Re: [PATCH 2/7] iio: adc: ad7791: claim direct mode when writing frequency

From: Lars-Peter Clausen
Date: Tue May 31 2016 - 09:20:34 EST

On 05/29/2016 07:06 PM, Jonathan Cameron wrote:
> On 25/05/16 11:34, Daniel Baluta wrote:
>> On Tue, May 24, 2016 at 10:16 PM, Alison Schofield <amsfield22@xxxxxxxxx> 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@xxxxxxxxx>
>>> Cc: Daniel Baluta <daniel.baluta@xxxxxxxxx>
>> Looks good to me. We could use an Acked-by from Lars here.
>> Acked-by: Daniel Baluta <daniel.baluta@xxxxxxxxx>
> 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.

It will only be locked once. sysfs_streq() will only match for a single
item. But you are right the code could be refactored to make that more
clearer. First run the lookup look and then apply afterwards.