linux-kernel - Re: [PATCH v5 00/20] gpio: cdev: add uAPI v2

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Message-ID: <20200910140949.GV1891694@smile.fi.intel.com>
Date:   Thu, 10 Sep 2020 17:09:49 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Bartosz Golaszewski <bgolaszewski@...libre.com>
Cc:     Kent Gibson <warthog618@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH v5 00/20] gpio: cdev: add uAPI v2

On Tue, Sep 01, 2020 at 11:28:13AM +0200, Bartosz Golaszewski wrote:
> On Sat, Aug 29, 2020 at 3:35 AM Kent Gibson <warthog618@...il.com> wrote:
> >
> > On Fri, Aug 28, 2020 at 04:37:19PM +0200, Linus Walleij wrote:
> > > On Fri, Aug 28, 2020 at 12:47 AM Kent Gibson <warthog618@...il.com> wrote:
> > >
> > > > The particular use case I am considering is one I had been asked about -
> > > > changing a requested line from input with edge detection to output, and
> > > > vice versa. Losing interrupts isn't really an issue for this use case -
> > > > it is expected.  Yet the current implementation requires a re-request.
> > >
> > > This is possible to do for in-kernel users, but I don't know if that makes
> > > sense for userspace. It is for one-offs and prototyping after all, there
> > > is no need (IMO) to make it overly convenient for users to implement
> > > all kind of weirdness in userspace unless there is a very real use case.
> > >
> >
> > Fair point - in fact it is the same one that made me reconsider why I
> > was so concerned about potentially losing an edge event in a few rare
> > corner cases.
> >
> > Another point for this change are that it actually simplifies the kernel
> > code, as it takes as much code to detect and filter these cases as it
> > does to include them in the normal flow.
> >
> > I had a play with it yesterday and the change removes two whole
> > functions, gpio_v2_line_config_change_validate() and
> > gpio_v2_line_config_has_edge_detection() at the expense of making
> > debounce_update() a little more complicated. I'm happy to put together a
> > v6 that incorporates those changes if there aren't any strenuous
> > objections - we can always revert to v5.  Or I could mail the couple of
> > patches I've made and if they seem reasonable then I could merge them
> > into this set?
> >
> > Cheers,
> > Kent.
> 
> I personally like v6 more. The code is more elegant and we've also
> tried limiting GPIO chardev features before and now we're doing v2 so
> let's not make the same mistake twice. :)
> 
> I'll try to review v6 in detail later today.

Let me briefly review to this. Can you remind which patch has a top level
description of what features are provided in comparison to uAPI v1?
(Btw, do we have some kind of comparison table?)


-- 
With Best Regards,
Andy Shevchenko