linux-kernel - Re: [PATCH v2] p54: Fix an error handling path in p54spi

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Date:   Wed, 15 Jun 2022 23:03:34 +0200
From:   Christian Lamparter <chunkeey@...il.com>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     Kalle Valo <kvalo@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "John W. Linville" <linville@...driver.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        kernel-janitors@...r.kernel.org,
        Christian Lamparter <chunkeey@....de>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        Netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH v2] p54: Fix an error handling path in p54spi_probe()

On 13/06/2022 22:57, Christophe JAILLET wrote:
> Le 13/06/2022 à 22:02, Christian Lamparter a écrit :
>> On Sun, Jun 12, 2022 at 11:12 PM Christophe JAILLET
>> <christophe.jaillet@...adoo.fr> wrote:
>>>
>>> If an error occurs after a successful call to p54spi_request_firmware(), it
>>> must be undone by a corresponding release_firmware() as already done in
>>> the error handling path of p54spi_request_firmware() and in the .remove()
>>> function.
>>>
>>> Add the missing call in the error handling path and remove it from
>>> p54spi_request_firmware() now that it is the responsibility of the caller
>>> to release the firmawre
>>
>> that last word hast a typo:  firmware. (maybe Kalle can fix this in post).
> 
> More or less the same typo twice in a row... _Embarrassed_
> 
>>
>>> Fixes: cd8d3d321285 ("p54spi: p54spi driver")
>>> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
>> Acked-by: Christian Lamparter <chunkeey@...il.com>
>> (Though, v1 was fine too.)
>>> ---
>>> v2: reduce diffstat and take advantage on the fact that release_firmware()
>>> checks for NULL
>>
>> Heh, ok ;) . Now that I see it,  the "ret = p54_parse_firmware(...); ... "
>> could have been replaced with "return p54_parse_firmware(dev, priv->firmware);"
>> so the p54spi.c could shrink another 5-6 lines.
>>
>> I think leaving p54spi_request_firmware() callee to deal with
>> releasing the firmware
>> in the error case as well is nicer because it gets rid of a "but in
>> this case" complexity.
> 
> 
> Take the one you consider being the best one.

well said!

> 
> If it deserves a v3 to axe some lines of code, 
> I can do it but, as said previously,
> v1 is for me the cleaner and more future proof.

Gee, that last sentence about "future proof" is daring.
I don't know what's up on the horizon. For my part, I've been devresing
parts of carl9170 and now thinking about it. Because the various
request_firmware*() functions could be a target for devres too.
A driver usually loads the firmware in .probe(). It stays around because
of .suspend()+.resume() and gets freed by .release().
With devresing up request_firmware(), that release_firmware() would be
rendered obsolete in all of p54* cases.

There must be something that I have missed? right?

It's because there's already an extensive list of managed interfaces:
<https://www.kernel.org/doc/html/latest/driver-api/driver-model/devres.html>
But the firmware_class is not on it. Does somebody know the presumably
"very good" reason why not? I can't believe that this hasn't been done yet.

Regards,
Christian