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

From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-kernel@vger.kernel.org,
	Richard Gong <richard.gong@linux.intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	Borislav Petkov <bp@alien8.de>,
	Darren Hart <dvhart@infradead.org>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Ingo Molnar <mingo@redhat.com>,
	Sudeep Holla <sudeep.holla@arm.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Tony Prisk <linux@prisktech.co.nz>,
	dri-devel@lists.freedesktop.org,
	linux-arm-kernel@lists.infradead.org,
	linux-fbdev@vger.kernel.org, linux-input@vger.kernel.org,
	platform-driver-x86@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH v2 00/10] drivers, provide a way to add sysfs groups easily
Date: Wed, 31 Jul 2019 06:46:38 -0700	[thread overview]
Message-ID: <20190731134638.GD147138@dtor-ws> (raw)
In-Reply-To: <20190731133840.GN23480@smile.fi.intel.com>

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