Re: [PATCH v3 3/4] pinctrl: Implementation of the generic scmi-pinctrl driver

From: Oleksii Moisieiev <Oleksii_Moisieiev@epam.com>
To: "andy.shevchenko@gmail.com" <andy.shevchenko@gmail.com>
Cc: "sudeep.holla@arm.com" <sudeep.holla@arm.com>,
	Cristian Marussi <cristian.marussi@arm.com>,
	Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Linus Walleij <linus.walleij@linaro.org>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>
Subject: Re: [PATCH v3 3/4] pinctrl: Implementation of the generic scmi-pinctrl driver
Date: Thu, 20 Jul 2023 13:40:03 +0000	[thread overview]
Message-ID: <87sf9ihfc7.fsf@epam.com> (raw)
In-Reply-To: <ZIAxLdexyKBnMOmU@surfacebook>

Hi Andy,

andy.shevchenko@gmail.com writes:

> Tue, Jun 06, 2023 at 04:22:28PM +0000, Oleksii Moisieiev kirjoitti:
>> scmi-pinctrl driver implements pinctrl driver interface and using
>> SCMI protocol to redirect messages from pinctrl subsystem SDK to
>> SCP firmware, which does the changes in HW.
>> 
>> This setup expects SCP firmware (or similar system, such as ATF)
>> to be installed on the platform, which implements pinctrl driver
>> for the specific platform.
>> 
>> SCMI-Pinctrl driver should be configured from the device-tree and uses
>> generic device-tree mappings for the configuration.

[snip]

> ...
>
>> +error:
>
> Labels shoud be self-explanatory, i.e. they should tell what _will_ be when goto.
>
>> +	devm_kfree(pmx->dev, pmx->functions[selector].groups);
>
> Red Flag. Please, elaborate.
>

Thank you for the review.
I did some research regarding this and now I'm confused. Could you
please explain to me why it's a red flag?
IIUC devm_alloc/free functions are the calls to the resource-managed
alloc/free command, which is bound to the device.
pinctrl-scmi driver does devm_pinctrl_register_and_init which does
devres_alloc and doesn't open devres_group like
scmi_alloc_init_protocol_instance (thanks to Cristian detailed
explanation).

As was mentioned in Documentation/driver-api/driver-model/devres.rst:

```
No matter what, all devres entries are released on driver detach.  On
release, the associated release function is invoked and then the
devres entry is freed.
```

Also there is devm_pinctrl_get call listed in the managed interfaces.

My understanding is that all resources, bound to the particular device
will be freed on driver detach.

Also I found some examples of using devm_alloc/free like from dt_node_to_map
call in pinctrl-simple.c driver.

I agree that I need to implement .remove callback with proper cleanup,
but why can't I use devm_* here?
Maybe I've misunderstood your point.

-- 
Thanks,
Oleksii