linux-kernel - Re: [PATCH 2/2] ASoC: DA7219: Implement error check on reg read and write

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Message-ID: <20181205112832.GA6205@sirena.org.uk>
Date:   Wed, 5 Dec 2018 11:28:32 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Adam Thomson <Adam.Thomson.Opensource@...semi.com>
Cc:     "Agrawal, Akshu" <Akshu.Agrawal@....com>,
        "djkurtz@...omium.org" <djkurtz@...omium.org>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        Support Opensource <Support.Opensource@...semi.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        "moderated list:SOUND - SOC LAYER / DYNAMIC AUDIO POWER MANAGEM..." 
        <alsa-devel@...a-project.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] ASoC: DA7219: Implement error check on reg read and
 write

On Wed, Dec 05, 2018 at 10:21:04AM +0000, Adam Thomson wrote:

> If the previous I2C access failed, how can we be sure that the write back to HW
> of 0xFF even succeeds? More importantly these error returns won't necessarily
> stop subsequent calls to controls within the Codec I believe, so you could still
> see unwanted writes to HW via I2C, if I2C is sporadically operational. Again I
> don't see this update resolving that. The key thing is to resolve why even just
> one I2C transaction fails.

Right, it's just not clear what we can constructively do if the I2C bus
falls to bits other than log things and the I2C controllers will
generally do that themselves.  There's no guarantee what made it
through to the device or what will in future make it through to the
device.

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