On Mon, Jan 29, 2024 at 12:26 AM Nuno Sá <noname.nuno@xxxxxxxxx> wrote: > > On Sat, 2024-01-27 at 15:15 +0000, Jonathan Cameron wrote: > > On Fri, 26 Jan 2024 15:26:08 +0100 > > Nuno Sá <noname.nuno@xxxxxxxxx> wrote: > > > > > On Fri, 2024-01-26 at 09:04 +0100, Nuno Sá wrote: > > > > On Thu, 2024-01-25 at 17:57 +0100, Rafael J. Wysocki wrote: > > > > > On Thu, Jan 25, 2024 at 4:31 PM Nuno Sá <noname.nuno@xxxxxxxxx> wrote: > > > > > > > > > > > > On Thu, 2024-01-25 at 09:14 +0100, Nuno Sá wrote: > > > > > > > > > > > > > > Hi Saravana, > > > > > > > > > > > > > > Thanks for your feedback, > > > > > > > > > > > > > > On Wed, 2024-01-24 at 19:21 -0800, Saravana Kannan wrote: > > > > > > > > On Tue, Jan 23, 2024 at 7:14 AM Nuno Sa via B4 Relay > > > > > > > > <devnull+nuno.sa.analog.com@xxxxxxxxxx> wrote: > > > > > > > > > > > > > > > > > > From: Nuno Sa <nuno.sa@xxxxxxxxxx> > > > > > > > > > > > > > > > > > > If a device_link is previously created (eg: via > > > > > > > > > fw_devlink_create_devlink()) before the supplier + consumer are > > > > > > > > > both > > > > > > > > > present and bound to their respective drivers, there's no way to > > > > > > > > > set > > > > > > > > > DL_FLAG_AUTOREMOVE_CONSUMER anymore while one can still set > > > > > > > > > DL_FLAG_AUTOREMOVE_SUPPLIER. Hence, rework the flags checks to > > > > > > > > > allow > > > > > > > > > for DL_FLAG_AUTOREMOVE_CONSUMER in the same way > > > > > > > > > DL_FLAG_AUTOREMOVE_SUPPLIER is done. > > > > > > > > > > > > > > > > Curious, why do you want to set DL_FLAG_AUTOREMOVE_CONSUMER? > > > > > > > > Especially if fw_devlink already created the link? You are > > > > > > > > effectively > > > > > > > > trying to delete the link fw_devlink created if any of your > > > > > > > > devices > > > > > > > > unbind. > > > > > > > > > > > > > > > > > > > > > > Well, this is still useful in the modules case as the link will be > > > > > > > relaxed > > > > > > > after > > > > > > > all devices are initialized and that will already clear > > > > > > > AUTOPROBE_CONSUMER > > > > > > > AFAIU. But, more importantly, if I'm not missing anything, in [1], > > > > > > > fw_devlinks > > > > > > > will be dropped after the consumer + supplier are bound which means > > > > > > > I > > > > > > > definitely > > > > > > > want to create a link between my consumer and supplier. > > > > > > > > > > > > > > > > > > > Ok, so to add a bit more on this, there are two cases: > > > > > > > > > > > > 1) Both sup and con are modules and after boot up, the link is relaxed > > > > > > and > > > > > > thus > > > > > > turned into a sync_state_only link. That means the link will be > > > > > > deleted > > > > > > anyways > > > > > > and AUTOPROBE_CONSUMER is already cleared by the time we try to change > > > > > > the > > > > > > link. > > > > > > > > > > > > 2) The built-in case where the link is kept as created by fw_devlink > > > > > > and > > > > > > this > > > > > > patch effectively clears AUTOPROBE_CONSUMER. > > > > > > > > > > > > Given the above, not sure what's the best option. I can think of 4: > > > > > > > > > > > > 1) Drop this patch and leave things as they are. > > > > > > DL_FLAG_AUTOREMOVE_CONSUMER > > > > > > is > > > > > > pretty much ignored in my call but it will turn the link in a MANAGED > > > > > > one > > > > > > and > > > > > > clear SYNC_STATE_ONLY. I could very well just pass 0 in the flags as > > > > > > DL_FLAG_AUTOREMOVE_CONSUMER is always ignored; > > > > > > > > > > > > 2) Rework this patch so we can still change an existing link to accept > > > > > > DL_FLAG_AUTOREMOVE_CONSUMER (in the modules case for example). > > > > > > > > > > > > However, instead of clearing AUTOPROBE_CONSUMER, I would add some > > > > > > checks > > > > > > so > > > > > > if > > > > > > flags have one of DL_FLAG_AUTOREMOVE_SUPPLIER or > > > > > > DL_FLAG_AUTOREMOVE_CONSUMER > > > > > > and > > > > > > AUTOPROBE_CONSUMER is already set, we ignore them. In fact, right now, > > > > > > I > > > > > > think > > > > > > one could pass DL_FLAG_AUTOREMOVE_SUPPLIER