linux-kernel - Re: [PATCH v5 6/6] i2c: Add driver for the RTL9300 I2C controller

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Message-ID: <4eb3dbbb-d3fd-43f4-b90d-9ecc222a87f6@web.de>
Date: Mon, 30 Sep 2024 09:55:45 +0200
From: Markus Elfring <Markus.Elfring@....de>
To: Chris Packham <chris.packham@...iedtelesis.co.nz>,
 linux-i2c@...r.kernel.org, linux-pm@...r.kernel.org,
 linux-mips@...r.kernel.org, devicetree@...r.kernel.org,
 Andi Shyti <andi.shyti@...nel.org>, Conor Dooley <conor+dt@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Lee Jones <lee@...nel.org>,
 Rob Herring <robh@...nel.org>, Sebastian Reichel <sre@...nel.org>,
 Thomas Bogendörfer <tsbogend@...ha.franken.de>
Cc: LKML <linux-kernel@...r.kernel.org>, linux-doc@...r.kernel.org,
 kernel-janitors@...r.kernel.org,
 Javier Carrasco Cruz <javier.carrasco.cruz@...il.com>,
 Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v5 6/6] i2c: Add driver for the RTL9300 I2C controller

>> …
>>> +++ b/drivers/i2c/busses/i2c-rtl9300.c
>>> @@ -0,0 +1,422 @@
>> …
>>> +static int rtl9300_i2c_smbus_xfer(struct i2c_adapter *adap, u16 addr, unsigned short flags,
>>> +                  char read_write, u8 command, int size,
>>> +                  union i2c_smbus_data *data)
>>> +{
>> …
>>> +    mutex_lock(&i2c->lock);
>>> +    if (chan->sda_pin != i2c->sda_pin) {
>> …
>>> +out_unlock:
>>> +    mutex_unlock(&i2c->lock);
>>> +
>>> +    return ret;
>>> +}
>> …
>>
>> Under which circumstances would you become interested to apply a statement
>> like “guard(mutex)(&i2c->lock);”?
>> https://elixir.bootlin.com/linux/v6.11/source/include/linux/mutex.h#L196
>
> At this stage I don't what to change unless Andi insists that I do.
>
> I can't find much mention of using guard() on https://www.kernel.org/doc/html/latest/

Do you find any other information sources more encouraging?


> but I can see enough examples (although notably none in drivers/i2c) that I _think_ I can see how I could use it.

See also (for example):
Article “Linux Kernel Development - Automatic Cleanup”
by Javier Carrasco Cruz
2024-06-17
https://javiercarrascocruz.github.io/kernel-auto-cleanup-2#2-automatic-mutex-handling

Regards,
Markus