linux-kernel - Re: [PATCH 2/5] powerpc: 83xx/gpio: use new line value setter callbacks

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Message-ID: <11e1a1e7-7bd3-4d48-804c-45b53b5e15d5@csgroup.eu>
Date: Wed, 30 Apr 2025 19:47:17 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Madhavan Srinivasan <maddy@...ux.ibm.com>,
 Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>,
 Naveen N Rao <naveen@...nel.org>, Linus Walleij <linus.walleij@...aro.org>,
 Anatolij Gustschin <agust@...x.de>, linuxppc-dev@...ts.ozlabs.org,
 linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
 Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH 2/5] powerpc: 83xx/gpio: use new line value setter
 callbacks



Le 30/04/2025 à 19:37, Bartosz Golaszewski a écrit :
> On Wed, Apr 30, 2025 at 7:33 PM Christophe Leroy
> <christophe.leroy@...roup.eu> wrote:
>>
>>
>>
>> Le 08/04/2025 à 09:21, Bartosz Golaszewski a écrit :
>>> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>>>
>>> struct gpio_chip now has callbacks for setting line values that return
>>> an integer, allowing to indicate failures. Convert the driver to using
>>> them.
>>>
>>> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>>> ---
>>>    arch/powerpc/platforms/83xx/mcu_mpc8349emitx.c | 6 ++++--
>>>    1 file changed, 4 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/arch/powerpc/platforms/83xx/mcu_mpc8349emitx.c b/arch/powerpc/platforms/83xx/mcu_mpc8349emitx.c
>>> index 4d8fa9ed1a67..d4ba6dbb86b2 100644
>>> --- a/arch/powerpc/platforms/83xx/mcu_mpc8349emitx.c
>>> +++ b/arch/powerpc/platforms/83xx/mcu_mpc8349emitx.c
>>> @@ -92,7 +92,7 @@ static void mcu_power_off(void)
>>>        mutex_unlock(&mcu->lock);
>>>    }
>>>
>>> -static void mcu_gpio_set(struct gpio_chip *gc, unsigned int gpio, int val)
>>> +static int mcu_gpio_set(struct gpio_chip *gc, unsigned int gpio, int val)
>>>    {
>>>        struct mcu *mcu = gpiochip_get_data(gc);
>>>        u8 bit = 1 << (4 + gpio);
>>> @@ -105,6 +105,8 @@ static void mcu_gpio_set(struct gpio_chip *gc, unsigned int gpio, int val)
>>>
>>>        i2c_smbus_write_byte_data(mcu->client, MCU_REG_CTRL, mcu->reg_ctrl);
>>>        mutex_unlock(&mcu->lock);
>>> +
>>> +     return 0;
>>
>> i2c_smbus_write_byte_data() can fail, why not return the value returned
>> by i2c_smbus_write_byte_data() ?
>>
> 
> The calls to i2c_smbus_write_byte_data() in this driver are
> universally not checked. I cannot test it and wasn't sure if that's on
> purpose so I decided to stay safe. Someone who has access to this
> platform could potentially fix it across the file.

As far as I can see this function is called three times in this file.

First time is in mcu_power_off(), which must return void.
Second time is inside a forever loop in shutdown_thread_fn(), and I 
can't see what could be done with the returned value.

Last time is in the function you are changing. Wouldn't it make sense to 
take the value into account here ? IIUC it is the purpose of the change, 
isn't it ?

Christophe