linux-kernel - Re: [BUG] Kernel crash on Allwinner H3 due to sound core changes

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Message-ID: <20180302124050.GF6255@sirena.org.uk>
Date:   Fri, 2 Mar 2018 12:40:50 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Jernej Škrabec <jernej.skrabec@...l.net>
Cc:     kuninori.morimoto.gx@...esas.com, maxime.ripard@...e-electrons.com,
        wens@...e.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, alsa-devel@...a-project.org
Subject: Re: [BUG] Kernel crash on Allwinner H3 due to sound core changes

On Thu, Mar 01, 2018 at 11:23:57PM +0100, Jernej Škrabec wrote:

> I removed parts of the code from the sun4i codec driver and interestingly it 
> doesn't crash if I remove following lines:

> ret = devm_snd_dmaengine_pcm_register(&pdev->dev, NULL, 0);
> if (ret) {
> 	dev_err(&pdev->dev, "Failed to register against DMAEngine\n");
> 	goto err_assert_reset;
> }

> Is it possible that NULL pointer causes troubles somewhere down the line?

Shouldn't be, that's just the configuration which is optional and not
what we're crashing trying to register, we can mostly configure things
by querying the capabilities of the DMA controller via the dmaengine API
these days.  You're removing all the DMA support there so cutting out a
huge segment of the initialization of both this driver and the machine
driver.  Other sunxi devices seem to be starting happily in -next so
there's something system dependent here...

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