linux-kernel - Re: [PATCH 1/3] gpiolib: don't use gpiochip_get

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Message-ID: <Z73EIu0AqnfPU33k@smile.fi.intel.com>
Date: Tue, 25 Feb 2025 15:22:42 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Linus Walleij <linus.walleij@...aro.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH 1/3] gpiolib: don't use gpiochip_get_direction() when
 registering a chip

On Tue, Feb 25, 2025 at 12:56:23PM +0100, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> 
> During chip registration we should neither check the return value of
> gc->get_direction() nor hold the SRCU lock when calling it. The former
> is because pin controllers may have pins set to alternate functions and
> return errors from their get_direction() callbacks. That's alright - we
> should default to the safe INPUT state and not bail-out. The latter is
> not needed because we haven't registered the chip yet so there's nothing
> to protect against dynamic removal. In fact: we currently hit a lockdep
> splat. Revert to calling the gc->get_direction() callback directly not
> not checking its value.

...

I think the below code deserves a commit (as a summary of the above commit
message).

> +		if (gc->get_direction && gpiochip_line_is_valid(gc, desc_index))
> +			assign_bit(FLAG_IS_OUT, &desc->flags,
> +				   !gc->get_direction(gc, desc_index));
> +		else
>  			assign_bit(FLAG_IS_OUT,
>  				   &desc->flags, !gc->direction_input);

Otherwise LGTM,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

-- 
With Best Regards,
Andy Shevchenko