linux-kernel - Re: [PATCH 2/7] mfd: cros_ec: spi: Add mutex to cros_ec

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Date:	Fri, 18 Apr 2014 15:43:23 -0600
From:	Simon Glass <sjg@...omium.org>
To:	Doug Anderson <dianders@...omium.org>
Cc:	Lee Jones <lee.jones@...aro.org>,
	Stephen Warren <swarren@...dia.com>,
	Wolfram Sang <wsa@...-dreams.de>,
	Andrew Bresticker <abrestic@...omium.org>,
	Dylan Reid <dgreid@...omium.org>,
	Olof Johansson <olof@...om.net>,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	lk <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/7] mfd: cros_ec: spi: Add mutex to cros_ec_spi

Hi Doug,

On 18 April 2014 15:15, Doug Anderson <dianders@...omium.org> wrote:
>
> Simon,
>
> On Fri, Apr 18, 2014 at 10:28 AM, Simon Glass <sjg@...omium.org> wrote:
> > Hi Doug,
> >
> > On 17 April 2014 11:59, Doug Anderson <dianders@...omium.org> wrote:
> >> The main transfer function for cros_ec_spi can be called by more than
> >> one client at a time.  Make sure that those clients don't stomp on
> >> each other by locking the bus for the duration of the transfer
> >> function.
> >
> > Is there no lock at the cros_ec layer?
>
> Not with what's upstream.
>
> Locally in the Chromium OS tree:
>
> * You can see that Bill removed the dev_lock at
> <https://chromium-review.googlesource.com/#/c/57051/> since it wasn't
> used.
>
> * Andrew moved to a common locking scheme later in
> <https://chromium-review.googlesource.com/#/c/170747/> (thus adding
> roughly the same lock back and using it), but in order to do that
> we've got a dozen pathces in between, some of which are big
> reorganizations.  This includes at least:
>
> 6820b91 CHROMIUM: cros_ec: Tweak struct cros_ec_device for clarity
> 5e8e562 CHROMIUM: Use struct cros_ec_command to communicate with the EC
> 9e7db82 CHROMIUM: cleanup: remove unused fields from struct cros_ec_device
> 866e62d CHROMIUM: cleanup: Remove EC wrapper functions.
> 8a372b2 cros_ec: move locking into cros_ec_cmd_xfer
> 981c4aa cros_ec: stop calling ->cmd_xfer() directly
>
> I think we should take in some of those other changes but I'd rather
> get correctness in first (since people are wanting to use this driver
> in upstream kernel) and get cleanups posted after this lands.  I was
> also trying not to spam the list with a 20-patch series...

That explains it, thank you. I should have guessed that for myself.

Reviewed-by: Simon Glass <sjg@...omium.org>

Regards,
Simon
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