linux-kernel - Re: [PATCH v2 1/3] i2c: add init

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Message-ID: <27cc9ae5-1c13-4ec9-ab10-ae95d6339116@gmail.com>
Date: Wed, 13 Aug 2025 12:24:22 +0200
From: Gabor Juhos <j4g8y7@...il.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Wolfram Sang <wsa@...nel.org>,
 Wolfram Sang <wsa+renesas@...g-engineering.com>,
 Andi Shyti <andi.shyti@...nel.org>, Russell King
 <rmk+kernel@...linux.org.uk>, Andrew Lunn <andrew@...n.ch>,
 Hanna Hawa <hhhawa@...zon.com>, Robert Marko <robert.marko@...tura.hr>,
 Linus Walleij <linus.walleij@...aro.org>, linux-i2c@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Imre Kaloz <kaloz@...nwrt.org>, stable@...r.kernel.org
Subject: Re: [PATCH v2 1/3] i2c: add init_recovery() callback

2025. 08. 11. 22:17 keltezéssel, Andy Shevchenko írta:
> On Mon, Aug 11, 2025 at 09:49:55PM +0200, Gabor Juhos wrote:
>> Add a new init_recovery() callback to struct 'i2c_bus_recovery_info'
>> and modify the i2c_init_recovery() function to call that if specified
>> instead of the generic i2c_gpio_init_recovery() function.
>>
>> This allows controller drivers to skip calling the generic code by
>> implementing a dummy callback function, or alternatively to run a
>> fine tuned custom implementation.
>>
>> This is needed for the 'i2c-pxa' driver in order to be able to fix
>> a long standing bug for which the fix will be implemented in a
> 
>> followup patch.
> 
> "...next change."

Ok.

> 
> ...
> 
> The first traditional question is why the generic recovery is not working.


The details are in the driver specific patches. Should I write it all down here too?

> 
> ...
> 
>> -	if (i2c_gpio_init_recovery(adap) == -EPROBE_DEFER)
>> +	if (bri->init_recovery) {
>> +		ret = bri->init_recovery(adap);
>> +		if (ret)
>> +			return ret;
> 
>> +	} else if (i2c_gpio_init_recovery(adap) == -EPROBE_DEFER) {
>>  		return -EPROBE_DEFER;
>> +	}
> 
> If the above stays, I think we would drop the last and always have
> init_recovery to be assigned.
> 

In that case we would have something like this:

    if (!bri->init_recovery)
        bri->init_recovery = i2c_gpio_init_recovery;

    ret = bri->init_recovery(adap);
    if (ret)
        return ret;

Since the callback is used only once, and within the same fuction where it is
assigned, I don't really see the advantage of the assignment. Although it
definitely looks cleaner as far as error handling is concerned.

Originally, I have used the following solution:

    if (bri->init_recovery)
        ret = bri->init_recovery(adap);
    else
        ret = i2c_gpio_init_recovery(adap);

    if (ret)
        return ret;

However the existing code ignores errors from i2c_gpio_init_recovery() except
EPROBE_DEFER, so I changed this to the code proposed in the patch in order to
keep the existing behaviour.

Regards,
Gabor