Hi Jelle,

(please Cc: linux-input ML for such questions, as I'm not the only one
 decide about that topic ... )

On Tue, May 11, 2010 at 04:10:24PM +0200, Jelle Martijn Kok wrote:

I saw you had contributed code for the rotary encoder.
We made a similar device driver, but with some differences.

Good to see more users of the driver, and merging back your changes is
definitely appreciated.

The differences:
- We increase and decrease on every "00" and "11"
- We send out input events "KEY_VOLUMEDOWN" and "KEY_VOLUMEUP".

So I made some changes to the rotary encoder files, that adds this
functionality.
Changes to the header file:
- "steps" is replaced by "initial_value" "min_value" and "max_value"
- "event_up" and "event_down" is added

"rotary_encoder.c" is modified such way that it matches these changes.

My questions:
- Is the removal of the "steps" field an issue for compatibility ?

Yes. This driver has active users, so all changes should be
backwards-compatible. We could introduce an "initial_value", but I'm
against deprecating the "steps" parameter.

- "relative mode" and the "key events" are quite similar, is this "ugly ?

No, they're not. One is an axis information, the other one is a button.
I have no problem adding the feature for button event generation,
though.

- Are you willing to make these updates to the kernel ?

Could you send your changes as patch against the current kernel's git
HEAD please? That's much easier to review.

Thanks,
Daniel

#ifndef __ROTARY_ENCODER_H__
#define __ROTARY_ENCODER_H__

struct rotary_encoder_platform_data {
	unsigned int gpio_a;
	unsigned int gpio_b;
	unsigned int inverted_a;
	unsigned int inverted_b;
	unsigned int axis;
	unsigned int initial_value;
	unsigned int min_value;
	unsigned int max_value;
	unsigned int event_up;
	unsigned int event_down;
	bool relative_axis;
	bool rollover;
};

#endif /* __ROTARY_ENCODER_H__ */

/*
 * rotary_encoder.c
 *
 * (c) 2009 Daniel Mack [off-list ref]
 *
 * state machine code inspired by code from Tim Ruetz
 *
 * A generic driver for rotary encoders connected to GPIO lines.
 * See file:Documentation/input/rotary_encoder.txt for more information
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/input.h>
#include <linux/device.h>
#include <linux/platform_device.h>
#include <linux/gpio.h>
#include <linux/rotary_encoder.h>

#define DRV_NAME "rotary-encoder"

struct rotary_encoder {
	struct input_dev *input;
	struct rotary_encoder_platform_data *pdata;

	unsigned int axis;
	unsigned int pos;

	unsigned int irq_a;
	unsigned int irq_b;

	int last_state;
	//~ bool armed;
	//~ unsigned char dir;	/* 0 - clockwise, 1 - CCW */
};

static irqreturn_t rotary_encoder_irq(int irq, void *dev_id)
{
	struct rotary_encoder *encoder = dev_id;
	struct rotary_encoder_platform_data *pdata = encoder->pdata;
	int a = !!gpio_get_value(pdata->gpio_a);
	int b = !!gpio_get_value(pdata->gpio_b);
	int state;

	a ^= pdata->inverted_a;
	b ^= pdata->inverted_b;
	state = (a << 1) | b;

	// Only process in the rest states
	if (((state == 0x0) || (state == 0x3)) && ((encoder->last_state == 0x01) || (encoder->last_state == 0x02)))  {
		int state_exor = state ^ encoder->last_state;
		int dir = 0;

		if (state_exor == 0x01) {
			dir = +1;
			if (pdata->event_up) {
				input_report_key(encoder->input, pdata->event_up, 1);
				input_report_key(encoder->input, pdata->event_up, 0);
			}
		}
		else {
			dir = -1;
			if (pdata->event_down) {
				input_report_key(encoder->input, pdata->event_down, 1);
				input_report_key(encoder->input, pdata->event_down, 0);
			}
		}

		if (dir) {
			if (pdata->relative_axis) {
				input_report_rel(encoder->input, pdata->axis, dir);
			}
			else {
				unsigned int pos = encoder->pos;

				if (dir == -1) {
					/* turning counter-clockwise */
					if (pos > pdata->min_value)
						pos--;
					else if (pdata->rollover)
						pos = pdata->max_value;
				} 
				else {
					/* turning clockwise */
					if (pos < pdata->max_value)
						pos++;
					else if (pdata->rollover)
						pos = pdata->min_value;
				}
				encoder->pos = pos;
				input_report_abs(encoder->input, pdata->axis, encoder->pos);
			}
			input_sync(encoder->input);
		}
	}

