On Wed, Aug 10, 2022 at 08:54:36AM +0300, Krzysztof Kozlowski wrote: > On 09/08/2022 22:21, Bjorn Helgaas wrote: > > [+cc regressions list] > > > > 23d99baf9d72 appeared in v5.19-rc1. > > > > On Tue, Aug 09, 2022 at 11:29:43AM -0700, Stephen Hemminger wrote: > >> This commit broke the driver override script in DPDK. > >> This is an API/ABI breakage, please revert or fix the commit. > >> > >> Report of problem: > >> http://mails.dpdk.org/archives/dev/2022-August/247794.html > > Thanks for the report. I'll take a look. > > >> > >> > >> commit 23d99baf9d729ca30b2fb6798a7b403a37bfb800 > >> Author: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> > >> Date: Tue Apr 19 13:34:28 2022 +0200 > >> > >> PCI: Use driver_set_override() instead of open-coding > >> > >> Use a helper to set driver_override to the reduce amount of duplicated > >> code. Make the driver_override field const char, because it is not > >> modified by the core and it matches other subsystems. > >> > >> Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx> > >> Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > >> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> > >> Link: https://lore.kernel.org/r/20220419113435.246203-6-krzysztof.kozlowski@xxxxxxxxxx > >> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > >> > >> > >> The script is sending single nul character to remove override > >> and that no longer works. > > The sysfs API clearly states: > "and > may be cleared with an empty string (echo > driver_override)." > Documentation/ABI/testing/sysfs-bus-pci > > Sending other data and expecting the same result is not conforming to > API. Therefore we have usual example of some undocumented behavior which > user-space started relying on and instead using API, user-space expect > that undocumented behavior to be back. > > Yay! I wonder what is the point to even describe the ABI if user-space > can simply ignore it? One can argue that a string of just '\0' is an "empty string" and we should be able to properly handle this in the kernel. Heck, "\0\0\0\0\0\0" is also an "empty string", right? I don't have an issue with fixing the kernel up here, it should be able to handle this. thanks, greg k-h
