linux-kernel - Re: [PATCH v2 2/3] phy: phy-rockchip-inno-usb2: Handle failed extcon allocation better

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Message-ID: <a34cbce8633fda9ed805adde3eeb1467@manjaro.org>
Date: Wed, 21 Aug 2024 21:05:07 +0200
From: Dragan Simic <dsimic@...jaro.org>
To: Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc: linux-rockchip@...ts.infradead.org, linux-phy@...ts.infradead.org,
 vkoul@...nel.org, kishon@...nel.org, heiko@...ech.de,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] phy: phy-rockchip-inno-usb2: Handle failed extcon
 allocation better

Hello Christophe,

On 2024-08-21 13:17, Christophe JAILLET wrote:
> Le 21/08/2024 à 09:37, Dragan Simic a écrit :
>> Return the actual error code upon failure to allocate extcon device, 
>> instead
>> of hardcoding -ENOMEM.  Use dev_err_probe() to also log appropriate 
>> messages,
>> which is fine because the containing function is used in the probe 
>> path.
>> 
>> Helped-by: Heiko Stubner <heiko@...ech.de>
>> Signed-off-by: Dragan Simic <dsimic@...jaro.org>
>> ---
>>   drivers/phy/rockchip/phy-rockchip-inno-usb2.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/phy/rockchip/phy-rockchip-inno-usb2.c 
>> b/drivers/phy/rockchip/phy-rockchip-inno-usb2.c
>> index 113bfc717ff0..05af46dda11d 100644
>> --- a/drivers/phy/rockchip/phy-rockchip-inno-usb2.c
>> +++ b/drivers/phy/rockchip/phy-rockchip-inno-usb2.c
>> @@ -435,7 +435,8 @@ static int rockchip_usb2phy_extcon_register(struct 
>> rockchip_usb2phy *rphy)
>>   						rockchip_usb2phy_extcon_cable);
>>     		if (IS_ERR(edev))
>> -			return -ENOMEM;
>> +			return dev_err_probe(rphy->dev, PTR_ERR(edev),
>> +					     "failed to allocate extcon device\n");
> 
> Returning PTR_ERR(edev) may make sense, but I don't think that adding
> a dev_err_probe() really helps.
> 
> devm_extcon_dev_allocate() can only return -EINVAL if it 2nd argument
> is NULL. It is trivial to see that it can't happen here,
> rockchip_usb2phy_extcon_cable is a global variable.
> 
> in all other cases, it returns -ENOMEM because of a failed memory
> allocation. In this case, usually it is not needed to log anything
> because it is already loud enough.

True, using dev_err_probe() in this case is somewhat redundant,
but it falls under the "still fine to use" category, [1] because
the error code passed to dev_err_probe() is received from another
function that was invoked.

On the other hand, another patch in this series tries to be strict
in another direction, by not using dev_err_probe() where the error
code passed to it is basically hardcoded. [2]

I hope this makes sense.

[1] 
https://lore.kernel.org/linux-phy/cover.1724225528.git.dsimic@manjaro.org/T/#mc3af7d24e31ed885732e6f26ca0d107b157d478b
[2] 
https://lore.kernel.org/linux-phy/cover.1724225528.git.dsimic@manjaro.org/T/#ma26b614412787814dab7923987b8c814f7e86beb

>>     		ret = devm_extcon_dev_register(rphy->dev, edev);
>>   		if (ret) {
>> 
>>