linux-kernel - Re: [PATCH v2 3/8] iio: accel: kx022a: Use cleanup.h helpers

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Message-ID: <bda7eaff-1315-46d0-83b4-a14060c2af1c@gmail.com>
Date: Mon, 25 Nov 2024 11:34:36 +0200
From: Matti Vaittinen <mazziesaccount@...il.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
 Lars-Peter Clausen <lars@...afoo.de>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, linux-iio@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/8] iio: accel: kx022a: Use cleanup.h helpers

Hello Jonathan,

Thanks again!

On 23/11/2024 18:42, Jonathan Cameron wrote:
> On Thu, 21 Nov 2024 10:20:23 +0200
> Matti Vaittinen <mazziesaccount@...il.com> wrote:
> 
>> A few functions in KX022A need to use mutex for protecting the
>> enabling/disabling of the measurement while configurations are being
>> made. Some of the functions can be slightly simplified by using the
>> __cleanup based scoped mutexes, which allows dropping the goto based
>> unlocking at error path.
>>
>> Simplify error paths using guard(mutex).
>>
>> Signed-off-by: Matti Vaittinen <mazziesaccount@...il.com>
> Now we have guard(), the main reason (I think) for the
> combined on + lock and off + unlock paths is gone. So can
> we just flatten those and do the locking at caller.

I did consider this too :)

Why I decided to keep it as it is, (even though we need the extra 
mutex_unlock() at certain error path) is because I kind of like the 
lock+off and unlock+on functions. This locking does not protect data, 
but really a sequence of operations that needs to be done while sensor 
is OFF state. It's almost like a doc saying that "please, ensure the 
sensor is OFF for the following operations" :)

(Another thing is that we do claim the direct mode in write_raw, and 
goto is still handy for releasing it. Scoped guards won't play nicely 
with goto. Yes, we could probably use the __cleanup for direct mode, but 
I still like the lock+off, unlock+on for the reason above)

Yours,
	-- Matti