Re: [RFC PATCH 1/2] Input: rotary-encoder- Add support for absolute encoder

[Krzysztof Kozlowski]

On 05/19/2016 11:04 AM, Vignesh R wrote:
> There are rotary-encoders where GPIO lines reflect the actual position
> of the rotary encoder dial. For example, if dial points to 9, then four
> GPIO lines connected to the rotary encoder will read HLLH(1001b = 9).
> Add support for such rotary-encoder.
> The driver relies on rotary-encoder,absolute-encoder DT property to
> detect such encoders.
> Since, GPIO IRQs are not necessary to work with
> such encoders, optional polling mode support is added using
> input_poll_dev skeleton. This is can be used by enabling
> CONFIG_INPUT_GPIO_ROTARY_ENCODER_POLL_MODE_SUPPORT.
> 
> Signed-off-by: Vignesh R <vigneshr@xxxxxx>
> ---
>  .../devicetree/bindings/input/rotary-encoder.txt   |   4 +
>  Documentation/input/rotary-encoder.txt             |   9 ++
>  drivers/input/misc/Kconfig                         |  11 ++
>  drivers/input/misc/rotary_encoder.c                | 165 ++++++++++++++++-----
>  4 files changed, 155 insertions(+), 34 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/input/rotary-encoder.txt b/Documentation/devicetree/bindings/input/rotary-encoder.txt
> index 6c9f0c8a846c..9c928dbd1500 100644
> --- a/Documentation/devicetree/bindings/input/rotary-encoder.txt
> +++ b/Documentation/devicetree/bindings/input/rotary-encoder.txt
> @@ -12,6 +12,10 @@ Optional properties:
>  - rotary-encoder,relative-axis: register a relative axis rather than an
>    absolute one. Relative axis will only generate +1/-1 events on the input
>    device, hence no steps need to be passed.
> +- rotary-encoder,absolute-encoder: support encoders where GPIO lines
> +  reflect the actual position of the rotary encoder dial. For example,
> +  if dial points to 9, then four GPIO lines read HLLH(1001b = 9).
> +  In this case, rotary-encoder,steps-per-period needed not be defined.
>  - rotary-encoder,rollover: Automatic rollove when the rotary value becomes
>    greater than the specified steps or smaller than 0. For absolute axis only.
>  - rotary-encoder,steps-per-period: Number of steps (stable states) per period.
> diff --git a/Documentation/input/rotary-encoder.txt b/Documentation/input/rotary-encoder.txt
> index 46a74f0c551a..dc76092f5618 100644
> --- a/Documentation/input/rotary-encoder.txt
> +++ b/Documentation/input/rotary-encoder.txt
> @@ -36,6 +36,15 @@ The phase diagram of these two outputs look like this:
>                  |<>|
>  	          one step (quarter-period mode)
>  
> +
> +In some encoders, the value pointed by rotary encoders switch is directly
> +reflected by status of the GPIOs connecting rotary encoder to CPU. For
> +example, if rotary encoder dial points to 9, then the four GPIOs
> +conncting rotary encoder will read HLLH(1001b = 9). Such encoders are
> +supported by defining devictree binding "rotary-encoder,absolute-encoder".
> +These encoders are also supported without need for event(IRQ) generation
> +using Input subsytem's polling mode support.
> +
>  For more information, please see
>  	https://en.wikipedia.org/wiki/Rotary_encoder
>  
> diff --git a/drivers/input/misc/Kconfig b/drivers/input/misc/Kconfig
> index 1f2337abcf2f..81805f9a534c 100644
> --- a/drivers/input/misc/Kconfig
> +++ b/drivers/input/misc/Kconfig
> @@ -566,6 +566,17 @@ config INPUT_GPIO_ROTARY_ENCODER
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called rotary_encoder.
>  
> +config INPUT_GPIO_ROTARY_ENCODER_POLL_MODE_SUPPORT
> +	bool "Polling mode support for rotary encoder"
> +	depends on INPUT_GPIO_ROTARY_ENCODER
> +	select INPUT_POLLDEV
> +	help
> +	  Say Y here to enable polling mode support for rotary encoders
> +	  connected to GPIO lines that do have interrupt capability and
> +	  report rotary encoder position as absolute value over GPIO
> +	  lines. Check file: Documentation/input/rotary-encoder.txt for
> +	  more information.
> +
>  config INPUT_RB532_BUTTON
>  	tristate "Mikrotik Routerboard 532 button interface"
>  	depends on MIKROTIK_RB532
> diff --git a/drivers/input/misc/rotary_encoder.c b/drivers/input/misc/rotary_encoder.c
> index c7fc8d4fb080..8f60289fb6cd 100644
> --- a/drivers/input/misc/rotary_encoder.c
> +++ b/drivers/input/misc/rotary_encoder.c
> @@ -25,24 +25,29 @@
>  #include <linux/of.h>
>  #include <linux/pm.h>
>  #include <linux/property.h>
> +#include <linux/input-polldev.h>
>  
>  #define DRV_NAME "rotary-encoder"
>  
>  struct rotary_encoder {
>  	struct input_dev *input;
> -
> +#ifdef CONFIG_INPUT_GPIO_ROTARY_ENCODER_POLL_MODE_SUPPORT

