On Thu, Nov 17, 2022 at 11:34:06AM +0000, Mark Brown wrote: > On Wed, Nov 16, 2022 at 11:07:48AM -0800, Dmitry Torokhov wrote: > > On Wed, Nov 16, 2022 at 10:36:27AM +0000, Mark Brown wrote: > > > > How are we ensuring that people have described signals as active > > > low/high in existing DTs, and are we positive that the signal is > > > described as active low for all devices? In particular if the > > > signal is described as a reset signal then it's active high even > > > if we want it low while the device is actually in use. > > > I have been going through in-kernel DTSes and adjusting ones that are > > incorrect. For external ones I think we should take a pragmatic approach > > and say that if driver has last non-mechanical update in 2014 and there > > are no users submitted to mainline since then (as this one), then it is > > highly unlikely that devices currently using this component/codec will > > be updated to the 6.2+ kernel even if they are still in service. And if > > this does happen the breakage will be immediately obvious as we'll keep > > the codec in reset state. > > > But if you really want to I can add quirk(s) to gpiolib forcing this > > line to be treated as active-low regardless of what specified in DTS. > > This kind of negates benefit of going to gpiod though. > > That doesn't address the bit about checking that the device > describes the signal as active low in hardware - it's assuming > that the signal is described by the device as an active low > reset and not for example as a shutdown signal. Huh? If we add a quirk to gpiolib to treat the signal as active low (i.e. preserve current driver behavior - I am talking about this particular peripheral here, not treating everything as active low of course). > > TBH I'm not thrilled about just randomly breaking ABI > compatibility for neatness reasons, it's really not helping > people take device tree ABI compatibility seriously. Yes, I freely admit I do not take device tree ABI compatibility seriously. IMO, with the exception of a few peripherals, it is a solution in search of a problem, and we declared stability of it too early, before we came up with reasonable rules for how resources should be described. I strongly believe that in vast majority of cases devices with out-of-tree DTs will not be updated to upstream kernels as this requires significant engineering effort and vendors usually not interested in doing that. Thanks. -- Dmitry
