linux-kernel - Re: [PATCH v2 00/10] drivers, provide a way to add sysfs groups easily

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Date:   Wed, 31 Jul 2019 06:46:38 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        Richard Gong <richard.gong@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Borislav Petkov <bp@...en8.de>,
        Darren Hart <dvhart@...radead.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Ingo Molnar <mingo@...hat.com>,
        Sudeep Holla <sudeep.holla@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tony Prisk <linux@...sktech.co.nz>,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-fbdev@...r.kernel.org,
        linux-input@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        x86@...nel.org
Subject: Re: [PATCH v2 00/10] drivers, provide a way to add sysfs groups
 easily

On Wed, Jul 31, 2019 at 04:38:40PM +0300, Andy Shevchenko wrote:
> On Wed, Jul 31, 2019 at 06:10:45AM -0700, Dmitry Torokhov wrote:
> > On Wed, Jul 31, 2019 at 02:43:39PM +0200, Greg Kroah-Hartman wrote:
> > > This patch originally started out just as a way for platform drivers to
> > > easily add a sysfs group in a race-free way, but thanks to Dmitry's
> > > patch, this series now is for all drivers in the kernel (hey, a unified
> > > driver model works!!!)
> > > 
> > > I've only converted a few platform drivers here in this series to show
> > > how it works, but other busses can be converted after the first patch
> > > goes into the tree.
> > > 
> > > Here's the original 00 message, for people to get an idea of what is
> > > going on here:
> > > 
> > > If a platform driver wants to add a sysfs group, it has to do so in a
> > > racy way, adding it after the driver is bound.  To resolve this issue,
> > > have the platform driver core do this for the driver, making the
> > > individual drivers logic smaller and simpler, and solving the race at
> > > the same time.
> > > 
> > > All of these patches depend on the first patch.  I'll take the first one
> > > through my driver-core tree, and any subsystem maintainer can either ack
> > > their individul patch and I will be glad to also merge it, or they can
> > > wait until after 5.4-rc1 when the core patch hits Linus's tree and then
> > > take it, it's up to them.
> > 
> > Maybe make an immutable branch off 5.2 with just patch 1/10 so that
> > subsystems (and the driver core tree itself) could pull it in at their
> > leisure into their "*-next" branches and did not have to wait till 5.4
> > or risk merge clashes?
> 
> Isn't cherry-pick enough for one patch?

With cherry-picking you run into potential merge conflicts if Greg
changes more code in the same area. Plus, once everything is merged into
Linus' tree, there will be N git commits adding the same thing.

With immutable branch there is a single git commit, so merges are
guaranteed to be clean, with no conflicts.

Thanks.

-- 
Dmitry