Re: [PATCH] mmc: tegra: fix SDR50 tuning override

[Thierry Reding <thierry.reding@gmail.com>]

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On Mon, Jan 06, 2020 at 01:27:45PM +0100, Greg Kroah-Hartman wrote:
> On Mon, Jan 06, 2020 at 01:07:18PM +0100, Thierry Reding wrote:
> > On Thu, Jan 02, 2020 at 11:30:50AM +0100, Michał Mirosław wrote:
> > > Commit 7ad2ed1dfcbe inadvertently mixed up a quirk flag's name and
> > > broke SDR50 tuning override. Use correct NVQUIRK_ name.
> > > 
> > > Fixes: 7ad2ed1dfcbe ("mmc: tegra: enable UHS-I modes")
> > > Depends-on: 4f6aa3264af4 ("mmc: tegra: Only advertise UHS modes if IO regulator is present")
> > > Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
> > > ---
> > >  drivers/mmc/host/sdhci-tegra.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > Oh my... good catch!
> > 
> > Reviewed-by: Thierry Reding <treding@nvidia.com>
> > 
> > I also ran this through our internal test system and all tests pass, so
> > also:
> > 
> > Tested-by: Thierry Reding <treding@nvidia.com>
> > 
> > I'm not sure if that "Depends-on:" tag is anything that's recognized
> > anywhere. It might be better to turn that into an additional "Fixes:"
> > line. Adding Greg to see if he has a standard way of dealing with this
> > kind of dependency.
> > 
> > Greg, what's your preferred way to handle these situations? I think the
> > intention here was to describe that the original error was introduced by
> > commit 7ad2ed1dfcbe ("mmc: tegra: enable UHS-I modes"), but then commit
> > 4f6aa3264af4 ("mmc: tegra: Only advertise UHS modes if IO regulator is
> > present") moved that code around, so this patch here will only be back-
> > portable until the latter commit, but should be backported until the
> > former.
> 
> The stable kernel rules document says how to handle this, but the
> "depends on" commit id in the comment to the right of the stable@k.o cc:
> line in the changelog area.

That only mentions "static" prerequisites needed by the patch, but what
if the prerequisites change depending on version?

Could I do something like this:

	Cc: <stable@vger.kernel.org> # 4.4.x: abcdef: ...
	Cc: <stable@vger.kernel.org> # 4.9.x: bcdefa: ...
	Cc: <stable@vger.kernel.org>

Would that mean that the patch is selected for all stable releases
(because of the last line with no version prerequisite) but when applied
for stable-4.4 the abcdef patch gets pulled in and for stable-4.9 the
bcdefa dependency is applied before the patch?

I suppose this is perhaps a bit of an exotic case, but it might be good
to document it specifically because it might be fairly rare. I can draft
a change if you think this is useful to add.

Thierry

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