This patch adds a generic driver for rotary encoders connected to GPIO pins of a system. It relies on gpiolib and generic hardware irqs. The documentation that also comes with this patch explains the concept and how to use the driver. Signed-off-by: Daniel Mack <daniel@xxxxxxxx> --- new version with a stupid bug fixed. Documentation/input/rotary-encoder.txt | 110 +++++++++++++++ drivers/input/misc/Kconfig | 11 ++ drivers/input/misc/Makefile | 2 + drivers/input/misc/rotary_encoder.c | 233 ++++++++++++++++++++++++++++++++ 4 files changed, 356 insertions(+), 0 deletions(-) create mode 100644 Documentation/input/rotary-encoder.txt create mode 100644 drivers/input/misc/rotary_encoder.c diff --git a/Documentation/input/rotary-encoder.txt b/Documentation/input/rotary-encoder.txt new file mode 100644 index 0000000..5ec940c --- /dev/null +++ b/Documentation/input/rotary-encoder.txt @@ -0,0 +1,110 @@ +rotary-encoder - a generic driver for GPIO connected devices +Daniel Mack <daniel@xxxxxxxx>, Feb 2009 + +0. Function +----------- + +Rotary encoders are devices which are connected to the CPU or other +peripherals with two wires. The outputs are phase-shifted by 90 degrees +and by triggering on falling and rising edges, the turn direction can +be determined. + +The phase diagram of these two outputs look like this: + + _____ _____ _____ + | | | | | | + Channel A ____| |_____| |_____| |____ + + : : : : : : : : : : : : + __ _____ _____ _____ + | | | | | | | + Channel B |_____| |_____| |_____| |__ + + : : : : : : : : : : : : + Event a b c d a b c d a b c d + + |<-------->| + one step + + +For more information, please see + http://en.wikipedia.org/wiki/Rotary_encoder + + +1. Events / state machine +------------------------- + +a) Rising edge on channel A, channel B in low state + This state is used to recognize a clockwise turn + +b) Rising edge on channel B, channel A in high state + When entering this state, the encoder is put into 'armed' state, + meaning that there it has seen half the way of a one-step transition. + +c) Falling edge on channel A, channel B in high state + This state is used to recognize a counter-clockwise turn + +d) Falling edge on channel B, channel A in low state + Parking position. If the encoder enters this state, a full transition + should have happend, unless it flipped back on half the way. The + 'armed' state tells us about that. + +2. Platform requirements +------------------------ + +As there is no hardware dependent call in this driver, the platform it is +used with must support gpiolib. Another requirement is that IRQs must be +able to fire on both edges. + + +3. Board integration +-------------------- + +To use this driver in your system, register a platform_device with the +name 'rotary-encoder' and associate the IRQs and some specific platform +data with it. + +struct rotary_encoder_platform_data is declared in +include/linux/rotary-encoder.h and needs to be filled with the number of +steps the encoder has and can carry information about externally inverted +signals (because of used invertig buffer or other reasons). + +Because GPIO to IRQ mapping is platform specific, this information must +be given in seperately to the driver. See the example below. + +---------<snip>--------- + +/* board support file example */ + +#define GPIO_ROTARY_A 1 +#define GPIO_ROTARY_B 2 + +static struct resource rotary_encoder_resources[] = { + [0] = { + .flags = IORESOURCE_IRQ, + .start = IRQ_GPIO(GPIO_ROTARY_A) + }, + [1] = { + .flags = IORESOURCE_IRQ, + .start = IRQ_GPIO(GPIO_ROTARY_B) + } +}; + +static struct rotary_encoder_platform_data my_rotary_encoder_info = { + .steps = 24, + .gpio_a = GPIO_ROTARY_A, + .gpio_b = GPIO_ROTARY_B, + .inverted_a = 0, + .inverted_b = 0, +}; + +static struct platform_device rotary_encoder_device = { + .name = "rotary-encoder", + .id = 0, + .num_resources = ARRAY_SIZE(rotary_encoder_resources), + .resource = rotary_encoder_resources, + .dev = { + .platform_data = &my_rotary_encoder_info, + } +}; + diff --git a/drivers/input/misc/Kconfig b/drivers/input/misc/Kconfig index 67e5553..b2678de 100644 --- a/drivers/input/misc/Kconfig +++ b/drivers/input/misc/Kconfig @@ -227,4 +227,15 @@ config INPUT_PCF50633_PMU Say Y to include support for delivering PMU events via input layer on NXP PCF50633. +config INPUT_GPIO_ROTARY_ENCODER + tristate "Rotary encoders connected to GPIO pins" + depends on GPIOLIB && GENERIC_GPIO && GENERIC_HARDIRQS + help + Say Y here to add support for rotary encoders connected to GPIO lines. + Check file:Documentation/incput/rotary_encoder.txt for more + information. + + To compile this driver as a module, choose M here: the + module will be called rotary_encoder. + endif diff --git a/drivers/input/misc/Makefile b/drivers/input/misc/Makefile index bb62e6e..e86cee6 100644 --- a/drivers/input/misc/Makefile +++ b/drivers/input/misc/Makefile @@ -22,3 +22,5 @@ obj-$(CONFIG_INPUT_UINPUT) += uinput.o obj-$(CONFIG_INPUT_APANEL) += apanel.o