linux-kernel - Re: [PATCH AUTOSEL for 4.9 002/219] spi/bcm63xx: make spi subsystem aware of message size limits

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Message-ID: <20180306142012.GB13586@sirena.org.uk>
Date:   Tue, 6 Mar 2018 14:20:12 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Jonas Gorski <jonas.gorski@...il.com>
Cc:     Sasha Levin <Alexander.Levin@...rosoft.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH AUTOSEL for 4.9 002/219] spi/bcm63xx: make spi subsystem
 aware of message size limits

On Tue, Mar 06, 2018 at 02:42:43PM +0100, Jonas Gorski wrote:
> On 5 March 2018 at 21:35, Mark Brown <broonie@...nel.org> wrote:

> > It's exposing more capability information but it's in the "how did this
> > ever work without the fix" range, and I'd worry that this might cause us
> > to do something like start exercising handling code in client drivers
> > that had never been tested.  Not that I can immediately see any client
> > drivers in mainline that actually pay attention...  :/

> I would assume that most spi client drivers use short messages, so
> they aren't affected unless the max message size is really short.
> m25p80 on the other hand will do arbitrarily large transfers/reads, so
> there it was supported first.

There's a bunch of SPI drivers that do firmware downloads which I'd
expect to be affected, the limit the device has is tiny so it's
relatively easy to bump into it.  It's very rare for devices to be so
limited so unfortunately client drivers don't generally check though.

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