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The driver requests edge-triggered interrupts on the A and B (and optional Index) GPIOs and decodes the quadrature signal in software using a classic state-table approach. Supported counting modes: - Quadrature X1 (count on A rising edge only) - Quadrature X2 (count on both A edges) - Quadrature X4 (count on every A and B edge) - Pulse-direction (A = pulse, B = direction) An optional index signal resets the count to zero on its rising edge when enabled through sysfs. A configurable ceiling clamps the count to [0, ceiling]. Signed-off-by: Wadim Mueller --- drivers/counter/Kconfig | 15 + drivers/counter/Makefile | 1 + drivers/counter/gpio-quadrature-encoder.c | 710 ++++++++++++++++++++++ 3 files changed, 726 insertions(+) create mode 100644 drivers/counter/gpio-quadrature-encoder.c diff --git a/drivers/counter/Kconfig b/drivers/counter/Kconfig index d30d22dfe..72c5c8159 100644 --- a/drivers/counter/Kconfig +++ b/drivers/counter/Kconfig @@ -68,6 +68,21 @@ config INTEL_QEP To compile this driver as a module, choose M here: the module will be called intel-qep. +config GPIO_QUADRATURE_ENCODER + tristate "GPIO-based quadrature encoder counter driver" + depends on GPIOLIB + help + Select this option to enable the GPIO-based quadrature encoder + counter driver. It reads A/B quadrature signals and an optional + index pulse via edge-triggered GPIO interrupts, supporting X1, X2, + X4 quadrature decoding and pulse-direction mode. + + This is useful on SoCs that lack a dedicated hardware quadrature + decoder or where the encoder is wired to generic GPIO pins. + + To compile this driver as a module, choose M here: the + module will be called gpio-quadrature-encoder. + config INTERRUPT_CNT tristate "Interrupt counter driver" depends on GPIOLIB diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile index fa3c1d08f..2bef64d10 100644 --- a/drivers/counter/Makefile +++ b/drivers/counter/Makefile @@ -14,6 +14,7 @@ obj-$(CONFIG_STM32_TIMER_CNT) += stm32-timer-cnt.o obj-$(CONFIG_STM32_LPTIMER_CNT) += stm32-lptimer-cnt.o obj-$(CONFIG_TI_EQEP) += ti-eqep.o obj-$(CONFIG_FTM_QUADDEC) += ftm-quaddec.o +obj-$(CONFIG_GPIO_QUADRATURE_ENCODER) += gpio-quadrature-encoder.o obj-$(CONFIG_MICROCHIP_TCB_CAPTURE) += microchip-tcb-capture.o obj-$(CONFIG_INTEL_QEP) += intel-qep.o obj-$(CONFIG_TI_ECAP_CAPTURE) += ti-ecap-capture.o diff --git a/drivers/counter/gpio-quadrature-encoder.c b/drivers/counter/gpio-quadrature-encoder.c new file mode 100644 index 000000000..0822f0a8a --- /dev/null +++ b/drivers/counter/gpio-quadrature-encoder.c @@ -0,0 +1,710 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * GPIO-based Quadrature Encoder Counter Driver + * + * Reads quadrature encoder signals (A, B, and optional Index) via GPIOs. + * Supports X1, X2, X4 quadrature decoding and pulse-direction mode. + * + * Copyright (C) 2026 CMBlu Energy AG + * Author: Wadim Mueller + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +enum gpio_qenc_function { + GPIO_QENC_FUNC_QUAD_X1 = 0, + GPIO_QENC_FUNC_QUAD_X2, + GPIO_QENC_FUNC_QUAD_X4, + GPIO_QENC_FUNC_PULSE_DIR, +}; + +enum gpio_qenc_signal_id { + GPIO_QENC_SIGNAL_A = 