Re: gpiolib: why does gpio_set_bias() suppress ENOTSUPP?

[Kent Gibson <warthog618@xxxxxxxxx>]

On Mon, Apr 04, 2022 at 12:23:18PM +0300, Andy Shevchenko wrote:
> On Sun, Apr 3, 2022 at 6:34 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
> > On 4/2/22 03:45, Kent Gibson wrote:
> > > On Fri, Apr 01, 2022 at 12:36:57PM +0200, Hans de Goede wrote:
> 
> ...
> 
> > > Probably best to extend the uAPI to add a strict mode and leave
> > > existing usage unchanged.
> >
> > Agreed, adding a strict mode to the uAPI seems best.
> >
> > And if you do it this way, you should probably also make
> > the kernel log (using a ratelimited log function) why (e.g.
> > bias setting not supported)  the call is failing since errno is
> > not going to tell the user enough here I think.
> 
> ...which reminds me this one: https://lwn.net/Articles/657341/
> 

In this case I'd be more inclined to return a sanitised config along
with the error code.  So the user gets "the config you requested isn't
doable, but this one is". They could even repeat the request with the
sanitised config, though I'm not sure if that would provide any benefit
compared to just not requesting strict in the first place.

Cheers,
Kent.

> -- 
> With Best Regards,
> Andy Shevchenko