linux-kernel - Re: [PATCH v2] gpiolib: Show correct direction from the beginning

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Date:   Fri, 21 Sep 2018 07:25:14 -0500
From:   Timur Tabi <timur@...nel.org>
To:     Jeffrey Hugo <jhugo@...eaurora.org>
Cc:     Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>, swboyd@...omium.org,
        linux-gpio@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] gpiolib: Show correct direction from the beginning

Jeff, can you test these two patches on Amberwing to make sure that they 
don't cause an XPU violation on boot?

The call to gpiochip_line_is_valid() should return false on any GPIOs 
that aren't listed in the ACPI table.

My concern is that this patch might be calling gpiochip_line_is_valid() 
too early, before all the arrays have been set up.

Thanks.

On 9/21/18 5:36 AM, Ricardo Ribalda Delgado wrote:
> Current code assumes that the direction is input if direction_input
> function is set.
> This might not be the case on GPIOs with programmable direction.
> 
> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
> ---
>   drivers/gpio/gpiolib.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 4b45de883ada..00c17f64d9ff 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -1352,7 +1352,12 @@ int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data,
>   		 * it does, and in case chip->get_direction is not set, we may
>   		 * expose the wrong direction in sysfs.
>   		 */
> -		desc->flags = !chip->direction_input ? (1 << FLAG_IS_OUT) : 0;
> +		if (chip->get_direction && gpiochip_line_is_valid(chip, i))
> +			desc->flags = !chip->get_direction(chip, i) ?
> +					(1 << FLAG_IS_OUT) : 0;
> +		else
> +			desc->flags = !chip->direction_input ?
> +					(1 << FLAG_IS_OUT) : 0;
>   	}
>   
>   #ifdef CONFIG_PINCTRL
>