0, + GPIO_QENC_SIGNAL_B, + GPIO_QENC_SIGNAL_INDEX, +}; + +struct gpio_qenc_priv { + struct gpio_desc *gpio_a; + struct gpio_desc *gpio_b; + struct gpio_desc *gpio_index; + + int irq_a; + int irq_b; + int irq_index; + + spinlock_t lock; + + s64 count; + u64 ceiling; + bool enabled; + enum counter_count_direction direction; + enum gpio_qenc_function function; + + int prev_a; + int prev_b; + + bool index_enabled; + + struct counter_signal signals[3]; + struct counter_synapse synapses[3]; + struct counter_count cnts; +}; + +/* + * Quadrature state table for X4 decoding. + * Rows = previous state (A<<1 | B), Columns = new state (A<<1 | B). + * Values: 0 = no change, +1 = forward, -1 = backward, 2 = error (skip). + */ +static const int quad_table[4][4] = { + /* 00 01 10 11 <- new */ + /* 00 */ { 0, -1, 1, 2 }, + /* 01 */ { 1, 0, 2, -1 }, + /* 10 */ { -1, 2, 0, 1 }, + /* 11 */ { 2, 1, -1, 0 }, +}; + +static void gpio_qenc_update_count(struct gpio_qenc_priv *priv, int delta) +{ + s64 new_count; + + if (!delta) + return; + + new_count = priv->count + delta; + + if (priv->ceiling) { + if (new_count < 0) + new_count = 0; + else if (new_count > (s64)priv->ceiling) + new_count = priv->ceiling; + } + + priv->count = new_count; + priv->direction = (delta > 0) ? COUNTER_COUNT_DIRECTION_FORWARD + : COUNTER_COUNT_DIRECTION_BACKWARD; +} + +static irqreturn_t gpio_qenc_a_isr(int irq, void *dev_id) +{ + struct counter_device *counter = dev_id; + struct gpio_qenc_priv *priv = counter_priv(counter); + unsigned long flags; + int a, b, prev_state, new_state, delta; + + spin_lock_irqsave(&priv->lock, flags); + + if (!priv->enabled) + goto out; + + a = gpiod_get_value(priv->gpio_a); + b = gpiod_get_value(priv->gpio_b); + + prev_state = (priv->prev_a << 1) | priv->prev_b; + new_state = (a << 1) | b; + + switch (priv->function) { + case GPIO_QENC_FUNC_QUAD_X4: + delta = quad_table[prev_state][new_state]; + if (delta == 2) + delta = 0; + gpio_qenc_update_count(priv, delta); + break; + + case GPIO_QENC_FUNC_QUAD_X2: + delta = quad_table[prev_state][new_state]; + if (delta == 2) + delta = 0; + gpio_qenc_update_count(priv, delta); + break; + + case GPIO_QENC_FUNC_QUAD_X1: + if (!priv->prev_a && a) { + delta = b ? -1 : 1; + gpio_qenc_update_count(priv, delta); + } + break; + + case GPIO_QENC_FUNC_PULSE_DIR: + if (!priv->prev_a && a) { + delta = b ? -1 : 1; + gpio_qenc_update_count(priv, delta); + } + break; + } + + priv->prev_a = a; + priv->prev_b = b; + + spin_unlock_irqrestore(&priv->lock, flags); + + counter_push_event(counter, COUNTER_EVENT_CHANGE_OF_STATE, 0); + + return IRQ_HANDLED; + +out: + spin_unlock_irqrestore(&priv->lock, flags); + return IRQ_HANDLED; +} + +static irqreturn_t gpio_qenc_b_isr(int irq, void *dev_id) +{ + struct counter_device *counter = dev_id; + struct gpio_qenc_priv *priv = counter_priv(counter); + unsigned long flags; + int a, b, prev_state, new_state, delta; + + spin_lock_irqsave(&priv->lock, flags); + + if (!priv->enabled) + goto out; + + a = gpiod_get_value(priv->gpio_a); + b = gpiod_get_value(priv->gpio_b); + + prev_state = (priv->prev_a << 1) | priv->prev_b; + new_state = (a << 1) | b; + + switch (priv->function) { + case GPIO_QENC_FUNC_QUAD_X4: + delta = quad_table[prev_state][new_state]; + if (delta == 2) + delta = 0; + gpio_qenc_update_count(priv, delta); + break; + + case GPIO_QENC_FUNC_QUAD_X2: + /* X2: only A-channel edges update count */ + break; + + case GPIO_QENC_FUNC_QUAD_X1: + case GPIO_QENC_FUNC_PULSE_DIR: + break; + } + + priv->prev_a = a; + priv->prev_b = b; + + spin_unlock_irqrestore(&priv->lock, flags); + return IRQ_HANDLED; + +out: + spin_unlock_irqrestore(&priv->lock, flags); + return IRQ_HANDLED; +} + +static irqreturn_t gpio_qenc_index_isr(int irq, void *dev_id) +{ + struct counter_device *counter = dev_id; + struct gpio_qenc_priv *priv = counter_priv(counter); + unsigned long flags; + + spin_lock_irqsave(&priv->lock, flags); + + if (priv->enabled && priv->index_enabled) + priv->count = 0; + + spin_unlock_irqrestore(&priv->lock, flags); + + counter_push_event(counter, COUNTER_EVENT_INDEX, 0); + + return IRQ_HANDLED; +} + +static int gpio_qenc_count_read(struct counter_device *counter, + struct counter_count *count, u64 *val) +{ + struct gpio_qenc_priv *priv = counter_priv(counter); + unsigned long flags; + + spin_lock_irqsave(&priv->lock, flags); + *val = (u64)priv->count; + spin_unlock_irqrestore(&priv->lock, flags); + + return 0; +} + +static int gpio_qenc_count_write(struct counter_device *counter, + struct counter_count *count, const u64 val) +{ + struct gpio_qenc_priv *priv = counter_priv(counter); + unsigned long flags; + + spin_lock_irqsave(&priv->lock, flags); + + if (priv->ceiling && val > priv->ceiling) { + spin_unlock_irqrestore(&priv->lock, flags); + return -EINVAL; + } + + priv->count = (s64)val; + spin_unlock_irqrestore(&priv->lock, flags); + + return 0; +} + +static const enum counter_function gpio_qenc_functions[] = { + COUNTER_FUNCTION_QUADRATURE_X1_A, + COUNTER_FUNCTION_QUADRATURE_X2_A, + COUNTER_FUNCTION_QUADRATURE_X4, + COUNTER_FUNCTION_PULSE_DIRECTION, +}; + +static int gpio_qenc_function_read(struct counter_device *counter, + struct counter_count *count, + enum counter_function *function) +{ + struct gpio_qenc_priv *priv = counter_priv(counter); + unsigned long flags; + + spin_lock_irqsave(&priv->lock, flags); + + switch (priv->function) { + case GPIO_QENC_FUNC_QUAD_X1: + *function = COUNTER_FUNCTION_QUADRATURE_X1_A; + break; + case GPIO_QENC_FUNC_QUAD_X2: + *function = COUNTER_FUNCTION_QUADRATURE_X2_A; + break; + case GPIO_QENC_FUNC_QUAD_X4: + *function = COUNTER_FUNCTION_QUADRATURE_X4; + break; + case GPIO_QENC_FUNC_PULSE_DIR: + *function = COUNTER_FUNCTION_PULSE_DIRECTION; + break; + } + + spin_unlock_irqrestore(&priv->lock, flags); + return 0; +} + +static int gpio_qenc_function_write(struct counter_device *counter, + struct counter_count *count, + enum counter_function function) +{ + struct gpio_qenc_priv *priv = counter_priv(counter); + unsigned long flags; + + spin_lock_irqsave(&priv->lock, flags); + + switch (function) { + case COUNTER_FUNCTION_QUADRATURE_X1_A: + priv->function = GPIO_QENC_FUNC_QUAD_X1; + break; + case COUNTER_FUNCTION_QUADRATURE_X2_A: + priv->function = GPIO_QENC_FUNC_QUAD_X2; + break; + case COUNTER_FUNCTION_QUADRATURE_X4: + priv->function = GPIO_QENC_FUNC_QUAD_X4; + break; + case