Re: [Ksummit-discuss] [MAINTAINER SUMMIT] Distribution kernel bugzillas considered harmful

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Iwai-san,

On Tue, Sep 18, 2018 at 10:37 PM Takashi Iwai <tiwai@suse.de> wrote:
> On Tue, 18 Sep 2018 15:43:08 +0200,
> Martin K. Petersen wrote:
> > Sorry I'm a little late to the game here. Been out on vacation.
> >
> > > We order patches in our trees in the same git-topological-ordering as they
> > > are upstream. It has a lot of benefits, most importantly: it doesn't
> > > introduce artificial conflicts that don't exist in reality.
> > >
> > > In order to achieve that, we of course need 1:1 mapping between our
> > > patches and upstream commits.  Rebases destroy that mapping.
> > >
> > > And in some areas (scsi is one, but not the only one), we basically had no
> > > other choice than considering maintainer's tree to be already "upstream
> > > enough", without waiting for Linus' tree merge.
> >
> > When I discussed this with Johannes a little while ago, I suggested you
> > guys used git patch-id to track patches instead of commit ids. That's
> > how we track patches applied across many different trees internally.
> > Works much better than using the upstream sha.
>
> What is git patch id?  Is there any internal patch tag?

It's the output of "git patch-id", which is a hash of the patch, without
including its dependencies.  This allows to match identical commits in
different branches, and is what "git cherry" and "git rebase" use to detect
already applied patches.

Example (from v4.18.y):

$ git show -s e496c9a4c17d4a97ed8d222f368f3b8ad8133fb9
commit e496c9a4c17d4a97ed8d222f368f3b8ad8133fb9
Author: Robert Munteanu <rombert@apache.org>
Date:   Tue Jun 19 11:20:40 2018 +0300

    HID: redragon: fix num lock and caps lock LEDs

    commit dc9b8e85ed95cbe7e3ad0eabb5b48d617bbc365e upstream.

    The redragon asura keyboard registers two input devices. The initial commit
    85455dd906d5 ("HID: redragon: Fix modifier keys for Redragon Asura
Keyboard")
    considered this an error and prevented one of the devices from registering.
    However, once this is done the num lock and caps lock leds no
longer toggle on
    and off, although the key functionality is not affected.

    This commit removes the code that prevents the input device
    registration and restores the num lock and caps lock LEDs.

    Fixes: 85455dd906d5 ("HID: redragon: Fix modifier keys for
Redragon Asura Keyboard")
    Signed-off-by: Robert Munteanu <rombert@apache.org>
    Signed-off-by: Jiri Kosina <jkosina@suse.cz>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

$ git show e496c9a4c17d4a97ed8d222f368f3b8ad8133fb9 | git patch-id
9d4546a92b459de7249748c0a38b50c989f13bd1
e496c9a4c17d4a97ed8d222f368f3b8ad8133fb9
$ git show dc9b8e85ed95cbe7e3ad0eabb5b48d617bbc365e | git patch-id
9d4546a92b459de7249748c0a38b50c989f13bd1
dc9b8e85ed95cbe7e3ad0eabb5b48d617bbc365e

So both commits are identical, as they have the same patch ID.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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