linux-kernel - Re: [PATCH 0/2] iio: Use __cleanup for a few ROHM sensors

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Message-ID: <37bba4fa-34c6-4b7c-ae65-75929213a8f2@gmail.com>
Date: Fri, 22 Nov 2024 08:10:08 +0200
From: Matti Vaittinen <mazziesaccount@...il.com>
To: Javier Carrasco <javier.carrasco.cruz@...il.com>,
 Matti Vaittinen <matti.vaittinen@...rohmeurope.com>
Cc: Jonathan Cameron <jic23@...nel.org>, Lars-Peter Clausen
 <lars@...afoo.de>, linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] iio: Use __cleanup for a few ROHM sensors

Hi Javier,

On 21/11/2024 15:54, Javier Carrasco wrote:
> On 21/11/2024 14:04, Matti Vaittinen wrote:
>> Use __cleanup.
>>
>> The series converts the rest of the ROHM sensors (maintained by me) to
>> use guard(mutex). This simplifies the error paths.
>>
>> As a note, kx022a accelerometer driver is handled in another series,
>> which also adds support for two new accelerometers. I did also patch the
>> driver for the BU27008 and BU27010 - but when I was testing the changes
>> I found that the BU27008 status is set to "obsolete". I'll try to dig
>> some information about the BU27010 and decide if having the driver
>> in-tree is still worth the effort, or if I should just send out patches
>> to drop it all. Hence patch to rohm-bu27008.c is not included in the
>> series. If someone is actually using the BU27008 or BU27010 and wants
>> to patch it - feel free to pick
>> 131315de97ff ("iio: bu27008: simplify using guard(mutex)")
>> from
>> https://github.com/M-Vaittinen/linux/tree/bu27008-cleanup
>>
>> ---
>>
>> Matti Vaittinen (2):
>>    iio: bu27034: simplify using guard(mutex)
>>    iio: bm1390: simplify using guard(mutex)
>>
>>   drivers/iio/light/rohm-bu27034.c   | 73 ++++++++++------------------
>>   drivers/iio/pressure/rohm-bm1390.c | 78 ++++++++++++------------------
>>   2 files changed, 55 insertions(+), 96 deletions(-)
>>
>>
>> base-commit: adc218676eef25575469234709c2d87185ca223a
> 
> Hi Matti,
> 
> Both patches look good to me, but I noticed that you kept a few
> mutex_lock() + mutex_unlock() in both drivers, in particular in the
> cases where a scoped_guard() could simplify the code. Did you leave
> those cases untouched on purpose?

Thanks for taking a look at the patches. Much appreciated :)

I remember leaving couple of direct calls to mutex_lock() and 
mutex_unlock() - but I think I left them only to places where I saw no 
real improvement by the use of guard() or scoped_guard(). It is likely I 
considered the locking in these cases being trivial. (Probably only for 
a duration of one or couple of function calls, with no error handling 
when a lock is held). The direct mutex_lock()/mutex_unlock() has no real 
room for usual errors (like leaving the function while lock was taken) 
in such case.

For me,

mutex_lock();
ret = foo();
mutex_unlock();

is as clear as it gets. I don't think scoped_guard() has benefits there. 
On the contrary, for me the scoped_guard() would be more complex and 
less obvious :)

Yours,
	-- Matti