// SPDX-License-Identifier: GPL-2.0

  /*
   *	pci_syscall.c
   *
   * For architectures where we want to allow direct access
   * to the PCI config stuff - it would probably be preferable
   * on PCs too, but there people just do it by hand with the
   * magic northbridge registers..
   */

  #include <linux/errno.h>
  #include <linux/pci.h>

  #include <linux/syscalls.h>

  #include <linux/uaccess.h>

  #include "pci.h"

  SYSCALL_DEFINE5(pciconfig_read, unsigned long, bus, unsigned long, dfn,
  		unsigned long, off, unsigned long, len, void __user *, buf)

  {
  	struct pci_dev *dev;
  	u8 byte;
  	u16 word;
  	u32 dword;

  	long err;
  	long cfg_ret;

  	if (!capable(CAP_SYS_ADMIN))

  		return -EPERM;

  
  	err = -ENODEV;

  	dev = pci_get_bus_and_slot(bus, dfn);

  	if (!dev)
  		goto error;

  	switch (len) {
  	case 1:

  		cfg_ret = pci_user_read_config_byte(dev, off, &byte);

  		break;
  	case 2:

  		cfg_ret = pci_user_read_config_word(dev, off, &word);

  		break;
  	case 4:

  		cfg_ret = pci_user_read_config_dword(dev, off, &dword);

  		break;
  	default:
  		err = -EINVAL;

  		goto error;

  	}

  
  	err = -EIO;
  	if (cfg_ret != PCIBIOS_SUCCESSFUL)
  		goto error;
  
  	switch (len) {
  	case 1:
  		err = put_user(byte, (unsigned char __user *)buf);
  		break;
  	case 2:
  		err = put_user(word, (unsigned short __user *)buf);
  		break;
  	case 4:
  		err = put_user(dword, (unsigned int __user *)buf);
  		break;

  	}
  	pci_dev_put(dev);

  	return err;
  
  error:
  	/* ??? XFree86 doesn't even check the return value.  They
  	   just look for 0xffffffff in the output, since that's what
  	   they get instead of a machine check on x86.  */
  	switch (len) {
  	case 1:
  		put_user(-1, (unsigned char __user *)buf);
  		break;
  	case 2:
  		put_user(-1, (unsigned short __user *)buf);
  		break;
  	case 4:
  		put_user(-1, (unsigned int __user *)buf);
  		break;

  	}
  	pci_dev_put(dev);

  	return err;
  }

  SYSCALL_DEFINE5(pciconfig_write, unsigned long, bus, unsigned long, dfn,
  		unsigned long, off, unsigned long, len, void __user *, buf)

  {
  	struct pci_dev *dev;
  	u8 byte;
  	u16 word;
  	u32 dword;
  	int err = 0;
  
  	if (!capable(CAP_SYS_ADMIN))
  		return -EPERM;

  	dev = pci_get_bus_and_slot(bus, dfn);

  	if (!dev)
  		return -ENODEV;

  	switch (len) {

  	case 1:
  		err = get_user(byte, (u8 __user *)buf);
  		if (err)
  			break;

  		err = pci_user_write_config_byte(dev, off, byte);

  		if (err != PCIBIOS_SUCCESSFUL)
  			err = -EIO;
  		break;
  
  	case 2:
  		err = get_user(word, (u16 __user *)buf);
  		if (err)
  			break;

  		err = pci_user_write_config_word(dev, off, word);

  		if (err != PCIBIOS_SUCCESSFUL)
  			err = -EIO;
  		break;
  
  	case 4:
  		err = get_user(dword, (u32 __user *)buf);
  		if (err)
  			break;

  		err = pci_user_write_config_dword(dev, off, dword);

  		if (err != PCIBIOS_SUCCESSFUL)
  			err = -EIO;
  		break;
  
  	default:
  		err = -EINVAL;
  		break;

  	}

  	pci_dev_put(dev);

  	return err;
  }