On Wed, Nov 16, 2022 at 04:41:30PM +0100, Michael Walle wrote: > Am 2022-11-13 14:21, schrieb William Breathitt Gray: > > On Sun, Nov 13, 2022 at 02:40:17PM +0200, Andy Shevchenko wrote: > > > On Thu, Nov 10, 2022 at 08:55:50PM -0500, William Breathitt Gray > > > wrote: > > > > If you only have reg_dat_base set, then it is input-only; if you only > > > > have reg_set_base set, then it is output-only. Thus, we can always set > > > > gpio_chip get_direction to gpio_regmap_get_direction and return > > > > GPIO_LINE_DIRECTION_IN/GPIO_LINE_DIRECTION_OUT given the respective > > > > register base addresses configuration. > > > > > > Seems legit to me. Have you checked if we have any gpio-regmap > > > drivers that > > > have something like this in their configuration already? In such > > > cases we need > > > to be sure they behave as expected. > > > > > > From the code perspective: > > > Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> > > > > I see gpio-sl28cpld has two device types SL28CPLD_GPO (output-only) and > > SL28CPLD_GPI (input-only); gpio-tn48m similarly has two device types > > TN48M_GPO (output-only) and TN48M_GPI (input-only). It doesn't look like > > the change in this patch will cause problems for them, but I'll let > > Michael Walle and Robert Marko comment if they see issues here. > > For the sl28cpld driver this shouldn't be a problem. So for that > Acked-by: Michael Walle <michael@xxxxxxxx> > > But back when I wrote gpio-regmap the bgpio served as a blue print. > There is the same handling. If you look at gpiolib-sysfs.c there > is a comment about the direction property: > > * MAY BE OMITTED if kernel won't allow direction changes > > So from a gpiolib/sysfs POV I'm not sure about this change. Does > get_direction == NULL means setting the direction isn't possible? > OTHO there is a fat "MAY" :) > > Which brings me to the question of "why this change?". The commit > message doesn't mention it. Just out of curiosity. > > -michael Currently, the 104-idi-48 module implements a get_direction() callback that is executed in situations such as gpiod_get_direction() which aren't necessarily related to sysfs. In this patch series, the 104-idi-48 module is migrated to the gpio_regmap API, but loses this get_direction() support because it's an input-only configuration. The purpose of this patch is to prevent that regression by supporting get_direction() for input-only/output-only configurations. William Breathitt Gray
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