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

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Message-ID: <CAMRc=McOxP5j=HTm6xybdr_09X-khHcanz4chfEwa-m6y1+gZQ@mail.gmail.com>
Date: Wed, 30 Apr 2025 19:48:19 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Christophe Leroy <christophe.leroy@...roup.eu>
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

On Wed, Apr 30, 2025 at 7:47 PM Christophe Leroy
<christophe.leroy@...roup.eu> wrote:
>
>
>
> 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
>

Sure, I can do it. The purpose is first and foremost to convert all
drivers so that we can drop the old callbacks but I see what you mean.

Bart