvas part selection */
					/* If this substream of the data is
					 * different previous substream
					 * in this uart, send the change part
					 * event
					 */
					uart->prev_out = substream->number;
					/* change part */
					snd_uart16550_output_byte(uart, substream,
								  0xf5);
					/* data */
					snd_uart16550_output_byte(uart, substream,
								  uart->prev_out + 1);
					/* If midi_byte is a data byte,
					 * send the previous status byte */
					if (midi_byte < 0x80 &&
					    uart->adaptor == SNDRV_SERIAL_SOUNDCANVAS)
						snd_uart16550_output_byte(uart, substream, uart->prev_status[uart->prev_out]);
				} else if (!uart->drop_on_full)
					break;

			}

			/* send midi byte */
			if (!snd_uart16550_output_byte(uart, substream, midi_byte) &&
			    !uart->drop_on_full )
				break;

			if (midi_byte >= 0x80 && midi_byte < 0xf0)
				uart->prev_status[uart->prev_out] = midi_byte;
			first = 1;

			snd_rawmidi_transmit_ack( substream, 1 );
		}
		lasttime = jiffies;
	}
	spin_unlock_irqrestore(&uart->open_lock, flags);
}

static void snd_uart16550_output_trigger(struct snd_rawmidi_substream *substream,
					 int up)
{
	unsigned long flags;
	struct snd_uart16550 *uart = substream->rmidi->private_data;

	spin_lock_irqsave(&uart->open_lock, flags);
	if (up)
		uart->filemode |= SERIAL_MODE_OUTPUT_TRIGGERED;
	else
		uart->filemode &= ~SERIAL_MODE_OUTPUT_TRIGGERED;
	spin_unlock_irqrestore(&uart->open_lock, flags);
	if (up)
		snd_uart16550_output_write(substream);
}

static struct snd_rawmidi_ops snd_uart16550_output =
{
	.open =		snd_uart16550_output_open,
	.close =	snd_uart16550_output_close,
	.trigger =	snd_uart16550_output_trigger,
};

static struct snd_rawmidi_ops snd_uart16550_input =
{
	.open =		snd_uart16550_input_open,
	.close =	snd_uart16550_input_close,
	.trigger =	snd_uart16550_input_trigger,
};

static int snd_uart16550_free(struct snd_uart16550 *uart)
{
	if (uart->irq >= 0)
		free_irq(uart->irq, uart);
	release_and_free_resource(uart->res_base);
	kfree(uart);
	return 0;
};

static int snd_uart16550_dev_free(struct snd_device *device)
{
	struct snd_uart16550 *uart = device->device_data;
	return snd_uart16550_free(uart);
}

static int snd_uart16550_create(struct snd_card *card,
				unsigned long iobase,
				int irq,
				unsigned int speed,
				unsigned int base,
				int adaptor,
				int droponfull,
				struct snd_uart16550 **ruart)
{
	static struct snd_device_ops ops = {
		.dev_free =	snd_uart16550_dev_free,
	};
	struct snd_uart16550 *uart;
	int err;


	if ((uart = kzalloc(sizeof(*uart), GFP_KERNEL)) == NULL)
		return -ENOMEM;
	uart->adaptor = adaptor;
	uart->card = card;
	spin_lock_init(&uart->open_lock);
	uart->irq = -1;
	uart->base = iobase;
	uart->drop_on_full = droponfull;

	if ((err = snd_uart16550_detect(uart)) <= 0) {
		printk(KERN_ERR "no UART detected at 0x%lx\n", iobase);
		snd_uart16550_free(uart);
		return -ENODEV;
	}

	if (irq >= 0 && irq != SNDRV_AUTO_IRQ) {
		if (request_irq(irq, snd_uart16550_interrupt,
				0, "Serial MIDI", uart)) {
			snd_printk(KERN_WARNING
				   "irq %d busy. Using Polling.\n", irq);
		} else {
			uart->irq = irq;
		}
	}
	uart->divisor = base / speed;
	uart->speed = base / (unsigned int)uart->divisor;
	uart->speed_base = base;
	uart->prev_out = -1;
	uart->prev_in = 0;
	uart->rstatus = 0;
	memset(uart->prev_status, 0x80, sizeof(unsigned char) * SNDRV_SERIAL_MAX_OUTS);
	init_timer(&uart->buffer_timer);
	uart->buffer_timer.function = snd_uart16550_buffer_timer;
	uart->buffer_timer.data = (unsigned long)uart;
	uart->timer_running = 0;

	/* Register device */
	if ((err = snd_device_new(card, SNDRV_DEV_LOWLEVEL, uart, &ops)) < 0) {
		snd_uart16550_free(uart);
		return err;
	}

	switch (uart->adaptor) {
	case SNDRV_SERIAL_MS124W_SA:
	case SNDRV_SERIAL_MS124W_MB:
		/* MS-124W can draw power from RTS and DTR if they
		   are in opposite states. */ 
		outb(UART_MCR_RTS | (0&UART_MCR_DTR), uart->base + UART_MCR);
		break;
	case SNDRV_SERIAL_MS124T:
		/* MS-124T can draw power from RTS and/or DTR (preferably
		   both) if they are asserted. */
		outb(UART_MCR_RTS | UART_MCR_DTR, uart->base + UART_MCR);
		break;
	default:
		break;
	}

	if (ruart)
		*ruart = uart;

	return 0;
}

static void snd_uart16550_substreams(struct snd_rawmidi_str *stream)
{
	struct snd_rawmidi_substream *substream;

	list_for_each_entry(substream, &stream->substreams, list) {
		sprintf(substream->name, "Serial MIDI %d", substream->number + 1);
	}
}

