On Tue, 11 Oct 2022 09:10:21 +0000 "Vaittinen, Matti" <Matti.Vaittinen@xxxxxxxxxxxxxxxxx> wrote: > On 10/10/22 09:15, Andy Shevchenko wrote: > > On Sun, Oct 09, 2022 at 01:33:51PM +0100, Jonathan Cameron wrote: > >> On Thu, 6 Oct 2022 21:32:11 +0300 Andy Shevchenko > >> <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote: > >>> On Thu, Oct 06, 2022 at 05:38:14PM +0300, Matti Vaittinen wrote: > > > > ... > > > >>>> +module_param(g_kx022a_use_buffer, bool, 0); > >>>> +MODULE_PARM_DESC(g_kx022a_use_buffer, + "Buffer samples. Use > >>>> at own risk. Fifo must not overflow"); > >>> > >>> Why?! We usually do not allow module parameters in the new code. > >> > >> Badly broken hardware - was my suggestion. Alternatives if there > >> are usecases that need to use the fifo, but it can wedge hard in a > >> fashion that is impossible to prevent from the driver? My gut > >> feeling is still drop the support entirely with a strong comment in > >> the code that the hardware is broken in a fashion we don't know how > >> to work around. > > I did some quick study regarding couple of other Kionix sensors. (like > KX122 and old KX022 - without the 'A'). It seems to me that the register > interfaces between many of the sensors are largely identical. Extending > the driver to support those seems pretty straightforward (scales and > resolution may need tweaking, as does the FIFO size) but register > contents and even offsets are largely identical. Last kionix part I had was a kxsd9 and I don't recall that having a fifo so obviously didn't hit this issue. > > As said, it seems the Kionix sensors may have different size of internal > FIFOs, or even no FIFO at all. So, maybe we could provide a > "kionix,fifo-enable" flag (or even "kionix,fifo-size") from device-tree? For device where we don't have reports of this issue, that should be derived from the compatible (or even better a whoami register if there is one). The driver should know the fifo-size if it isn't discoverable. > This would be a way to have the FIFO disabled by default and warn users > via dt-binding docs if they decide to explicitly enable the FIFO. > (Besides, I believe the FIFO is usable on at least some of the Kionix > sensors - because I've heard it is used on a few platforms). > > This could give us safe defaults while not shutting the doors from those > who wish to use the FIFO. Sure we need a buy-in from Krzysztof / Rob, > but that may be less of an obstacle compared to the module param if Greg > is so strongly oppsoing those. (And the dt-property could also provide > some technical merites as these sensors seem to really have differencies > in FIFOs). I'm dubious about having this for known broken parts - but I guess you can propose it and see what the dt-maintainers say. I don't want to see fifo size in the dt binding though. > > > > > I also would drop this from upstream and if anybody curious, provide > > some kind of GitHub gist for that. > > Well, I think we all agree that downstream code hosted in some > unofficial github repositories are rarely that valuable. They're less > reliable, less tested, less reviewed, less secure and pretty much > impossible to maintain in a way that interested user could get a version > matching his preferred kernel. > > There are reasons why I (people) keep sending the drivers to upstream - > and why some companies even spend $$ for that. Having this feature in > downstream repo is not nearly on same page for user's point of view as > is having the support upstream. It's not really support if it comes with big warnings and potentially we even taint the kernel of someone turns it on... > > > Also it needs some communication > > with a vendor to clarify the things. > > I do communication with the vendor on a daily basis :] Nowadays Kionix > is part of ROHM, and Finland SWDC has been collaboration with Kionix > even before they "merged" (but I have not been part of the "sensor team" > back then). > > Unfortunately, reaching the correct people inside the company is hard > and occasionally impossible - long story... :) Jonathan
