Re: [PATCH 1/2] dt-bindings: hwmon: add binding documentation for adt7475

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On 11/6/18 8:27 PM, Chris Packham wrote:
On 7/11/18 5:24 PM, Guenter Roeck wrote:
On 11/6/18 8:00 PM, Chris Packham wrote:
With the addition of the invert-pwm property the adt7475 needs its own
binding documentation rather being captured under trivial-devices.txt.

Signed-off-by: Chris Packham <chris.packham@xxxxxxxxxxxxxxxxxxx>
---
    .../devicetree/bindings/hwmon/adt7475.txt     | 22 +++++++++++++++++++
    .../devicetree/bindings/trivial-devices.txt   |  4 ----
    2 files changed, 22 insertions(+), 4 deletions(-)
    create mode 100644 Documentation/devicetree/bindings/hwmon/adt7475.txt

diff --git a/Documentation/devicetree/bindings/hwmon/adt7475.txt b/Documentation/devicetree/bindings/hwmon/adt7475.txt
new file mode 100644
index 000000000000..79255439e157
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwmon/adt7475.txt
@@ -0,0 +1,22 @@
+*ADT7475 hwmon sensor.
+
+Required properties:
+- compatible: One of
+	"adi,adt7473"
+	"adi,adt7475"
+	"adi,adt7476"
+	"adi,adt7490"
+
+- reg: I2C address
+
+optional properties:
+
+- invert-pwm: This configures the PWM to use logic low for 100% duty cycle.
+
+Example:
+
+hwmon@2e {
+	compatible = ;
+	reg = <0x2e>;
+	invert-pwm;

If I understand correctly, the flag is set per pwm channel. A single global
property seems inappropriate.

Yes it is per-channel. But I was having a hard time imagining a hardware
design that would use both inverted and non-inverted at the same time.


People can be inventive. Sometimes too much so.

Do you have a preference for how the properties should look?

    invert-pwm[123]?

    invert-pwm = <0x7>;?

Ultimately we'll have to find a generic way of defining devicetree properties for
hardware monitoring devices, not just for pwm but for all sensor types. A sub-node
per channel seems to be the most likely answer, but I think that is a long way off
(and will require lengthy discussions about acceptable properties).

I was looking into pwm DT properties, but they define a set of flags
(PWM_POLARITY_INVERTED, PWM_POLARITY_NORMAL).

The g762 driver uses "pwm_polarity". Underscore - hmm. Other drivers use module
parameters, sysfs attributes (pwmX_invert in asc7621 driver), or platform data
(g762, max6639).

Maybe pwm-polarity = <PWM_POLARITY_NORMAL | PWM_POLARITY_INVERTED> ?
No idea if that makes sense. Or just a boolean pwm-polarity-inverted.

Thinking about it per channel vs. per chip ... other drivers also seem to
use a single property / attribute for the entire chip, so that is fine here
as well. We can always extend it if needed.

Anyway, I am fine with whatever Rob accepts.

Guenter


Guenter

+};
diff --git a/Documentation/devicetree/bindings/trivial-devices.txt b/Documentation/devicetree/bindings/trivial-devices.txt
index 69c934aec13b..4f29100d6bbf 100644
--- a/Documentation/devicetree/bindings/trivial-devices.txt
+++ b/Documentation/devicetree/bindings/trivial-devices.txt
@@ -14,10 +14,6 @@ ad,ad7414		SMBus/I2C Digital Temperature Sensor in 6-Pin SOT with SMBus Alert an
    ad,adm9240		ADM9240:  Complete System Hardware Monitor for uProcessor-Based Systems
    adi,adt7461		+/-1C TDM Extended Temp Range I.C
    adt7461			+/-1C TDM Extended Temp Range I.C
-adi,adt7473		+/-1C TDM Extended Temp Range I.C
-adi,adt7475		+/-1C TDM Extended Temp Range I.C
-adi,adt7476		+/-1C TDM Extended Temp Range I.C
-adi,adt7490		+/-1C TDM Extended Temp Range I.C
    adi,adxl345		Three-Axis Digital Accelerometer
    adi,adxl346		Three-Axis Digital Accelerometer (backward-compatibility value "adi,adxl345" must be listed too)
    ams,iaq-core		AMS iAQ-Core VOC Sensor









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