linux-kernel - Re: [PATCH] pinctrl: Don't create a pinctrl handle if no pinctrl entries exist

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Date:	Thu, 16 Jun 2016 16:20:17 +0100
From:	Jon Hunter <jonathanh@...dia.com>
To:	Linus Walleij <linus.walleij@...aro.org>
CC:	<linux-gpio@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pinctrl: Don't create a pinctrl handle if no pinctrl
 entries exist


On 16/06/16 13:39, Jon Hunter wrote:
> When pinctrl_get() is called for a device, it will return a valid handle
> even if the device itself has no pinctrl state entries defined in
> device-tree. This is caused by the function pinctrl_dt_to_map() which
> will return success even if the first pinctrl state, 'pinctrl-0', is not
> found in the device-tree node for a device.
> 
> According to the pinctrl device-tree binding documentation, pinctrl
> states must be numbered starting from 0 and so 'pinctrl-0' should always
> be present if a device uses pinctrl and therefore, if 'pinctrl-0' is not
> present it seems valid that we should not return a valid pinctrl handle.
> 
> Fix this by returning an error code if the property 'pinctrl-0' is not
> present for a device.
> 
> Signed-off-by: Jon Hunter <jonathanh@...dia.com>
> ---
> 
> I was wondering if this meant we are creating pinctrl handles for
> devices on boot that don't use pinctrl (when
> calling pinctrl_bind_pins()). However, although devm_pinctrl_get()
> does return successful for all devices, the subsequent call to
> pinctrl_lookup_state() (to get the default state) will fail and so
> we will destroy the pinctrl handle afterall.
>
>  drivers/pinctrl/devicetree.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pinctrl/devicetree.c b/drivers/pinctrl/devicetree.c
> index fe04e748dfe4..f41c16e11a11 100644
> --- a/drivers/pinctrl/devicetree.c
> +++ b/drivers/pinctrl/devicetree.c
> @@ -195,8 +195,11 @@ int pinctrl_dt_to_map(struct pinctrl *p)
>  		propname = kasprintf(GFP_KERNEL, "pinctrl-%d", state);
>  		prop = of_find_property(np, propname, &size);
>  		kfree(propname);
> -		if (!prop)
> +		if (!prop) {
> +			if (state == 0)

I think there should be a of_node_put() here. Will resend.

> +				return -ENODEV;
>  			break;
> +		}

Cheers
Jon

-- 
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