[PATCH v2] Input: rotary_encoder - support binary encoding of states

[PATCH v2] Input: rotary_encoder - support binary encoding of states

[Uwe Kleine-König]

It's not advisable to use this encoding, but to support existing devices
add support for this to the driver.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---

Notes:
    Changes since (implicit) v1, sent with
    Message-Id: 1458680914-4533-1-git-send-email-u.kleine-koenig@pengutronix.de
    
     - switch format of dt properties to use strings

 .../devicetree/bindings/input/rotary-encoder.txt   |  4 ++++
 drivers/input/misc/rotary_encoder.c                | 22 +++++++++++++++++++---
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/input/rotary-encoder.txt b/Documentation/devicetree/bindings/input/rotary-encoder.txt
index 6c9f0c8a846c..e85ce3dea480 100644
--- a/Documentation/devicetree/bindings/input/rotary-encoder.txt
+++ b/Documentation/devicetree/bindings/input/rotary-encoder.txt
@@ -20,6 +20,8 @@ Optional properties:
   2: Half-period mode
   4: Quarter-period mode
 - wakeup-source: Boolean, rotary encoder can wake up the system.
+- rotary-encoder,encoding: String, the method used to encode steps.
+  Supported are "gray" (the default and more common) and "binary".
 
 Deprecated properties:
 - rotary-encoder,half-period: Makes the driver work on half-period mode.
@@ -34,6 +36,7 @@ Example:
 			compatible = "rotary-encoder";
 			gpios = <&gpio 19 1>, <&gpio 20 0>; /* GPIO19 is inverted */
 			linux,axis = <0>; /* REL_X */
+			rotary-encoder,encoding = "gray";
 			rotary-encoder,relative-axis;
 		};
 
@@ -42,5 +45,6 @@ Example:
 			gpios = <&gpio 21 0>, <&gpio 22 0>;
 			linux,axis = <1>; /* ABS_Y */
 			rotary-encoder,steps = <24>;
+			rotary-encoder,encoding = "binary";
 			rotary-encoder,rollover;
 		};
diff --git a/drivers/input/misc/rotary_encoder.c b/drivers/input/misc/rotary_encoder.c
index 96c486de49e0..d226d69a174a 100644
--- a/drivers/input/misc/rotary_encoder.c
+++ b/drivers/input/misc/rotary_encoder.c
@@ -28,6 +28,11 @@
 
 #define DRV_NAME "rotary-encoder"
 
+enum rotary_encoder_encoding {
+	ROTENC_GRAY,
+	ROTENC_BINARY,
+};
+
 struct rotary_encoder {
 	struct input_dev *input;
 
@@ -37,6 +42,7 @@ struct rotary_encoder {
 	u32 axis;
 	bool relative_axis;
 	bool rollover;
+	enum rotary_encoder_encoding encoding;
 
 	unsigned int pos;
 
@@ -57,9 +63,11 @@ static unsigned rotary_encoder_get_state(struct rotary_encoder *encoder)
 
 	for (i = 0; i < encoder->gpios->ndescs; ++i) {
 		int val = gpiod_get_value_cansleep(encoder->gpios->desc[i]);
-		/* convert from gray encoding to normal */
-		if (ret & 1)
-			val = !val;
+
+		if (encoder->encoding == ROTENC_GRAY)
+			/* convert from gray encoding to binary */
+			if (ret & 1)
+				val = !val;
 
 		ret = ret << 1 | val;
 	}
@@ -183,6 +191,7 @@ static int rotary_encoder_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	struct rotary_encoder *encoder;
 	struct input_dev *input;
+	const char *encoding;
 	irq_handler_t handler;
 	u32 steps_per_period;
 	unsigned int i;
@@ -213,6 +222,13 @@ static int rotary_encoder_probe(struct platform_device *pdev)
 	encoder->rollover =
 		device_property_read_bool(dev, "rotary-encoder,rollover");
 
