incompatible pci sysfs change since 3.12 (5136b2da770d)

Hi.

I am an author of LinuxCNC, a GPL'd CNC control for Linux.

Recently we added support for userspace PCI drivers. This worked with kernel 3.2 but doesn't with kernel 3.16. The software fails early with

    Failed to open "/sys/devices/pci0000:00/.../enable" (Permission denied)

This appears to be because our software relies on the documented "enable" sysfs file for pci devices (Documentation/filesystem/sysfs-pci.txt) which was (unintentionally?) changed to "enabled" in the above-named patch:

5136b2da770d PCI: convert bus code to use dev_groups
...

(quoted diff) +1 -1

+static DEVICE_ATTR_RW(enabled);
...
-   __ATTR(enable, 0600, is_enabled_show, is_enabled_store),

Are we in the LinuxCNC project wrong in thinking that stuff in /sys (and not /sys/debug) is supposed to be a durable API/interface for userspace to the kernel? (It must be a low-usage API if it went unnoticed for a year :-/)

We'll have to work around it by modifying our software (since we'd like to work with the kernels people already have) in any case.

Even if it is not going to be changed compatibly with older kernels, it seems like the documentation should be updated!

Ugh, that's my fault, I made a typo and should not have renamed the sysfs file, very sorry about that.

I'll work on making up a patch to fix this and get it into the stable kernels so that you don't have to have a work-around for very long.

Quoted 5 lines · Greg Kroah-Hartman

Ugh, that's my fault, I made a typo and should not have renamed the sysfs file, very sorry about that.

I'll work on making up a patch to fix this and get it into the stable kernels so that you don't have to have a work-around for very long.

Thank you! I appreciate your quick response.

I've now sent a patch that should fix this. If you could verify it, I'd appreciate it.