linux-kernel - Re: [PATCH] gpiolib: tighten up ACPI legacy gpio lookups

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Date:	Fri, 6 Nov 2015 10:08:14 +0200
From:	Mika Westerberg <mika.westerberg@...ux.intel.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Johan Hovold <johan@...nel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	"Tirdea, Irina" <irina.tirdea@...el.com>,
	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] gpiolib: tighten up ACPI legacy gpio lookups

On Thu, Nov 05, 2015 at 11:38:38AM -0800, Dmitry Torokhov wrote:
> We should not fall back to the legacy unnamed gpio lookup style if the
> driver requests gpios with different names, because we'll give out the same
> gpio twice. Let's keep track of the names that were used for the device and
> only do the fallback for the first name used.
> 
> Also disable fallback to _CRS gpios if ACPI device has DT-like
> properties or driver-supplied gpio mappings.

Thanks for taking care of this!

> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> ---
> 
> This version incorporates changes suggested by Mika Westerberg in
> response to the draft patch I posted in Goodix thread.
> 
>  drivers/gpio/gpiolib.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 47 insertions(+)
> 
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index a18f00f..9631ee8 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -1841,6 +1841,50 @@ static struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id,
>  	return desc;
>  }
>  
> +struct acpi_gpio_lookup {
> +	struct list_head node;
> +	struct acpi_device *adev;
> +	const char *con_id;
> +};
> +
> +static DEFINE_MUTEX(acpi_gpio_lookup_lock);
> +static LIST_HEAD(acpi_gpio_lookup_list);
> +
> +static bool acpi_can_fallback_to_crs(struct acpi_device *adev,
> +				     const char *con_id)
> +{
> +	struct acpi_gpio_lookup *l, *lookup = NULL;
> +
> +	/* Never fallback if the device has properties */
> +	if (adev->data.properties || adev->driver_gpios)
> +		return false;

I missed the fact that struct acpi_device is declared in
<acpi/acpi_bus.h> so we can't use the two fields directly here when
!CONFIG_ACPI. Sorry about that.

Do you think we can just add 

#ifdef CONFIG_ACPI

#endif

around the above check?

Alternatively we could add an inline function to drivers/gpio/gpiolib.h
like:

#ifdef CONFIG_ACPI
static inline bool acpi_gpio_has_properties(struct acpi_device *adev)
{
	return adev->data.properties || adev->driver_gpios;
}
#else
static inline bool acpi_gpio_has_properties(struct acpi_device *adev)
{
	return false;
}
#endif

> +
> +	mutex_lock(&acpi_gpio_lookup_lock);
> +
> +	list_for_each_entry(l, &acpi_gpio_lookup_list, node) {
> +		if (l->adev == adev) {
> +			lookup = l;
> +			break;
> +		}
> +	}
> +
> +	if (!lookup) {
> +		lookup = kmalloc(sizeof(*lookup), GFP_KERNEL);
> +		if (lookup) {
> +			lookup->adev = adev;
> +			lookup->con_id = con_id;
> +			list_add_tail(&lookup->node, &acpi_gpio_lookup_list);
> +		}
> +	}
> +
> +	mutex_unlock(&acpi_gpio_lookup_lock);
> +
> +	return lookup &&
> +		((!lookup->con_id && !con_id) ||
> +		 (lookup->con_id && con_id &&
> +		  strcmp(lookup->con_id, con_id) == 0));
> +}
> +
>  static struct gpio_desc *acpi_find_gpio(struct device *dev, const char *con_id,
>  					unsigned int idx,
>  					enum gpio_lookup_flags *flags)
> @@ -1868,6 +1912,9 @@ static struct gpio_desc *acpi_find_gpio(struct device *dev, const char *con_id,
>  
>  	/* Then from plain _CRS GPIOs */
>  	if (IS_ERR(desc)) {
> +		if (!acpi_can_fallback_to_crs(adev, con_id))
> +			return ERR_PTR(-ENOENT);
> +
>  		desc = acpi_get_gpiod_by_index(adev, NULL, idx, &info);
>  		if (IS_ERR(desc))
>  			return desc;
> -- 
> 2.6.0.rc2.230.g3dd15c0
> 
> 
> -- 
> Dmitry
--
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