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SubjectRe: [PATCH 2/7] iio: adc: ad7791: claim direct mode when writing frequency
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On 29/05/16 18:06, Jonathan Cameron wrote:
> On 25/05/16 11:34, Daniel Baluta wrote:
>> On Tue, May 24, 2016 at 10:16 PM, Alison Schofield <amsfield22@gmail.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@gmail.com>
>>> Cc: Daniel Baluta <daniel.baluta@gmail.com>
>>
>> Looks good to me. We could use an Acked-by from Lars here.
>>
>> Acked-by: Daniel Baluta <daniel.baluta@gmail.com>
> This one is a little more interesting. I wonder if we wouldn't be better
> off taking the lock for the whole function rather than dropping it for
> short periods.
>
> Can apply such a change at a later date however.
>
> Applied to the togreg branch of iio.git - initially pushed out as testing
> for the autobuilders to play with it.
Actually haven't seen Daniel suggesting an Ack from Lars might be good for this
one I've backed it out for now.

Lars?
>
> Thanks,
>
> Jonathan
>
>>
>>> ---
>>> drivers/iio/adc/ad7791.c | 15 ++++-----------
>>> 1 file changed, 4 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/drivers/iio/adc/ad7791.c b/drivers/iio/adc/ad7791.c
>>> index cf172d58..f7edacc 100644
>>> --- a/drivers/iio/adc/ad7791.c
>>> +++ b/drivers/iio/adc/ad7791.c
>>> @@ -272,24 +272,17 @@ static ssize_t ad7791_write_frequency(struct device *dev,
>>> struct ad7791_state *st = iio_priv(indio_dev);
>>> 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 = -EINVAL;
>>> -
>>> for (i = 0; i < ARRAY_SIZE(ad7791_sample_freq_avail); i++) {
>>> if (sysfs_streq(ad7791_sample_freq_avail[i], buf)) {
>>>
>>> - mutex_lock(&indio_dev->mlock);
>>> + ret = iio_device_claim_direct_mode(indio_dev);
>>> + if (ret)
>>> + return ret;
>>> st->filter &= ~AD7791_FILTER_RATE_MASK;
>>> st->filter |= i;
>>> ad_sd_write_reg(&st->sd, AD7791_REG_FILTER,
>>> sizeof(st->filter), st->filter);
>>> - mutex_unlock(&indio_dev->mlock);
>>> + iio_device_release_direct_mode(indio_dev);
>>> ret = 0;
>>> break;
>>> }
>>> --
>>> 2.1.4
>>>
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