linux-kernel - Re: [PATCH 3/7] iio: adc: ad7793: claim direct mode when writing frequency

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Date:	Sun, 29 May 2016 19:33:58 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	Daniel Baluta <daniel.baluta@...il.com>,
	Alison Schofield <amsfield22@...il.com>
Cc:	Lars-Peter Clausen <lars@...afoo.de>,
	"Hennerich, Michael" <Michael.Hennerich@...log.com>,
	Hartmut Knaack <knaack.h@....de>,
	Peter Meerwald-Stadler <pmeerw@...erw.net>,
	"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/7] iio: adc: ad7793: claim direct mode when writing
 frequency

On 25/05/16 11:36, Daniel Baluta wrote:
> On Tue, May 24, 2016 at 10:17 PM, Alison Schofield <amsfield22@...il.com> wrote:
>> Driver was checking for direct mode and trying to lock it, but
>> left a gap where mode could change before the desired operation.
>> Use iio_device_claim_direct_mode() to guarantee device stays in
>> direct mode.
>>
>> Signed-off-by: Alison Schofield <amsfield22@...il.com>
>> Cc: Daniel Baluta <daniel.baluta@...il.com>
> 
> Acked-by: Daniel Baluta <daniel.baluta@...il.com>
Again, this one is not quite so trivial so I'll wait for Lars to take a look
even though I'm happy with it.

Thanks,

Jonathan
> 
>> ---
>>  drivers/iio/adc/ad7793.c | 13 ++++---------
>>  1 file changed, 4 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/iio/adc/ad7793.c b/drivers/iio/adc/ad7793.c
>> index 7b07bb6..3f41cd8 100644
>> --- a/drivers/iio/adc/ad7793.c
>> +++ b/drivers/iio/adc/ad7793.c
>> @@ -369,13 +369,6 @@ static ssize_t ad7793_write_frequency(struct device *dev,
>>         long lval;
>>         int i, ret;
>>
>> -       mutex_lock(&indio_dev->mlock);
>> -       if (iio_buffer_enabled(indio_dev)) {
>> -               mutex_unlock(&indio_dev->mlock);
>> -               return -EBUSY;
>> -       }
>> -       mutex_unlock(&indio_dev->mlock);
>> -
>>         ret = kstrtol(buf, 10, &lval);
>>         if (ret)
>>                 return ret;
>> @@ -387,12 +380,14 @@ static ssize_t ad7793_write_frequency(struct device *dev,
>>
>>         for (i = 0; i < 16; i++)
>>                 if (lval == st->chip_info->sample_freq_avail[i]) {
>> -                       mutex_lock(&indio_dev->mlock);
>> +                       ret = iio_device_claim_direct_mode(indio_dev);
>> +                       if (ret)
>> +                               return ret;
>>                         st->mode &= ~AD7793_MODE_RATE(-1);
>>                         st->mode |= AD7793_MODE_RATE(i);
>>                         ad_sd_write_reg(&st->sd, AD7793_REG_MODE,
>>                                          sizeof(st->mode), st->mode);
>> -                       mutex_unlock(&indio_dev->mlock);
>> +                       iio_device_release_direct_mode(indio_dev);
>>                         ret = 0;
>>                 }
>>
>> --
> --
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