Ifdefs look dirty.

> +	struct input_polled_dev *poll_dev;
> +#endif
>  	struct mutex access_mutex;
>  
>  	u32 steps;
>  	u32 axis;
>  	bool relative_axis;
>  	bool rollover;
> +	bool absolute_encoder;
>  
>  	unsigned int pos;
>  
>  	struct gpio_descs *gpios;
> +	struct device *dev;
>  
> -	unsigned int *irq;
> +	int *irq;
>  
>  	bool armed;
>  	signed char dir;	/* 1 - clockwise, -1 - CCW */
> @@ -67,6 +72,21 @@ static unsigned int rotary_encoder_get_state(struct rotary_encoder *encoder)
>  	return ret & 3;
>  }
>  
> +static unsigned int rotary_encoder_get_gpios_state(struct rotary_encoder
> +						   *encoder)
> +{
> +	int i;
> +	unsigned int ret = 0;
> +
> +	for (i = 0; i < encoder->gpios->ndescs; ++i) {
> +		int val = gpiod_get_value_cansleep(encoder->gpios->desc[i]);
> +
> +		ret = ret << 1 | val;
> +	}
> +
> +	return ret;
> +}
> +
>  static void rotary_encoder_report_event(struct rotary_encoder *encoder)
>  {
>  	if (encoder->relative_axis) {
> @@ -178,6 +198,72 @@ out:
>  	return IRQ_HANDLED;
>  }
>  
> +static void rotary_encoder_setup_input_params(struct rotary_encoder  *encoder)
> +{
> +	struct input_dev *input = encoder->input;
> +	struct platform_device *pdev = to_platform_device(encoder->dev);
> +
> +	input->name = pdev->name;
> +	input->id.bustype = BUS_HOST;
> +	input->dev.parent = encoder->dev;
> +
> +	if (encoder->relative_axis)
> +		input_set_capability(input, EV_REL, encoder->axis);
> +	else
> +		input_set_abs_params(input,
> +				     encoder->axis, 0, encoder->steps, 0, 1);
> +}
> +
> +static irqreturn_t rotary_absolute_encoder_irq(int irq, void *dev_id)
> +{
> +	struct rotary_encoder *encoder = dev_id;
> +	unsigned int state;
> +
> +	mutex_lock(&encoder->access_mutex);
> +
> +	state = rotary_encoder_get_gpios_state(encoder);
> +	if (state != encoder->last_stable) {
> +		input_report_abs(encoder->input, encoder->axis, state);
> +		input_sync(encoder->input);
> +		encoder->last_stable = state;
> +	}
> +
> +	mutex_lock(&encoder->access_mutex);

1. Double mutex_lock()? Oh, that is weird. Please document it at least
in form of lockdep annotations.

2. Maybe that should be unlock? Did you test this code?

> +
> +	return IRQ_HANDLED;
> +}
> +
> +#ifdef CONFIG_INPUT_GPIO_ROTARY_ENCODER_POLL_MODE_SUPPORT

Same here and later in the code, ifdefs look dirty.

Best regards,
Krzysztof