Re: [PATCH v2 1/1] leds: pca9532: Add device tree binding

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On 11/04/2016 4:38 PM, Jacek Anaszewski wrote:
On 04/11/2016 08:23 AM, Phil Reid wrote:
On 7/04/2016 10:02 PM, Jacek Anaszewski wrote:
Hi Phil,

Thanks for the update. Few more remarks below.

On 04/07/2016 09:22 AM, Phil Reid wrote:
This patch adds basic device tree support for the pca9532 LEDs.

Signed-off-by: Phil Reid <preid@xxxxxxxxxxxxxxxxx>
---
  .../devicetree/bindings/leds/leds-pca9532.txt      | 42 +++++++++++++
  drivers/leds/leds-pca9532.c                        | 69
++++++++++++++++++++--
  include/dt-bindings/leds/leds-pca9532.h            | 23 ++++++++
  include/linux/leds-pca9532.h                       | 18 ++----
  4 files changed, 135 insertions(+), 17 deletions(-)
  create mode 100644
Documentation/devicetree/bindings/leds/leds-pca9532.txt
  create mode 100644 include/dt-bindings/leds/leds-pca9532.h

diff --git a/Documentation/devicetree/bindings/leds/leds-pca9532.txt
b/Documentation/devicetree/bindings/leds/leds-pca9532.txt
new file mode 100644
index 0000000..284b96c
--- /dev/null
+++ b/Documentation/devicetree/bindings/leds/leds-pca9532.txt
@@ -0,0 +1,42 @@
+*NXP - pca9532 PWM LED Driver
+
+The PCA9532 family is SMBus I/O expander optimized for dimming LEDs.
+The PWM support 256 steps.
+
+Required properties:
+    - compatible:
+        "nxp,pca9530"
+        "nxp,pca9531"
+        "nxp,pca9532"
+        "nxp,pca9533"
+    - reg -  I2C slave address
+
+Each led is represented as a sub-node of the nxp,pca9530.
+
+Optional sub-node properties:
+    - label: Name for this LED. If omitted, the label is taken from
the node name.

Please also add a reference to common led bindings, as this property is
documented there:
"(see Documentation/devicetree/bindings/leds/common.txt):"
done.


+    - type: Output configuration, see
dt-bindings/leds/leds-pca9532.h (default NONE)
+    - state: Initial LED state (default OFF)

We already have "default-on" trigger for this purpose.
Not sure it does exactly the same thing.
This setting also associates a led with a particular PWM controller.
The chip has 2 shared PWM that each led can be controlled by.

default-on trigger sets the LED to max_brightness on init.
As I see pca9532_set_brightness() sets PCA9532_ON state if
passed LED_FULL and uses PCA9532_PWM0 for other values
greater than zero.

So, maybe it would make more sense if we used default-on trigger to
initialize LED to LED_FULL on init, but provide another DT property
'default-pwm' to determine which PWM block should be used by default?
Currently I see that driver uses only PWM0:

led->state = PCA9532_PWM0; /* Thecus: hardcode one pwm */

Alternatively the driver could expose a dedicated sysfs attribute
for changing the default pwm. This is of course out of this patch
scope.

I'll drop the state bit for this patch.
I ideally need to have the 2 PWMs controlling the LEDs but it's
going to take a bit more work.

--
Regards
Phil Reid


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