linux-kernel - Re: [PATCH 3/4] mmc: mmci: Ensure return value of regulator

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Date:	Fri, 3 May 2013 10:20:10 +0200
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Lee Jones <lee.jones@...aro.org>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	arnd@...db.de, linus.walleij@...ricsson.com,
	srinidhi.kasagar@...ricsson.com,
	Russell King <linux@....linux.org.uk>,
	Chris Ball <cjb@...top.org>
Subject: Re: [PATCH 3/4] mmc: mmci: Ensure return value of regulator_enable()
 is checked

On 3 May 2013 10:16, Lee Jones <lee.jones@...aro.org> wrote:
> On Fri, 03 May 2013, Ulf Hansson wrote:
>
>> On 2 May 2013 17:48, Lee Jones <lee.jones@...aro.org> wrote:
>> > This patch suppresses the warning below:
>> >
>> > drivers/mmc/host/mmci.c: In function ‘mmci_set_ios’:
>> > drivers/mmc/host/mmci.c:1165:20: warning: ignoring return value of
>> >         ‘regulator_enable’, declared with attribute warn_unused_result
>> >         [-Wunused-result]
>> >
>> > Cc: Russell King <linux@....linux.org.uk>
>> > Cc: Chris Ball <cjb@...top.org>
>> > Signed-off-by: Lee Jones <lee.jones@...aro.org>
>> > ---
>> >  drivers/mmc/host/mmci.c |    9 +++++++--
>> >  1 file changed, 7 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
>> > index 375c109..f4f3038 100644
>> > --- a/drivers/mmc/host/mmci.c
>> > +++ b/drivers/mmc/host/mmci.c
>> > @@ -1130,6 +1130,7 @@ static void mmci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
>> >         struct variant_data *variant = host->variant;
>> >         u32 pwr = 0;
>> >         unsigned long flags;
>> > +       int ret;
>> >
>> >         pm_runtime_get_sync(mmc_dev(mmc));
>> >
>> > @@ -1161,8 +1162,12 @@ static void mmci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
>> >                 break;
>> >         case MMC_POWER_ON:
>> >                 if (!IS_ERR(mmc->supply.vqmmc) &&
>> > -                   !regulator_is_enabled(mmc->supply.vqmmc))
>>
>> I realize that we actually have a bug here (and in the MMC_POWER_OFF
>> mode as well).
>>
>> We shall not use regulator_is_enabled API as a trigger to enable/fetch
>> a reference to the regulator, since it will only tell us if the
>> regulator is enabled - hw wise.
>> Instead we need a local variable in the mmci host struct keeping track
>> if we have enabled the regulator. Do you mind fix this up in this
>> patch as well since it is tightly coupled to the regulator handling!?
>
> IMHO I think that should be taken care of in a separate patch. This
> patch only touches the line containing regulator_is_enabled() to
> encompass a multi-line comparison result.
>
> Care to write that patch? I have so much on my TODO already. :|

Sure, I can fix it.

I guess this patch will be going through Russell's patch tracker?

>
>> Otherwise it looks good to me.
>>
>> Kind regards
>> Ulf Hansson
>>
>> > -                       regulator_enable(mmc->supply.vqmmc);
>> > +                   !regulator_is_enabled(mmc->supply.vqmmc)) {
>> > +                       ret = regulator_enable(mmc->supply.vqmmc);
>> > +                       if (ret < 0)
>> > +                               dev_err(mmc_dev(mmc),
>> > +                                       "failed to enable vqmmc regulator\n");
>> > +               }
>> >
>> >                 pwr |= MCI_PWR_ON;
>> >                 break;
>> >
>
> --
> Lee Jones
> Linaro ST-Ericsson Landing Team Lead
> Linaro.org │ Open source software for ARM SoCs
> Follow Linaro: Facebook | Twitter | Blog
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