obj-$(CONFIG_INPUT_SGI_BTNS) += sgi_btns.o obj-$(CONFIG_INPUT_PCF50633_PMU) += pcf50633-input.o +obj-$(CONFIG_INPUT_GPIO_ROTARY_ENCODER) += rotary_encoder.o + diff --git a/drivers/input/misc/rotary_encoder.c b/drivers/input/misc/rotary_encoder.c new file mode 100644 index 0000000..4f970dc --- /dev/null +++ b/drivers/input/misc/rotary_encoder.c @@ -0,0 +1,233 @@ +/* + * rotary_encoder.c + * + * (c) 2009 Daniel Mack <daniel@xxxxxxxx> + * + * 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 { + unsigned int irq_a; + unsigned int irq_b; + unsigned int pos; + unsigned int armed; + unsigned int dir; + struct input_dev *input; + struct rotary_encoder_platform_data *pdata; +}; + +static void rotary_encoder_left(struct rotary_encoder *encoder) +{ + encoder->pos += encoder->pdata->steps; + encoder->pos--; + encoder->pos %= encoder->pdata->steps; + input_report_abs(encoder->input, ABS_X, encoder->pos); + input_sync(encoder->input); +} + +static void rotary_encoder_right(struct rotary_encoder *encoder) +{ + encoder->pos++; + encoder->pos %= encoder->pdata->steps; + input_report_abs(encoder->input, ABS_X, encoder->pos); + input_sync(encoder->input); +} + +static irqreturn_t rotary_encoder_irq(int irq, void *dev_id) +{ + struct rotary_encoder *encoder = dev_id; + int a = !!gpio_get_value(encoder->pdata->gpio_a); + int b = !!gpio_get_value(encoder->pdata->gpio_b); + int state; + + a ^= encoder->pdata->inverted_a; + b ^= encoder->pdata->inverted_b; + state = (a << 1) | b; + + switch (state) { + case 0x0: + if (!encoder->armed) + break; + + if (encoder->dir) + rotary_encoder_left(encoder); + else + rotary_encoder_right(encoder); + + encoder->armed = 0; + break; + case 0x1: + case 0x2: + if (!encoder->armed) + break; + + encoder->dir = state - 1; + break; + case 0x3: + encoder->armed = 1; + break; + } + + return IRQ_HANDLED; +} + +static int __devinit rotary_encoder_probe(struct platform_device *pdev) +{ + struct rotary_encoder *encoder; + struct resource *irq_a_res; + struct resource *irq_b_res; + unsigned long irq_flags; + int err; + + encoder = kzalloc(sizeof(struct rotary_encoder), GFP_KERNEL); + if (!encoder) { + dev_err(&pdev->dev, "failed to allocate driver data\n"); + err = -ENOMEM; + goto exit; + } + + irq_flags = IORESOURCE_IRQ_HIGHEDGE | IORESOURCE_IRQ_LOWEDGE; + irq_a_res = platform_get_resource(pdev, IORESOURCE_IRQ, 0); + irq_b_res = platform_get_resource(pdev, IORESOURCE_IRQ, 1); + encoder->pdata = pdev->dev.platform_data; + + if (!irq_a_res || !irq_b_res || !encoder->pdata) { + dev_err(&pdev->dev, "insufficient resources\n"); + err = -ENOENT; + goto exit_free_mem; + } + + encoder->irq_a = irq_a_res->start; + encoder->irq_b = irq_b_res->start; + + /* create and register the input driver */ + encoder->input = input_allocate_device(); + if (!encoder->input) { + dev_err(&pdev->dev, "failed to allocate input device\n"); + err = -ENOMEM; + goto exit_free_mem; + } + + encoder->input->name = pdev->name; + encoder->input->id.bustype = BUS_HOST; + encoder->input->dev.parent = &pdev->dev; + encoder->input->evbit[0] = BIT_MASK(EV_ABS); + encoder->input->absbit[0] = BIT_MASK(ABS_X); + input_set_abs_params(encoder->input, ABS_X, 0, + encoder->pdata->steps, 0, 1); + platform_set_drvdata(pdev, encoder); + + err = input_register_device(encoder->input); + if (err) { + dev_err(&pdev->dev, "failed to register input device\n"); + goto exit_free_input; + } + + /* request the GPIOs */ + err = gpio_request(encoder->pdata->gpio_a, DRV_NAME); + if (err) { + dev_err(&pdev->dev, "unable to request GPIO %d\n", + encoder->pdata->gpio_a); + goto exit_free_input; + } + + err = gpio_request(encoder->pdata->gpio_b, DRV_NAME); + if (err) { + dev_err(&pdev->dev, "unable to request GPIO %d\n", + encoder->pdata->gpio_b); + goto exit_free_gpio_a; + } + + /* request the IRQs */ + err = request_irq(encoder->irq_a, &rotary_encoder_irq, + irq_flags, DRV_NAME, encoder); + if (err) { + dev_err(&pdev->dev, "unable to request IRQ %d\n", + encoder->irq_a); + goto exit_free_gpio; + } + + err = request_irq(encoder->irq_b, &rotary_encoder_irq, + irq_flags, DRV_NAME, encoder); + if (err) { + dev_err(&pdev->dev, "unable to request IRQ %d\n", + encoder->irq_b); + goto exit_free_irq_a; + } + + return 0; + +exit_free_irq_a: + free_irq(encoder->irq_a, encoder); +exit_free_gpio: + gpio_free(encoder->pdata->gpio_b); +exit_free_gpio_a: + gpio_free(encoder->pdata->gpio_a); +exit_free_input: + input_free_device(encoder->input); +exit_free_mem: + kfree(encoder); +exit: + return err; +} + + +static int __devexit rotary_encoder_remove(struct platform_device *pdev) +{ + struct rotary_encoder *encoder = platform_get_drvdata(pdev); + gpio_free(encoder->pdata->gpio_a); + gpio_free(encoder->pdata->gpio_b); + free_irq(encoder->irq_a, encoder); + free_irq(encoder->irq_b, encoder); + input_free_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 <daniel@xxxxxxxx>"); +MODULE_LICENSE("GPL v2"); + -- 1.6.1.3 -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
