From: Moritz Fischer <firstname.lastname@example.org> To: "Wu, Hao" <email@example.com> Cc: Tom Rix <firstname.lastname@example.org>, "Weight, Russell H" <email@example.com>, "firstname.lastname@example.org" <email@example.com>, "firstname.lastname@example.org" <email@example.com>, "firstname.lastname@example.org" <email@example.com> Subject: Re: [PATCH] fpga: region: handle compat_id as an uuid Date: Thu, 29 Jul 2021 11:51:23 -0700 [thread overview] Message-ID: <YQL4qyAmqj322HTz@epycbox.lan> (raw) In-Reply-To: <DM6PR11MB38199F872DC94971D9C8A53885EA9@DM6PR11MB3819.namprd11.prod.outlook.com> 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, firstname.lastname@example.org wrote: > > >> From: Tom Rix <email@example.com> > > >> > > >> 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
next prev parent reply other threads:[~2021-07-29 18:51 UTC|newest] Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-07-26 20:26 trix 2021-07-26 22:12 ` Russ Weight 2021-07-27 0:16 ` Tom Rix 2021-07-28 1:36 ` Wu, Hao 2021-07-29 18:51 ` Moritz Fischer [this message] 2021-07-29 19:16 ` Tom Rix 2021-07-30 1:48 ` Xu Yilun 2021-07-30 12:07 ` Tom Rix 2021-08-03 3:32 ` Xu Yilun 2021-08-03 12:21 ` Tom Rix 2021-08-04 1:44 ` Xu Yilun 2021-08-04 13:21 ` Tom Rix 2021-08-06 1:42 ` Xu Yilun 2021-07-26 23:35 ` kernel test robot
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