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Date: Wed, 13 Dec 2023 23:11:34 +0800
From: Kent Gibson <warthog618@gmail.com>
To: Andy Shevchenko <andy@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-gpio@vger.kernel.org, brgl@bgdev.pl,
	linus.walleij@linaro.org
Subject: Re: [PATCH 3/4] gpiolib: cdev: reduce locking in
 gpio_desc_to_lineinfo()
Message-ID: <ZXnJply1tPnTN_-O@rigel>
References: <20231212054253.50094-1-warthog618@gmail.com>
 <20231212054253.50094-4-warthog618@gmail.com>
 <ZXm4C7KVkMwL4_sX@smile.fi.intel.com>
 <ZXm6oHjb7CRZ8-0f@rigel>
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In-Reply-To: <ZXm6oHjb7CRZ8-0f@rigel>

On Wed, Dec 13, 2023 at 10:07:28PM +0800, Kent Gibson wrote:
> On Wed, Dec 13, 2023 at 03:56:27PM +0200, Andy Shevchenko wrote:
> > On Tue, Dec 12, 2023 at 01:42:52PM +0800, Kent Gibson wrote:
> > > Reduce the time holding the gpio_lock by snapshotting the desc flags,
> > > rather than testing them individually while holding the lock.
> > >
> > > Accept that the calculation of the used field is inherently racy, and
> > > only check the availabilty of the line from pinctrl if other checks
> > > pass, so avoiding the check for lines that are otherwise in use.
> >
> > ...
> >
> > > -	bool ok_for_pinctrl;
> > > -	unsigned long flags;
> > > +	unsigned long iflags, dflags;
> >
> > With a preliminary conversion to cleanup.h this whole change becomes cleaner,
> > no?
> >
>
> You mean the scoped guards?  Dunno - haven't used them.
> Care to provide more detail?
>

Ok, so changing the spin_lock/unlock to

       scoped_guard(spinlock_irqsave, &gpio_lock) {
       ...
       }

you no longer need the iflags at all, and can rename dflags to flags.
Got it.

Cheers,
Kent.