On Sun, Jun 13, 2021 at 12:13 AM Sander Vanheule <sander@xxxxxxxxxxxxx> wrote: > > Some chips have the read-only input and write-only output data registers > aliased to the same offset. As a result it is not possible to perform > read-modify-writes on the output values, when a line is still configured > as input. > > Add a quirk for aliased data registers, and document how the regmap > should be set up for correct operation. I still believe that there is no issue with gpio-regmap and we don't need any quirk there. The issue is in the regmap APIs (implementation) itself. Hardware with the concept of reading X / writing Y at the same offset is okay per se. regmaps doesn't support it properly and should be fixed (amended) in a way that you provide this kind of register description thru regmap configuration or so. I expressed the idea of trying to implement regmap-8250 as an example of the support for such hardware. And OTOH that this kind of hardware is not unusual. -- With Best Regards, Andy Shevchenko
