On Sat, 2024-07-20 at 10:43 +0100, Jonathan Cameron wrote: > On Thu, 18 Jul 2024 16:32:33 +0200 > Nuno Sá <noname.nuno@xxxxxxxxx> wrote: > > > On Tue, 2024-07-16 at 19:14 +0100, Jonathan Cameron wrote: > > > On Tue, 9 Jul 2024 13:14:30 +0200 > > > Nuno Sa <nuno.sa@xxxxxxxxxx> wrote: > > > > > > > This adds a basic debugfs interface for backends. Two new ops are being > > > > added: > > > > > > > > * debugfs_reg_access: Analogous to the core IIO one but for backend > > > > devices. > > > > * debugfs_print_chan_status: One useful usecase for this one is for > > > > testing test tones in a digital interface and "ask" the backend to > > > > dump more details on why a test tone might have errors. > > > > > > > > Signed-off-by: Nuno Sa <nuno.sa@xxxxxxxxxx> > > > Debugfs deserved docs as well as sysfs. > > > Same place in Documentation/ABI/ > > > > > > Obviously we've neglected this in the past, but nice to do it right > > > nor new stuff. > > > > > > > I see. So you mean adding debugfs-iio? > > Probably debugfs-iio-backend for this stuff, though we should have > a more general doc as well. > > > > > There's one thing I'm not sure though... I'm contemplating the case where > > one device > > may have multiple backends in which case I'm doing: > > > > back->name = name; > > > > where name comes from FW (DT usually). That obviously means the interface > > won't be > > always consistent which I guess it's not a real problem for debugfs? > > > > How would the interface look in the file? Something like? > > > > /sys/kernel/debug/iio/iio:deviceX/<backend_name>_direct_reg_access > > That's fine - fairly common sort of thing to see in debugfs. > > > > > Or should we think in a more reliable naming? One option that came to mind > > is > > > > /sys/kernel/debug/iio/iio:deviceX/backendY_direct_reg_access > If you were doing this it might be better as a directory. > e.g. backendY/direct_reg_access > > > > where Y would be the corresponding index in io-backend-names. > > > > One thing not optimal with the above would be identifying the actual backend > > device. > > It would then maybe make sense having a 'backend_name' interface which I > > think is > > likely too much just for this? > It kind of depends on your expected usecase. These are in debugfs so there > is an assumption they aren't a 'normal operation' thing. So if they > are going to typically be poked by a user, then complex file names are fine. > If it's going to be scripted, then stable names something like > backendY/name > backendY/direct_reg_access etc > would be easier to use. > Yeah, I think the main usage (the one I do at least) is for the user to directly play and poke with this. However I don't think that the scripting usecase to be that crazy (or unlikely) and I do like stable things :). Also liked your suggestion about grouping the interfaces in a backendY directory. We'll likely need an iio_backend_info struct interface for backends to pass in when registering. Maybe too much for a debug interface but this kind of 'info' structure may very well be something we'll need in the future. Anyways, I think I'll give this a try for v2 so we can see how it looks like in practise. > I'm not bothered as much about consistency of this debug interface as I would > be about sysfs, so up to you (or other reviewers) for which you prefer. > Yeah, I was kind of expecting that (no one should blindly rely on debugFS) :) - Nuno Sá
