On Fri, Jul 30, 2021 at 05:07:00AM -0700, Tom Rix wrote: > > On 7/29/21 6:48 PM, Xu Yilun wrote: > > On Thu, Jul 29, 2021 at 12:16:47PM -0700, Tom Rix wrote: > > > On 7/29/21 11:51 AM, Moritz Fischer wrote: > > > > 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? > > > My gripe is > > > > > > For a nominally common interface, compat_id has a vendor specific output. > > > > > > If for example another vendor wanted to use this field but their natural > > > format was an OF string. > > > > > > 16 bytes of raw hex would not work for them, so they would roll their own. > > > > > > which defeats the purpose of a common interface. > > > > > > > > > The language in the docs as-is is vague on the output format. > > > > > > DFL is the only user of the interface. > > > > > > So ver 2 > > > > > > https://lore.kernel.org/linux-fpga/4ab7dd2d-c215-6333-6860-6f7d0ac64c3d@xxxxxxxxxx/ > > > > > > Keeps the output as-is for dfl, so nothing breaks in userspace > > > > > > And adds flexibility for vendors to output their appropriate natural form. > > > > > > So compat_id becomes generally useful. > > Mixing types seems be strongly against in Documentation/filesystems/sysfs.rst. > > So in my opinion there should be a determined format for the output. The > > concern for this patch is which one is a better format, uuid style or > > 128 bit raw hex? > > > > And I vote for 128 bit raw hex, as other vendors may not use uuid_t as > > the identifier, may be an OF string. So we don't have to force them > > decorate it as the uuid style. > > So you would be ok with v2 of this patchset ? No. I prefer we keep the current implementation. I mean 128 bit raw hex could be a more compatible output format for all vendors, uuid style, string style or others. Thanks, Yilun > > Tom > > > > > Thanks > > Yilun > > > > > > > > Tom > > > > > > > > > > - Moritz > > > >
