linux-kernel - Re: [PATCH] mmc: tegra: fix SDR50 tuning override

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Message-ID: <20200107093715.GB1028311@kroah.com>
Date:   Tue, 7 Jan 2020 10:37:15 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        linux-mmc@...r.kernel.org, Ulf Hansson <ulf.hansson@...aro.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Thierry Reding <treding@...dia.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Lucas Stach <dev@...xeye.de>, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mmc: tegra: fix SDR50 tuning override

On Mon, Jan 06, 2020 at 02:37:03PM +0100, Thierry Reding wrote:
> 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@...e.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@...dia.com>
> > > 
> > > I also ran this through our internal test system and all tests pass, so
> > > also:
> > > 
> > > Tested-by: Thierry Reding <treding@...dia.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@...r.kernel.org> # 4.4.x: abcdef: ...
> 	Cc: <stable@...r.kernel.org> # 4.9.x: bcdefa: ...
> 	Cc: <stable@...r.kernel.org>

Yes.

> 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?

Yes.

> 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.

I thought this was already in there, as others have done it in the past.

It's a _very_ exotic case, I wouldn't worry about it, just document it
like this, and if I have problems applying the patches to stable I'll be
sure to let you know and you can always tell me then.  That's usually
the easiest thing to do anyway :)

thanks,

greg k-h