linux-kernel - Re: [PATCH] gpio: nomadik: Add check for clk

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Message-Id: <D9694O0MKV31.3SY6ZCTSKXWI9@bootlin.com>
Date: Mon, 14 Apr 2025 11:24:51 +0200
From: Théo Lebrun <theo.lebrun@...tlin.com>
To: "Chenyuan Yang" <chenyuan0y@...il.com>, <linus.walleij@...aro.org>,
 <brgl@...ev.pl>
Cc: <linux-arm-kernel@...ts.infradead.org>, <linux-gpio@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gpio: nomadik: Add check for clk_enable()

Hello Chenyuan, Linus, Bartosz,

On Sat Apr 12, 2025 at 9:31 PM CEST, Chenyuan Yang wrote:
> Add check for the return value of clk_enable() to catch
> the potential error.
>
> This is similar to the commit 8332e6670997
> ("spi: zynq-qspi: Add check for clk_enable()").
>
> Signed-off-by: Chenyuan Yang <chenyuan0y@...il.com>
> Fixes: 966942ae4936 ("gpio: nomadik: extract GPIO platform driver from drivers/pinctrl/nomadik/")
> ---
>  drivers/gpio/gpio-nomadik.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpio/gpio-nomadik.c b/drivers/gpio/gpio-nomadik.c
> index fa19a44943fd..dbc4cdddf4df 100644
> --- a/drivers/gpio/gpio-nomadik.c
> +++ b/drivers/gpio/gpio-nomadik.c
> @@ -262,8 +262,11 @@ static unsigned int nmk_gpio_irq_startup(struct irq_data *d)
>  {
>  	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
>  	struct nmk_gpio_chip *nmk_chip = gpiochip_get_data(gc);
> +	int ret;
>  
> -	clk_enable(nmk_chip->clk);
> +	ret = clk_enable(nmk_chip->clk);
> +	if (ret)
> +		return ret;
>  	nmk_gpio_irq_unmask(d);
>  	return 0;
>  }

Returning a negative value whereas the ->irq_startup() [0] return value
is an unsigned int? From some quick godbolt testing and briefly reading
the spec it looks safe to do a round trip (signed->unsigned->signed),
though not ideal to my eyes.

The caller is __irq_startup() [1].

As for why irq_startup returns an unsigned int, I am unsure. The kernel
Git history isn't enough to know more. The startup field in struct
hw_interrupt_type appeared on v2.3.14 [2], so no commit message to
explain decisions.

Seeing the __irq_startup() code, my proposal would be to turn the return
value to a signed int, but I haven't exhaustively checked codepaths.

Thanks,

[0]: https://elixir.bootlin.com/linux/v6.13.7/source/include/linux/irq.h#L503
[1]: https://elixir.bootlin.com/linux/v6.13.7/source/kernel/irq/chip.c#L244
[2]: https://elixir.bootlin.com/linux/2.3.14/source/include/linux/irq.h#L21

--
Théo Lebrun, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com