linux-kernel - Re: [PATCH v2 10/11] gpiolib: add new ioctl() for monitoring changes in line info

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Message-ID: <CAMRc=Me4xWsQggmr=BvJrA9-FnPkxFkOYsRTsSXCtyNwFnsHNw@mail.gmail.com>
Date:   Thu, 5 Dec 2019 14:47:29 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Kent Gibson <warthog618@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 10/11] gpiolib: add new ioctl() for monitoring changes
 in line info

czw., 5 gru 2019 o 11:27 Andy Shevchenko <andy.shevchenko@...il.com> napisał(a):
>
> On Thu, Dec 5, 2019 at 11:42 AM Bartosz Golaszewski
> <bgolaszewski@...libre.com> wrote:
> > śr., 4 gru 2019 o 23:34 Andy Shevchenko <andy.shevchenko@...il.com> napisał(a):
> > > On Wed, Dec 4, 2019 at 6:03 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:
>
> > > > +struct gpioline_info_changed {
> > > > +       __u64 timestamp;
> > > > +       __u32 event_type;
> > > > +       struct gpioline_info info;
> > > > +       __u32 padding[4]; /* for future use */
> > > > +};
> > >
> > > Has this been tested against 64-bit kernel / 32-bit userspace case?
> > >
> >
> > No. Since this is a new thing - do you think it's possible to simply
> > arrange the fields or add padding such that the problem doesn't even
> > appear in the first place?
>
> Yes. this can be done, though be careful about potential endianess
> issues (the ABI must be tested on BE as well).
>
> So, the test cases, I can imagine of, should include (k - kernel, u - user):
> - 64k-64u: LE and BE
> - 64k-32u: LE and BE
> - 32k-32u: LE and BE

I usually use qemu VMs built with yocto for testing but I don't see
any way of creating a 32-bit user-space with 64-bit kernel. Any ideas
on how to prepare a testing environment?

Bart

>
> --
> With Best Regards,
> Andy Shevchenko