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

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Message-ID: <0c94d0fc-dc0c-4e35-a6c1-2d7e01a3eb43@alliedtelesis.co.nz>
Date: Mon, 30 Sep 2024 09:17:34 +1300
From: Chris Packham <chris.packham@...iedtelesis.co.nz>
To: Markus Elfring <Markus.Elfring@....de>, 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>
Subject: Re: [PATCH v5 6/6] i2c: Add driver for the RTL9300 I2C controller

Hi Markus,

On 29/09/24 21:45, Markus Elfring wrote:
> …
>> +++ 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/ but I can see enough examples 
(although notably none in drivers/i2c) that I _think_ I can see how I 
could use it.