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Commit 8633328b authored by Alex Williamson's avatar Alex Williamson Committed by Jesse Barnes
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PCI: Allow read/write access to sysfs I/O port resources 



PCI sysfs resource files currently only allow mmap'ing.  On x86 this
works fine for memory backed BARs, but doesn't work at all for I/O
port backed BARs.  Add read/write to I/O port PCI sysfs resource
files to allow userspace access to these device regions.

Acked-by: default avatarChris Wright <chrisw@redhat.com>
Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
Signed-off-by: default avatarJesse Barnes <jbarnes@virtuousgeek.org>
parent 2491762c

Documentation/filesystems/sysfs-pci.txt

+5 −2
Original line number Diff line number Diff line
@@ -39,7 +39,7 @@ files, each with their own function. 
       local_cpus	   nearby CPU mask (cpumask, ro)

       remove		   remove device from kernel's list (ascii, wo)

       resource		   PCI resource host addresses (ascii, ro)

       resource0..N	   PCI resource N, if present (binary, mmap)

       resource0..N	   PCI resource N, if present (binary, mmap, rw[1])

       resource0_wc..N_wc  PCI WC map resource N, if prefetchable (binary, mmap)

       rom		   PCI ROM resource, if present (binary, ro)

       subsystem_device	   PCI subsystem device (ascii, ro)
@@ -54,13 +54,16 @@ files, each with their own function. 
  binary - file contains binary data

  cpumask - file contains a cpumask type



[1] rw for RESOURCE_IO (I/O port) regions only



The read only files are informational, writes to them will be ignored, with

the exception of the 'rom' file.  Writable files can be used to perform

actions on the device (e.g. changing config space, detaching a device).

mmapable files are available via an mmap of the file at offset 0 and can be

used to do actual device programming from userspace.  Note that some platforms

don't support mmapping of certain resources, so be sure to check the return

value from any attempted mmap.

value from any attempted mmap.  The most notable of these are I/O port

resources, which also provide read/write access.



The 'enable' file provides a counter that indicates how many times the device 

has been enabled.  If the 'enable' file currently returns '4', and a '1' is

drivers/pci/pci-sysfs.c

+68 −0
Original line number Diff line number Diff line
@@ -778,6 +778,70 @@ pci_mmap_resource_wc(struct file *filp, struct kobject *kobj, 
	return pci_mmap_resource(kobj, attr, vma, 1);

}



static ssize_t

pci_resource_io(struct file *filp, struct kobject *kobj,

		struct bin_attribute *attr, char *buf,

		loff_t off, size_t count, bool write)

{

	struct pci_dev *pdev = to_pci_dev(container_of(kobj,

						       struct device, kobj));

	struct resource *res = attr->private;

	unsigned long port = off;

	int i;



	for (i = 0; i < PCI_ROM_RESOURCE; i++)

		if (res == &pdev->resource[i])

			break;

	if (i >= PCI_ROM_RESOURCE)

		return -ENODEV;



	port += pci_resource_start(pdev, i);



	if (port > pci_resource_end(pdev, i))

		return 0;



	if (port + count - 1 > pci_resource_end(pdev, i))

		return -EINVAL;



	switch (count) {

	case 1:

		if (write)

			outb(*(u8 *)buf, port);

		else

			*(u8 *)buf = inb(port);

		return 1;

	case 2:

		if (write)

			outw(*(u16 *)buf, port);

		else

			*(u16 *)buf = inw(port);

		return 2;

	case 4:

		if (write)

			outl(*(u32 *)buf, port);

		else

			*(u32 *)buf = inl(port);

		return 4;

	}

	return -EINVAL;

}



static ssize_t

pci_read_resource_io(struct file *filp, struct kobject *kobj,

		     struct bin_attribute *attr, char *buf,

		     loff_t off, size_t count)

{

	return pci_resource_io(filp, kobj, attr, buf, off, count, false);

}



static ssize_t

pci_write_resource_io(struct file *filp, struct kobject *kobj,

		      struct bin_attribute *attr, char *buf,

		      loff_t off, size_t count)

{

	return pci_resource_io(filp, kobj, attr, buf, off, count, true);

}



/**

 * pci_remove_resource_files - cleanup resource files

 * @pdev: dev to cleanup
@@ -828,6 +892,10 @@ static int pci_create_attr(struct pci_dev *pdev, int num, int write_combine) 
			sprintf(res_attr_name, "resource%d", num);

			res_attr->mmap = pci_mmap_resource_uc;

		}

		if (pci_resource_flags(pdev, num) & IORESOURCE_IO) {

			res_attr->read = pci_read_resource_io;

			res_attr->write = pci_write_resource_io;

		}

		res_attr->attr.name = res_attr_name;

		res_attr->attr.mode = S_IRUSR | S_IWUSR;

		res_attr->size = pci_resource_len(pdev, num);