linux-kernel - Re: [PATCH v1 4/8] gpio: acpi: Even more tighten up ACPI GPIO lookups

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Date:   Thu, 23 Mar 2017 13:12:41 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Alexandre Courbot <gnurou@...il.com>,
        linux-gpio@...r.kernel.org, Hans de Goede <hdegoede@...hat.com>,
        linux-kernel@...r.kernel.org,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        linux-acpi@...r.kernel.org, Irina Tirdea <irina.tirdea@...el.com>,
        Bastien Nocera <hadess@...ess.net>
Subject: Re: [PATCH v1 4/8] gpio: acpi: Even more tighten up ACPI GPIO lookups

On Thu, Mar 23, 2017 at 09:46:14PM +0200, Andy Shevchenko wrote:
> The commit 10cf4899f8af ("gpiolib: tighten up ACPI legacy gpio lookups")
> prevents to getting same resource twice if the driver asks twice using same

s/same/different/

> connection ID.
> 
> But the whole idea of fallback might bring some problems. Imagine the case when
> we have two versions of BIOS/hardware where in one _DSD is introduced along
> with GPIO resources, but the other one uses just plain GPIO resource for
> another purpose
> 
> Case 1:
> 
>     Device (DEVX)
>     {
>         ...
>         Name (_CRS, ResourceTemplate ()
>         {
>             GpioIo (Exclusive, PullUp, 0, 0, IoRestrictionInputOnly,
>                     "\\_SB.GPO0", 0, ResourceConsumer) {15}
>         })
>         Name (_DSD, Package ()
>         {
>             ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
>             Package ()
>             {
>                 Package () {"some-gpios", Package() {^DEVX, 0, 0, 0 }},
>             }
>         })
>     }
> 
> Case 2:
> 
>     Device (DEVX)
>     {
>         ...
>         Name (_CRS, ResourceTemplate ()
>         {
>             GpioIo (Exclusive, PullUp, 0, 0, IoRestrictionInputOnly,
>                     "\\_SB.GPO0", 0, ResourceConsumer) {27}
>         })
>     }
> 
> To prevent the possible misconfiguration tighten up even more ACPI GPIO lookups
> for case without connection ID provided.

I wonder if this will break Goodix. Irina, Bastien?

> 
> In the past the issue had been triggered by "use mctrl_gpio helpers" series
> [1,2].
> 
> Besides above, removal of the main logic of acpi_can_fallback_to_crs()
> eliminates a potential memory leak when the same device has been unbound and
> bound again.

Where? We'll reuse lookup table as ACPI device is still the same.

> 
> [1] commit 4ef03d328769 ("tty/serial/8250: use mctrl_gpio helpers")
> [2] https://patchwork.kernel.org/patch/9283745/
> 
> Cc: Dmitry Torokhov <dmitry.torokhov@...il.com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  drivers/gpio/gpiolib-acpi.c | 36 +-----------------------------------
>  1 file changed, 1 insertion(+), 35 deletions(-)
> 
> diff --git a/drivers/gpio/gpiolib-acpi.c b/drivers/gpio/gpiolib-acpi.c
> index 21e4930ca2db..e516b7a0cc50 100644
> --- a/drivers/gpio/gpiolib-acpi.c
> +++ b/drivers/gpio/gpiolib-acpi.c
> @@ -1121,45 +1121,11 @@ int acpi_gpio_count(struct device *dev, const char *con_id)
>  	return count ? count : -ENOENT;
>  }
>  
> -struct acpi_crs_lookup {
> -	struct list_head node;
> -	struct acpi_device *adev;
> -	const char *con_id;
> -};
> -
> -static DEFINE_MUTEX(acpi_crs_lookup_lock);
> -static LIST_HEAD(acpi_crs_lookup_list);
> -
>  bool acpi_can_fallback_to_crs(struct acpi_device *adev, const char *con_id)
>  {
> -	struct acpi_crs_lookup *l, *lookup = NULL;
> -
>  	/* Never allow fallback if the device has properties */
>  	if (adev->data.properties || adev->driver_gpios)
>  		return false;
>  
> -	mutex_lock(&acpi_crs_lookup_lock);
> -
> -	list_for_each_entry(l, &acpi_crs_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 = kstrdup(con_id, GFP_KERNEL);
> -			list_add_tail(&lookup->node, &acpi_crs_lookup_list);
> -		}
> -	}
> -
> -	mutex_unlock(&acpi_crs_lookup_lock);
> -
> -	return lookup &&
> -		((!lookup->con_id && !con_id) ||
> -		 (lookup->con_id && con_id &&
> -		  strcmp(lookup->con_id, con_id) == 0));
> +	return con_id == NULL;
>  }
> -- 
> 2.11.0
> 

-- 
Dmitry