and link->flags ends ups > > > > > > with > > > > > > AUTOREMOVE_SUPPLIER | AUTOPROBE_CONSUMER which in theory is not > > > > > > allowed... > > > > > > > > > > No, because DL_FLAG_AUTOREMOVE_SUPPLIER is only added to the link > > > > > flags if DL_FLAG_AUTOREMOVE_CONSUMER is already set in there and the > > > > > former replaces the latter. > > > > > > > > > > > > > Oh yes, I missed that extra if() against the DL_FLAG_AUTOREMOVE_CONSUMER > > > > flag... > > > > > > > > > Now, DL_FLAG_AUTOREMOVE_CONSUMER cannot be set in the link flags if > > > > > AUTOPROBE_CONSUMER is set in there. > > > > > > > > > > > 3) Keep it as-is... This one is likely a NACK as I'm getting the > > > > > > feeling > > > > > > that > > > > > > clearing stuff that might have been created by fw_devlinks is probably > > > > > > a > > > > > > no- > > > > > > go. > > > > > > > > > > > > Let me know your thoughts... > > > > > > > > > > If the original creator of the link didn't indicate either > > > > > DL_FLAG_AUTOREMOVE_CONSUMER, or DL_FLAG_AUTOREMOVE_SUPPLIER, they are > > > > > expected to need the link to stay around until it is explicitly > > > > > deleted. > > > > > > > > > > Therefore adding any of these flags for an existing link where they > > > > > both are unset would be a mistake, because it would effectively cause > > > > > the link to live shorter than expected by the original creator and > > > > > that might lead to correctness issues. > > > > > > > > > > Thanks! > > > > > > > > Thanks Rafael, your last two paragraphs make it really clear what's the > > > > reasoning and why this patch is wrong. > > > > > > > > Jonathan, if nothing else comes that I need a re-spin, can you drop this > > > > patch > > > > when applying? > > > > > > > > I think we can keep the DL_FLAG_AUTOREMOVE_CONSUMER in the > > > > device_link_add() > > > > call as it will be ignored if fw_devlinks already created the link but > > > > might > > > > be > > > > important if the kernel command line fw_devlink is set to 'off'. > > > > > > > > Or maybe, as Saravan mentioned in his reply we can just pass > > > > DL_FLAG_MANAGED > > > > as > > > > > > Forget about this as I just realized DL_FLAG_MANAGED is not a proper flag we > > > can > > > pass... > > > > > > - Nuno Sá > > > > > > > Discussion has gotten too complex - so even if no changes, send a v8 dropping > > the patch (assuming that's the end conclusion!) > > > > Dropping the patch is pretty much decided is the right thing to do. The only > thing I'm still thinking is that if I should use AUTOPROBE_CONSUMER (as > fw_devlinks) instead when creating the link. With that flag, any IIO consumer of > the IIO backend will be automatically probed as soon as the backend is probed. > It also has the advantage of keeping the link around (vs AUREMOVE_CONSUMER which > deletes the link when the IIO consumer is gone) so in the re-bind case we can > avoid useless EPROBE_DEFERs. > > It's a nitpicky thing in the end and not really that important. Moreover because > I expect that in 99% of the usecases, fw_devlinks will already create our link > so the flags we pass in our call don't really matter. Note that our explicit > call is still important (as I explained to Saravan in another email) as we based > the design with the assumption that the consumer can never be around without the > backend. And in the case we have modules, we can have the links created by > fw_devlinks removed unless we explicitly call device_link_add() (and that would > mean our previous assumptions are no longer valid). I saw your reasoning, but technically there are still gaps in the forced unbinding of consumers. If the consumer doesn't have a bus or doesn't have an explicit driver, it won't be force unbound. But this is all generic issues that need to be resolved at a driver core level. I'd really prefer drivers/frameworks not duplicating it all over. How about just checking for fw_devlink=on or better and not probe your supplier if it's not set? Or not allow unbinding your supplier if fw_devlink=on or better isn't there? -Saravana