+	err = device_property_read_string(dev, "rotary-encoder,encoding",
+					  &encoding);
+	if (!err && encoding[0] == 'b')
+		encoder->encoding = ROTENC_BINARY;
+	else
+		encoder->encoding = ROTENC_GRAY;
+
 	device_property_read_u32(dev, "linux,axis", &encoder->axis);
 	encoder->relative_axis =
 		device_property_read_bool(dev, "rotary-encoder,relative-axis");
-- 
2.7.0

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Re: [PATCH v2] Input: rotary_encoder - support binary encoding of states

[Rob Herring]

On Thu, Mar 24, 2016 at 08:57:12AM +0100, Uwe Kleine-König wrote:
> It's not advisable to use this encoding, but to support existing devices
> add support for this to the driver.
> 
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> ---
> 
> Notes:
>     Changes since (implicit) v1, sent with
>     Message-Id: 1458680914-4533-1-git-send-email-u.kleine-koenig@pengutronix.de
>     
>      - switch format of dt properties to use strings
> 
>  .../devicetree/bindings/input/rotary-encoder.txt   |  4 ++++
>  drivers/input/misc/rotary_encoder.c                | 22 +++++++++++++++++++---
>  2 files changed, 23 insertions(+), 3 deletions(-)

Acked-by: Rob Herring <robh@kernel.org>
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Re: [PATCH v2] Input: rotary_encoder - support binary encoding of states

[Dmitry Torokhov]

On Thu, Mar 24, 2016 at 08:57:12AM +0100, Uwe Kleine-König wrote:
> It's not advisable to use this encoding, but to support existing devices
> add support for this to the driver.
> 
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> ---
> 
> Notes:
>     Changes since (implicit) v1, sent with
>     Message-Id: 1458680914-4533-1-git-send-email-u.kleine-koenig@pengutronix.de
>     
>      - switch format of dt properties to use strings
> 
>  .../devicetree/bindings/input/rotary-encoder.txt   |  4 ++++
>  drivers/input/misc/rotary_encoder.c                | 22 +++++++++++++++++++---
>  2 files changed, 23 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/input/rotary-encoder.txt b/Documentation/devicetree/bindings/input/rotary-encoder.txt
> index 6c9f0c8a846c..e85ce3dea480 100644
> --- a/Documentation/devicetree/bindings/input/rotary-encoder.txt
> +++ b/Documentation/devicetree/bindings/input/rotary-encoder.txt
> @@ -20,6 +20,8 @@ Optional properties:
>    2: Half-period mode
>    4: Quarter-period mode
>  - wakeup-source: Boolean, rotary encoder can wake up the system.
> +- rotary-encoder,encoding: String, the method used to encode steps.
> +  Supported are "gray" (the default and more common) and "binary".
>  
>  Deprecated properties:
>  - rotary-encoder,half-period: Makes the driver work on half-period mode.
> @@ -34,6 +36,7 @@ Example:
>  			compatible = "rotary-encoder";
>  			gpios = <&gpio 19 1>, <&gpio 20 0>; /* GPIO19 is inverted */
>  			linux,axis = <0>; /* REL_X */
> +			rotary-encoder,encoding = "gray";
>  			rotary-encoder,relative-axis;
>  		};
>  
> @@ -42,5 +45,6 @@ Example:
>  			gpios = <&gpio 21 0>, <&gpio 22 0>;
>  			linux,axis = <1>; /* ABS_Y */
>  			rotary-encoder,steps = <24>;
> +			rotary-encoder,encoding = "binary";
>  			rotary-encoder,rollover;
>  		};
> diff --git a/drivers/input/misc/rotary_encoder.c b/drivers/input/misc/rotary_encoder.c
> index 96c486de49e0..d226d69a174a 100644
> --- a/drivers/input/misc/rotary_encoder.c
> +++ b/drivers/input/misc/rotary_encoder.c
> @@ -28,6 +28,11 @@
>  
>  #define DRV_NAME "rotary-encoder"
>  
> +enum rotary_encoder_encoding {
> +	ROTENC_GRAY,
> +	ROTENC_BINARY,
> +};
> +
>  struct rotary_encoder {
>  	struct input_dev *input;
>  
> @@ -37,6 +42,7 @@ struct rotary_encoder {
>  	u32 axis;
>  	bool relative_axis;
>  	bool rollover;
> +	enum rotary_encoder_encoding encoding;
>  
>  	unsigned int pos;
>  
> @@ -57,9 +63,11 @@ static unsigned rotary_encoder_get_state(struct rotary_encoder *encoder)
>  
>  	for (i = 0; i < encoder->gpios->ndescs; ++i) {
>  		int val = gpiod_get_value_cansleep(encoder->gpios->desc[i]);
> -		/* convert from gray encoding to normal */
> -		if (ret & 1)
> -			val = !val;
> +
> +		if (encoder->encoding == ROTENC_GRAY)
> +			/* convert from gray encoding to binary */
> +			if (ret & 1)
> +				val = !val;
>  
>  		ret = ret << 1 | val;
>  	}
> @@ -183,6 +191,7 @@ static int rotary_encoder_probe(struct platform_device *pdev)
>  	struct device *dev = &pdev->dev;
>  	struct rotary_encoder *encoder;
>  	struct input_dev *input;
> +	const char *encoding;
>  	irq_handler_t handler;
>  	u32 steps_per_period;
>  	unsigned int i;
> @@ -213,6 +222,13 @@ static int rotary_encoder_probe(struct platform_device *pdev)
>  	encoder->rollover =
>  		device_property_read_bool(dev, "rotary-encoder,rollover");
>  
> +	err = device_property_read_string(dev, "rotary-encoder,encoding",
> +					  &encoding);
> +	if (!err && encoding[0] == 'b')

