linux-kernel - Re: [PATCH 4.9 11/66] spi/bcm63xx: make spi subsystem aware of message size limits

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Message-ID: <20180720133946.GA22550@kroah.com>
Date:   Fri, 20 Jul 2018 15:39:46 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Jonas Gorski <jonas.gorski@...il.com>,
        Amit Pundir <amit.pundir@...aro.org>
Subject: Re: [PATCH 4.9 11/66] spi/bcm63xx: make spi subsystem aware of
 message size limits

On Fri, Jul 20, 2018 at 01:34:43PM +0100, Mark Brown wrote:
> On Fri, Jul 20, 2018 at 02:13:28PM +0200, Greg Kroah-Hartman wrote:
> 
> > The bcm63xx SPI controller does not allow manual control of the CS
> > lines and will toggle it automatically before and after sending data,
> > so we are limited to messages that fit in the FIFO buffer. Since the CS
> > lines aren't available as GPIOs either, we will need to make slave
> > drivers aware of this limitation so they can handle them accordingly.
> 
> Same review comment as before: this will ask other code (which
> presumably never worked?) to change how they use the hardware in order
> to cope with the limiations which seems a bit risky to me given that
> limits like this are fairly rare so that code isn't super well exercised
> in general.

Ok, now I think I understand this better.  I've now dropped this, and
the follow-on fixup patch from the 4.9 queue.  Thanks for being patient
with me.

greg k-h