On Tue, Sep 16, 2014 at 02:27:15PM -0700, Darren Hart wrote: > On Tue, Sep 16, 2014 at 01:52:47PM -0700, Darren Hart wrote: > > On Tue, Sep 16, 2014 at 01:54:25PM +0200, Frans Klaver wrote: > > > On Mon, Sep 15, 2014 at 11:55 PM, Frans Klaver <franskla...@gmail.com> > > > wrote: > > > > On Mon, Sep 15, 2014 at 02:51:25PM -0700, Greg Kroah-Hartman wrote: > > > >> On Mon, Sep 15, 2014 at 02:49:02PM -0700, Darren Hart wrote: > > > >> > > > > >> > This patch is fine as is. However, Greg has supported propogating > > > >> > the error code > > > >> > through to the sysfs interface (if I understand him correctly on an > > > >> > earlier post > > > >> > to this list). This would require an addition change to this patch > > > >> > would > > > >> > propogated the get_cpufv error code in show_available_cpuv(), > > > >> > show_cpuv(), and > > > >> > store_cpuv(). As it is, we return -ENODEV on any failure, where an > > > >> > ACPI call > > > >> > error should probably return -ENXIO as I understand it. > > > >> > > > >> I really have no idea at this point in time what to recommend. How > > > >> about just stick with what is happening today so that: > > > >> > > > >> > However, there was a rather famous change in error code handling in > > > >> > which pulse > > > >> > audio broke and Linus was very upset with one of his maintainers. > > > >> > > > >> That doesn't happen :) > > > > > > > > So if I interpret that correctly, we're dropping the last patch > > > > (ENODEV -> ENXIO) from the series? That's fine by me. As mentioned > > > > earlier, I already saw something else break because I returned ENXIO > > > > instead of ENODEV. > > > > > > > > Maybe it's a good idea to try and document the expected behavior > > > > somewhere, if even Greg isn't sure what to do. > > > > > > For good measure: > > > > > > v2 will not change the return values at the sysfs interface, meaning > > > we will always return -ENODEV on error. I am going to try to keep as > > > much internal functions propagating errors as possible though, unless > > > someone strongly disagrees. > > > > > > Thanks, > > > Frans > > > > I cornered Linus today and asked about this specifically. The policy is > > this: > > > > Don't change the sysfs return codes without good reason. A good reason > > could be > > a real bug or problem with the return codes. It could also be to consolidate > > error handling which makes things more uniform, etc. > > > > If this results in broken userspace, the maintainer will revert the change. > > > > This is probably a good thing to add to sysfs-rules.txt. I'll prepare a > > patch. > > > > What do people think of appending this to sysfs-rules.txt? > > - When reading and writing sysfs device attribute files, avoid dependency > on specific error codes wherever possible. This minimizes coupling to > the error handling implemementation within the kernel. > > In general, failures to read or write sysfs device attributes shall > propogate errors wherever possible. Common errors include, but are not > limited to: > > -EIO: The read or store operation is not supported, typically returned by > the sysfs system itself if the read or store pointer is NULL. > > -ENXIO: The read or store operation failed > > Error codes will not be changed without good reason, and should a change > to error codes result in user-space breakage, it will be fixed, or the > the offending change will be reverted. > > Userspace applications can, however, expect the format and contents of > the attribute files to remain consistent in the absence of a version > attribute change in the context of a given attributes.
Looks reasonable, thanks. Care to turn it into a patch that I can apply? thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
