linux-kernel - Re: [PATCH] spi: fix cs

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Message-ID: <20200316151320.GI5010@sirena.org.uk>
Date:   Mon, 16 Mar 2020 15:13:20 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Michał Mirosław <mirq-linux@...e.qmqm.pl>
Cc:     linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] spi: fix cs_change for last transfer

On Mon, Mar 16, 2020 at 03:34:55PM +0100, Michał Mirosław wrote:
> On Mon, Mar 16, 2020 at 12:17:50PM +0000, Mark Brown wrote:

> > This is the opposite of the intended behaviour - we want to deassert
> > chip select at the end of the message unless cs_change is set on the
> > last transfer.  If this were broken I would expect to see widespread
> > problems being reported.

> This is unfortunate naming I suppose. I reread the spi.h comments
> a few more times and it seems indeed, that .cs_change == 1 on last
> transfer means to a driver: "you may leave CS unchanged" - quite the
> reverse compared to non-last transfers.

cs_change also means that we should add an extra chip select transition
on transfers other than the last.

> Please drop this patch then.

OK.

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