linux-kernel - Re: [PATCH 3/4] mmc: sdhci: defer probing on regulator_get

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Date:	Tue, 15 Apr 2014 12:28:45 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Andrew Bresticker <abrestic@...omium.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Chris Ball <chris@...ntf.net>,
	Ulf Hansson <ulf.hansson@...aro.org>
CC:	linux-mmc@...r.kernel.org, linux-tegra@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] mmc: sdhci: defer probing on regulator_get_optional()
 failures

On 04/14/2014 07:42 PM, Andrew Bresticker wrote:
> If regulator_get_optional() returns EPROBE_DEFER, it indicates
> that the regulator may show up later (e.g. the DT property is
> present but the corresponding regulator may not have probed).
> Instead of continuing without the regulator, return EPROBE_DEFER
> from sdhci_add_host().  Also, fix regulator leaks in the error
> paths in sdhci_add_host().

> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c

>  	if (IS_ERR_OR_NULL(host->vqmmc)) {

This is a pre-existing condition, but ick: Why doesn't this test either
IS_ERR() /or/ == NULL, but not both. On error, the regulator API should
either return and error-point or return NULL, so that client code
shouldn't need to check for both.

> +put_vmmc:
> +	if (host->vmmc)
> +		regulator_put(host->vmmc);
> +put_vqmmc:
> +	if (host->vqmmc)
> +		regulator_put(host->vqmmc);

If IS_ERR_OR_NULL() really is required above, it should be used here
too. More likely, I hope you need to replace if (host->vmmc) with if
(!IS_ERR(host->vmmc)).

I wonder if fixing this would help solve the crashes that Alex saw?
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