[PATCH V2] pinctrl: Don't create a pinctrl handle if no pinctrl entries exist

[PATCH V2] pinctrl: Don't create a pinctrl handle if no pinctrl entries exist

[Jon Hunter]

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@nvidia.com>
---

Changes since V1:
- Added of_node_put()

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 | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/pinctrl/devicetree.c b/drivers/pinctrl/devicetree.c
index fe04e748dfe4..54dad89fc9bf 100644
--- a/drivers/pinctrl/devicetree.c
+++ b/drivers/pinctrl/devicetree.c
@@ -195,8 +195,13 @@ 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) {
+				of_node_put(np);
+				return -ENODEV;
+			}
 			break;
+		}
 		list = prop->value;
 		size /= sizeof(*list);
 
-- 
2.1.4

Re: [PATCH V2] pinctrl: Don't create a pinctrl handle if no pinctrl entries exist

[Linus Walleij]

On Thu, Jun 16, 2016 at 5:27 PM, Jon Hunter <jonathanh@nvidia.com> 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@nvidia.com>

Patch applied (after adding OF to the subject)

It's a bit dangerous because it changes semantics but let's see
if we survive it.

> 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.

It's better like this, logically. I'm just worried that there may be
code in the tree that depend on the bind always getting a handle.

Yours,
Linus Walleij