Why do we only match on first letter? I'd prefer we did better parsing
(i.e. only accepted valid encodings or no encoding property.

> +		encoder->encoding = ROTENC_BINARY;
> +	else
> +		encoder->encoding = ROTENC_GRAY;
> +
>  	device_property_read_u32(dev, "linux,axis", &encoder->axis);
>  	encoder->relative_axis =
>  		device_property_read_bool(dev, "rotary-encoder,relative-axis");
> -- 
> 2.7.0
> 

Thanks.

-- 
Dmitry
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Re: [PATCH v2] Input: rotary_encoder - support binary encoding of states

[Uwe Kleine-König]

Hello Dmitry,

On Thu, Apr 07, 2016 at 11:15:13AM -0700, Dmitry Torokhov wrote:
> On Thu, Mar 24, 2016 at 08:57:12AM +0100, Uwe Kleine-König wrote:
> > diff --git a/Documentation/devicetree/bindings/input/rotary-encoder.txt b/Documentation/devicetree/bindings/input/rotary-encoder.txt
> > index 6c9f0c8a846c..e85ce3dea480 100644
> > --- a/Documentation/devicetree/bindings/input/rotary-encoder.txt
> > +++ b/Documentation/devicetree/bindings/input/rotary-encoder.txt
> > @@ -20,6 +20,8 @@ Optional properties:
> >    2: Half-period mode
> >    4: Quarter-period mode
> >  - wakeup-source: Boolean, rotary encoder can wake up the system.
> > +- rotary-encoder,encoding: String, the method used to encode steps.
> > +  Supported are "gray" (the default and more common) and "binary".
> >  
> >  Deprecated properties:
> >  - rotary-encoder,half-period: Makes the driver work on half-period mode.
> > [...]
> > +	err = device_property_read_string(dev, "rotary-encoder,encoding",
> > +					  &encoding);
> > +	if (!err && encoding[0] == 'b')
> 
> Why do we only match on first letter? I'd prefer we did better parsing
> (i.e. only accepted valid encodings or no encoding property.

IMHO it's not a problem that

	rotary-encoder,encoding = "blablubfasel";

isn't rejected by interpretet as "binary" instead. That's a bit like
compilers that are free to do whatever they want if the source code
contains something non-standard or undefined.

But I admit this might become a problem when the set of allowed
encodings is expanded in the future. So I will resend a more stricter
version.

Best regards
Uwe

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Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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