linux-kernel - Re: [PATCH] drm/ssd130x: Fix possible uninitialized usage of crtc

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Message-ID: <CAMuHMdXHq6yE14YqA+GNj=V79Z1rYTK=8Dx5WWw3RczrzMy21A@mail.gmail.com>
Date:   Tue, 31 Oct 2023 14:00:06 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Maxime Ripard <mripard@...nel.org>
Cc:     Javier Martinez Canillas <javierm@...hat.com>,
        Jocelyn Falempe <jfalempe@...hat.com>,
        linux-kernel@...r.kernel.org,
        Thomas Zimmermann <tzimmermann@...e.de>,
        dri-devel@...ts.freedesktop.org,
        Dan Carpenter <dan.carpenter@...aro.org>
Subject: Re: [PATCH] drm/ssd130x: Fix possible uninitialized usage of
 crtc_state variable

Hi Maxime,

On Tue, Oct 31, 2023 at 12:53 PM Maxime Ripard <mripard@...nel.org> wrote:
> On Tue, Oct 31, 2023 at 12:27:05PM +0100, Javier Martinez Canillas wrote:
> > Geert Uytterhoeven <geert@...ux-m68k.org> writes:
> > >> >> Pushed to drm-misc (drm-misc-next). Thanks!
> > >> >
> > >> > Looks like you introduced an unintended
> > >> >
> > >> >     (cherry picked from commit 9e4db199e66d427c50458f4d72734cc4f0b92948)
> > >> >
> > >> > ?
> > >>
> > >> No, that's intended. It's added by the `dim cherry-pick` command, since I
> > >> had to cherry-pick to drm-misc-next-fixes the commit that was already in
> > >> the drm-misc-next branch.
> > >>
> > >> You will find that message in many drm commits, i.e:
> > >>
> > >> $ git log --oneline --grep="(cherry picked from commit" drivers/gpu/drm/ | wc -l
> > >> 1708
> > >
> > > Ah, so that's why it's (way too) common to have merge conflicts between
> > > the fixes and non-fixes drm branches :-(

> That's also not as bad as Geert put it: merging two branches with the
> exact same commit applied won't create conflict. If the two commits
> aren't exactly the same then we can indeed create conflicts, but that
> would have been the case anyway with or without the "double-commits"

Oh it is, as soon as one branch receives more commits that make changes
to the same location.  Which is fairly common, too, to the point
that I am surprised when merging a drm for-next branch does not trigger
a conflict...

Cfr. the conflict I had to resolve this morning between commit
64ffd2f1d00c6235 ("drm/amd: Disable ASPM for VI w/ all Intel systems")
already upstream, and commits e5f52a84bf0a8170 ("drm/amd: Disable ASPM
for VI w/ all Intel systems") and follow-up 2757a848cb0f1848
("drm/amd: Explicitly disable ASPM when dynamic switching disabled")
in drm/drm-next.

Note that none of 64ffd2f1d00c6235 and 2757a848cb0f1848 has a "cherry
picked from commit" line in the commit description.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds