On Wed, Jul 28, 2021 at 01:36:56AM +0000, Wu, Hao wrote: > > On 7/26/21 3:12 PM, Russ Weight wrote: > > > On 7/26/21 1:26 PM, trix@xxxxxxxxxx wrote: > > >> From: Tom Rix <trix@xxxxxxxxxx> > > >> > > >> An fpga region's compat_id is exported by the sysfs > > >> as a 128 bit hex string formed by concatenating two > > >> 64 bit values together. > > >> > > >> The only user of compat_id is dfl. Its user library > > >> opae converts this value into a uuid. > > >> > > >> ex/ > > >> $ cat /sys/class/fpga_region/region1/compat_id > > >> f3c9941350814aadbced07eb84a6d0bb > > >> > > >> Is reported as > > >> $ fpgainfo bmc > > >> ... > > >> Pr Interface Id : f3c99413-5081-4aad-bced-07eb84a6d0bb > > >> > > >> Storing a uuid as 2 64 bit values is vendor specific. > > >> And concatenating them together is vendor specific. > > >> > > >> It is better to store and print out as a vendor neutral uuid. > > >> > > >> Change fpga_compat_id from a struct to a union. > > >> Keep the old 64 bit values for dfl. > > >> Sysfs output is now > > >> f3c99413-5081-4aad-bced-07eb84a6d0bb > > > I'm fowarding feedback from Tim Whisonant, one of the OPAE userspace > > > developers: > > > > > > I think that this change to the sysfs for the compat_id node will > > > end up breaking the SDK, which does not expect the '-' characters to > > > be included when parsing the sysfs value. Currently, it is parsed as > > > a raw hex string without regard to any '-' characters. This goes for > > > any "guid" currently exported by sysfs and for what we read in the > > > device MMIO space. > > > > Yes, it will. > > > > And there are other places, like dfl-afu-main.c:afu_id_show() > > > > outputs raw hex that sdk turns into a uuid. > > > > > > Some options. > > > > If no one but dfl will ever use it, then v1 of patchset. > > > > If others can use it but don't want to change dfl, then v2 of patchset, > > my favorite. > > > > Or this one for uuid for everyone, what have been v3 but changed too much. > > > > > > could dfl change generally to output uuid's to the sysfs ? > > > > this would be generally helpful and a one time disruption to the sdk. > > This change limited the output format to uuid_t, but if any hardware doesn't > use uuid_t on hardware may have to convert it back from the sysfs output in > userspace. Leave it to print hardware values (e.g. from register), and convert > it in userspace should be fine too I think. I'm not entirely sure. I seem to recall there being examples of sysfs files returning different things for different drivers. That being said it seems largely cosmetic to add the '-' in between. If it breaks userspace, I'm against it. If you *need* it make a compat_uuid entry or something in that case? - Moritz
