[PATCH v5] drm/panel: db7430: Add driver for Samsung DB7430

[Doug Anderson]

Hi,

On Thu, Jun 10, 2021 at 3:39 PM Linus Walleij <linus.walleij at linaro.org> wrote:
>
> On Fri, Jun 11, 2021 at 12:30 AM Doug Anderson <dianders at chromium.org> wrote:
>
> > > +       mipi_dbi_command(dbi, MIPI_DCS_SET_ADDRESS_MODE, 0x0a);
> >
> > I would still prefer it if there was some type of error checking since
> > SPI commands can fail and could potentially fail silently. What about
> > at least this (untested):
> >
> > #define db7430_dbi_cmd(_db, _cmd, _seq...) \
> >   do {
> >     int _ret = mipi_dbi_command(_db->dbi, _cmd, _seq);
> >     if (_ret)
> >       dev_warn(_db->dev, "DBI cmd %d failed (%d)\n", _cmd, _ret);
> >   } while (0)
> >
> > Then at least you know _something_ will show up in the logs if there's
> > a transfer failure instead of silence?
> >
> > If you truly don't want the error checking then I guess I won't
> > insist, but it feels like the kind of thing that will bite someone
> > eventually... In any case, I'm happy to add this now (especially since
> > the DBI stuff is Acked now).
>
> This looks more like something that should be done in
> mipi_dbi_command() in include/drm/drm_mipi_dbi.h
> which claims:
>
>  * Returns:
>  * Zero on success, negative error code on failure.
>  */
>
> But no it does not return anything:
>
> #define mipi_dbi_command(dbi, cmd, seq...) \
> ({ \
>         const u8 d[] = { seq }; \
>         mipi_dbi_command_stackbuf(dbi, cmd, d, ARRAY_SIZE(d)); \
> })
>
> I'll fix up the include and apply then we can think about
> what to do with mipi_dbi_command().

Are you sure that doesn't work? Isn't the return value of a macro the
last expression? In this case the return value of
mipi_dbi_command_stackbuf() should just flow through.

-Doug