	/* always store the state - even on a 00 or 11 */
	encoder->last_state = state;

	return IRQ_HANDLED;
}

static int __devinit rotary_encoder_probe(struct platform_device *pdev)
{
	struct rotary_encoder_platform_data *pdata = pdev->dev.platform_data;
	struct rotary_encoder *encoder;
	struct input_dev *input;
	int err;

	if (!pdata) {
		dev_err(&pdev->dev, "missing platform data\n");
		return -ENOENT;
	}

	encoder = kzalloc(sizeof(struct rotary_encoder), GFP_KERNEL);
	input = input_allocate_device();
	if (!encoder || !input) {
		dev_err(&pdev->dev, "failed to allocate memory for device\n");
		err = -ENOMEM;
		goto exit_free_mem;
	}

	encoder->input = input;
	encoder->pdata = pdata;
	encoder->irq_a = gpio_to_irq(pdata->gpio_a);
	encoder->irq_b = gpio_to_irq(pdata->gpio_b);
	encoder->pos = pdata->initial_value;

	/* create and register the input driver */
	input->name = pdev->name;
	input->id.bustype = BUS_HOST;
	input->dev.parent = &pdev->dev;

	if (pdata->event_up || pdata->event_down) {
		input->evbit[0] |= BIT(EV_KEY);
		set_bit(pdata->event_up, input->keybit);
		set_bit(pdata->event_down, input->keybit);
		clear_bit(KEY_RESERVED, input->keybit);
		input_set_capability(input, EV_MSC, MSC_SCAN);
	}
	if (pdata->relative_axis) {
		input->evbit[0] |= BIT_MASK(EV_REL);
		input->relbit[0] = BIT(pdata->axis);
	}
	else {
		input->evbit[0] |= BIT_MASK(EV_ABS);
		input_set_abs_params(encoder->input, pdata->axis, 
			pdata->min_value, pdata->max_value, 
			0, 1);
	}

	err = input_register_device(input);
	if (err) {
		dev_err(&pdev->dev, "failed to register input device\n");
		goto exit_free_mem;
	}

	/* request the GPIOs */
	err = gpio_request(pdata->gpio_a, DRV_NAME);
	if (err) {
		dev_err(&pdev->dev, "unable to request GPIO %d\n",
			pdata->gpio_a);
		goto exit_unregister_input;
	}

	err = gpio_request(pdata->gpio_b, DRV_NAME);
	if (err) {
		dev_err(&pdev->dev, "unable to request GPIO %d\n",
			pdata->gpio_b);
		goto exit_free_gpio_a;
	}

	/* request the IRQs */
	err = request_irq(encoder->irq_a, &rotary_encoder_irq,
			  IORESOURCE_IRQ_HIGHEDGE | IORESOURCE_IRQ_LOWEDGE,
			  DRV_NAME, encoder);
	if (err) {
		dev_err(&pdev->dev, "unable to request IRQ %d\n",
			encoder->irq_a);
		goto exit_free_gpio_b;
	}

	err = request_irq(encoder->irq_b, &rotary_encoder_irq,
			  IORESOURCE_IRQ_HIGHEDGE | IORESOURCE_IRQ_LOWEDGE,
			  DRV_NAME, encoder);
	if (err) {
		dev_err(&pdev->dev, "unable to request IRQ %d\n",
			encoder->irq_b);
		goto exit_free_irq_a;
	}

	platform_set_drvdata(pdev, encoder);

	return 0;

exit_free_irq_a:
	free_irq(encoder->irq_a, encoder);
exit_free_gpio_b:
	gpio_free(pdata->gpio_b);
exit_free_gpio_a:
	gpio_free(pdata->gpio_a);
exit_unregister_input:
	input_unregister_device(input);
	input = NULL; /* so we don't try to free it */
exit_free_mem:
	input_free_device(input);
	kfree(encoder);
	return err;
}

static int __devexit rotary_encoder_remove(struct platform_device *pdev)
{
	struct rotary_encoder *encoder = platform_get_drvdata(pdev);
	struct rotary_encoder_platform_data *pdata = pdev->dev.platform_data;

	free_irq(encoder->irq_a, encoder);
	free_irq(encoder->irq_b, encoder);
	gpio_free(pdata->gpio_a);
	gpio_free(pdata->gpio_b);
	input_unregister_device(encoder->input);
	platform_set_drvdata(pdev, NULL);
	kfree(encoder);

	return 0;
}

static struct platform_driver rotary_encoder_driver = {
	.probe		= rotary_encoder_probe,
	.remove		= __devexit_p(rotary_encoder_remove),
	.driver		= {
		.name	= DRV_NAME,
		.owner	= THIS_MODULE,
	}
};

static int __init rotary_encoder_init(void)
{
	return platform_driver_register(&rotary_encoder_driver);
}

static void __exit rotary_encoder_exit(void)
{
	platform_driver_unregister(&rotary_encoder_driver);
}

module_init(rotary_encoder_init);
module_exit(rotary_encoder_exit);

MODULE_ALIAS("platform:" DRV_NAME);
MODULE_DESCRIPTION("GPIO rotary encoder driver");
MODULE_AUTHOR("Daniel Mack [off-list ref]");
MODULE_LICENSE("GPL v2");