static int snd_uart16550_rmidi(struct snd_uart16550 *uart, int device,
			       int outs, int ins,
			       struct snd_rawmidi **rmidi)
{
	struct snd_rawmidi *rrawmidi;
	int err;

	err = snd_rawmidi_new(uart->card, "UART Serial MIDI", device,
			      outs, ins, &rrawmidi);
	if (err < 0)
		return err;
	snd_rawmidi_set_ops(rrawmidi, SNDRV_RAWMIDI_STREAM_INPUT,
			    &snd_uart16550_input);
	snd_rawmidi_set_ops(rrawmidi, SNDRV_RAWMIDI_STREAM_OUTPUT,
			    &snd_uart16550_output);
	strcpy(rrawmidi->name, "Serial MIDI");
	snd_uart16550_substreams(&rrawmidi->streams[SNDRV_RAWMIDI_STREAM_OUTPUT]);
	snd_uart16550_substreams(&rrawmidi->streams[SNDRV_RAWMIDI_STREAM_INPUT]);
	rrawmidi->info_flags = SNDRV_RAWMIDI_INFO_OUTPUT |
			       SNDRV_RAWMIDI_INFO_INPUT |
			       SNDRV_RAWMIDI_INFO_DUPLEX;
	rrawmidi->private_data = uart;
	if (rmidi)
		*rmidi = rrawmidi;
	return 0;
}

static int snd_serial_probe(struct platform_device *devptr)
{
	struct snd_card *card;
	struct snd_uart16550 *uart;
	int err;
	int dev = devptr->id;

	switch (adaptor[dev]) {
	case SNDRV_SERIAL_SOUNDCANVAS:
		ins[dev] = 1;
		break;
	case SNDRV_SERIAL_MS124T:
	case SNDRV_SERIAL_MS124W_SA:
		outs[dev] = 1;
		ins[dev] = 1;
		break;
	case SNDRV_SERIAL_MS124W_MB:
		outs[dev] = 16;
		ins[dev] = 1;
		break;
	case SNDRV_SERIAL_GENERIC:
		break;
	default:
		snd_printk(KERN_ERR
			   "Adaptor type is out of range 0-%d (%d)\n",
			   SNDRV_SERIAL_MAX_ADAPTOR, adaptor[dev]);
		return -ENODEV;
	}

	if (outs[dev] < 1 || outs[dev] > SNDRV_SERIAL_MAX_OUTS) {
		snd_printk(KERN_ERR
			   "Count of outputs is out of range 1-%d (%d)\n",
			   SNDRV_SERIAL_MAX_OUTS, outs[dev]);
		return -ENODEV;
	}

	if (ins[dev] < 1 || ins[dev] > SNDRV_SERIAL_MAX_INS) {
		snd_printk(KERN_ERR
			   "Count of inputs is out of range 1-%d (%d)\n",
			   SNDRV_SERIAL_MAX_INS, ins[dev]);
		return -ENODEV;
	}

	err  = snd_card_create(index[dev], id[dev], THIS_MODULE, 0, &card);
	if (err < 0)
		return err;

	strcpy(card->driver, "Serial");
	strcpy(card->shortname, "Serial MIDI (UART16550A)");

	if ((err = snd_uart16550_create(card,
					port[dev],
					irq[dev],
					speed[dev],
					base[dev],
					adaptor[dev],
					droponfull[dev],
					&uart)) < 0)
		goto _err;

	err = snd_uart16550_rmidi(uart, 0, outs[dev], ins[dev], &uart->rmidi);
	if (err < 0)
		goto _err;

	sprintf(card->longname, "%s [%s] at %#lx, irq %d",
		card->shortname,
		adaptor_names[uart->adaptor],
		uart->base,
		uart->irq);

	snd_card_set_dev(card, &devptr->dev);

	if ((err = snd_card_register(card)) < 0)
		goto _err;

	platform_set_drvdata(devptr, card);
	return 0;

 _err:
	snd_card_free(card);
	return err;
}

static int snd_serial_remove(struct platform_device *devptr)
{
	snd_card_free(platform_get_drvdata(devptr));
	return 0;
}

#define SND_SERIAL_DRIVER	"snd_serial_u16550"

static struct platform_driver snd_serial_driver = {
	.probe		= snd_serial_probe,
	.remove		=  snd_serial_remove,
	.driver		= {
		.name	= SND_SERIAL_DRIVER,
		.owner	= THIS_MODULE,
	},
};

static void snd_serial_unregister_all(void)
{
	int i;

	for (i = 0; i < ARRAY_SIZE(devices); ++i)
		platform_device_unregister(devices[i]);
	platform_driver_unregister(&snd_serial_driver);
}

static int __init alsa_card_serial_init(void)
{
	int i, cards, err;

	if ((err = platform_driver_register(&snd_serial_driver)) < 0)
		return err;

	cards = 0;
	for (i = 0; i < SNDRV_CARDS; i++) {
		struct platform_device *device;
		if (! enable[i])
			continue;
		device = platform_device_register_simple(SND_SERIAL_DRIVER,
							 i, NULL, 0);
		if (IS_ERR(device))
			continue;
		if (!platform_get_drvdata(device)) {
			platform_device_unregister(device);
			continue;
		}
		devices[i] = device;
		cards++;
	}
	if (! cards) {
#ifdef MODULE
		printk(KERN_ERR "serial midi soundcard not found or device busy\n");
#endif
		snd_serial_unregister_all();
		return -ENODEV;
	}
	return 0;
}

static void __exit alsa_card_serial_exit(void)
{
	snd_serial_unregister_all();
}

module_init(alsa_card_serial_init)
module_exit(alsa_card_serial_exit)