path: root/Documentation
diff options
authorTimothy S. Nelson <wayland@wayland.id.au>2009-01-30 06:12:47 +1100
committerJesse Barnes <jbarnes@virtuousgeek.org>2009-02-04 16:58:41 -0800
commit97c44836cdec1ea713a15d84098a1a908157e68f (patch)
treebc544c64ed8eeb3feb2f0b210ae7db04a40e1bae /Documentation
parent3419c75e15f82c3ab09bd944fddbde72c9e4b3ea (diff)
PCI: return error on failure to read PCI ROMs
This patch makes the ROM reading code return an error to user space if the size of the ROM read is equal to 0. The patch also emits a warnings if the contents of the ROM are invalid, and documents the effects of the "enable" file on ROM reading. Signed-off-by: Timothy S. Nelson <wayland@wayland.id.au> Acked-by: Alex Villacis-Lasso <a_villacis@palosanto.com> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Diffstat (limited to 'Documentation')
1 files changed, 12 insertions, 1 deletions
diff --git a/Documentation/filesystems/sysfs-pci.txt b/Documentation/filesystems/sysfs-pci.txt
index 68ef48839c0..9f8740ca3f3 100644
--- a/Documentation/filesystems/sysfs-pci.txt
+++ b/Documentation/filesystems/sysfs-pci.txt
@@ -9,6 +9,7 @@ that support it. For example, a given bus might look like this:
| |-- class
| |-- config
| |-- device
+ | |-- enable
| |-- irq
| |-- local_cpus
| |-- resource
@@ -32,6 +33,7 @@ files, each with their own function.
class PCI class (ascii, ro)
config PCI config space (binary, rw)
device PCI device (ascii, ro)
+ enable Whether the device is enabled (ascii, rw)
irq IRQ number (ascii, ro)
local_cpus nearby CPU mask (cpumask, ro)
resource PCI resource host addresses (ascii, ro)
@@ -57,10 +59,19 @@ 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 '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
+echoed into it, it will then return '5'. Echoing a '0' into it will decrease
+the count. Even when it returns to 0, though, some of the initialisation
+may not be reversed.
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.
+call, and disable it following the access by writing "0" to the file. Note
+that the device must be enabled for a rom read to return data succesfully.
+In the event a driver is not bound to the device, it can be enabled using the
+'enable' file, documented above.
Accessing legacy resources through sysfs