From jesse.barnes@intel.com Fri Dec 9 14:06:51 2005 From: Jesse Barnes To: gregkh@suse.de, linux-kernel@vger.kernel.org, Ian Romanick Subject: PCI: document sysfs rom file interface Date: Fri, 9 Dec 2005 11:55:03 -0800 Message-Id: <200512091155.03552.jesse.barnes@intel.com> idr gently pointed out today that not only is the sysfs rom file interface somewhat unintuitive (despite my efforts and initial implementation), but it's also undocumented! This patch to Documentation/filesystems/sysfs-pci.txt corrects the latter problem; the former is a userland ABI now though, so we're stuck with it for awhile at least. Signed-off-by: Jesse Barnes Signed-off-by: Greg Kroah-Hartman --- Documentation/filesystems/sysfs-pci.txt | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-) --- gregkh-2.6.orig/Documentation/filesystems/sysfs-pci.txt +++ gregkh-2.6/Documentation/filesystems/sysfs-pci.txt @@ -1,4 +1,5 @@ Accessing PCI device resources through sysfs +-------------------------------------------- sysfs, usually mounted at /sys, provides access to PCI resources on platforms that support it. For example, a given bus might look like this: @@ -47,14 +48,21 @@ files, each with their own function. binary - file contains binary data cpumask - file contains a cpumask type -The read only files are informational, writes to them will be ignored. -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. +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. + +The 'rom' file is special in that it provides read-only access to the device's +ROM file, if available. It's disabled by default, however, so applications +should write the string "1" to the file to enable it before attempting a read +call, and disable it following the access by writing "0" to the file. Accessing legacy resources through sysfs +---------------------------------------- Legacy I/O port and ISA memory resources are also provided in sysfs if the underlying platform supports them. They're located in the PCI class heirarchy, @@ -75,6 +83,7 @@ simply dereference the returned pointer to access legacy memory space. Supporting PCI access on new platforms +-------------------------------------- In order to support PCI resource mapping as described above, Linux platform code must define HAVE_PCI_MMAP and provide a pci_mmap_page_range function.