COUNTER_FUNCTION_PULSE_DIRECTION: + priv->function = GPIO_QENC_FUNC_PULSE_DIR; + break; + default: + spin_unlock_irqrestore(&priv->lock, flags); + return -EINVAL; + } + + spin_unlock_irqrestore(&priv->lock, flags); + return 0; +} + +static const enum counter_synapse_action gpio_qenc_synapse_actions[] = { + COUNTER_SYNAPSE_ACTION_BOTH_EDGES, + COUNTER_SYNAPSE_ACTION_RISING_EDGE, + COUNTER_SYNAPSE_ACTION_NONE, +}; + +static int gpio_qenc_action_read(struct counter_device *counter, + struct counter_count *count, + struct counter_synapse *synapse, + enum counter_synapse_action *action) +{ + struct gpio_qenc_priv *priv = counter_priv(counter); + enum gpio_qenc_signal_id signal_id = synapse->signal->id; + + switch (priv->function) { + case GPIO_QENC_FUNC_QUAD_X4: + if (signal_id == GPIO_QENC_SIGNAL_A || + signal_id == GPIO_QENC_SIGNAL_B) + *action = COUNTER_SYNAPSE_ACTION_BOTH_EDGES; + else + *action = COUNTER_SYNAPSE_ACTION_RISING_EDGE; + return 0; + + case GPIO_QENC_FUNC_QUAD_X2: + if (signal_id == GPIO_QENC_SIGNAL_A) + *action = COUNTER_SYNAPSE_ACTION_BOTH_EDGES; + else if (signal_id == GPIO_QENC_SIGNAL_B) + *action = COUNTER_SYNAPSE_ACTION_NONE; + else + *action = COUNTER_SYNAPSE_ACTION_RISING_EDGE; + return 0; + + case GPIO_QENC_FUNC_QUAD_X1: + if (signal_id == GPIO_QENC_SIGNAL_A) + *action = COUNTER_SYNAPSE_ACTION_RISING_EDGE; + else if (signal_id == GPIO_QENC_SIGNAL_B) + *action = COUNTER_SYNAPSE_ACTION_NONE; + else + *action = COUNTER_SYNAPSE_ACTION_RISING_EDGE; + return 0; + + case GPIO_QENC_FUNC_PULSE_DIR: + if (signal_id == GPIO_QENC_SIGNAL_A) + *action = COUNTER_SYNAPSE_ACTION_RISING_EDGE; + else + *action = COUNTER_SYNAPSE_ACTION_NONE; + return 0; + } + + return -EINVAL; +} + +static int gpio_qenc_signal_read(struct counter_device *counter, + struct counter_signal *signal, + enum counter_signal_level *level) +{ + struct gpio_qenc_priv *priv = counter_priv(counter); + struct gpio_desc *gpio; + int ret; + + switch (signal->id) { + case GPIO_QENC_SIGNAL_A: + gpio = priv->gpio_a; + break; + case GPIO_QENC_SIGNAL_B: + gpio = priv->gpio_b; + break; + case GPIO_QENC_SIGNAL_INDEX: + gpio = priv->gpio_index; + break; + default: + return -EINVAL; + } + + if (!gpio) + return -EINVAL; + + ret = gpiod_get_value(gpio); + if (ret < 0) + return ret; + + *level = ret ? COUNTER_SIGNAL_LEVEL_HIGH : COUNTER_SIGNAL_LEVEL_LOW; + return 0; +} + +static int gpio_qenc_events_configure(struct counter_device *counter) +{ + return 0; +} + +static int gpio_qenc_watch_validate(struct counter_device *counter, + const struct counter_watch *watch) +{ + if (watch->channel != 0) + return -EINVAL; + + switch (watch->event) { + case COUNTER_EVENT_CHANGE_OF_STATE: + case COUNTER_EVENT_INDEX: + return 0; + default: + return -EINVAL; + } +} + +static const struct counter_ops gpio_qenc_ops = { + .count_read = gpio_qenc_count_read, + .count_write = gpio_qenc_count_write, + .function_read = gpio_qenc_function_read, + .function_write = gpio_qenc_function_write, + .action_read = gpio_qenc_action_read, + .signal_read = gpio_qenc_signal_read, + .events_configure = gpio_qenc_events_configure, + .watch_validate = gpio_qenc_watch_validate, +}; + +static int gpio_qenc_ceiling_read(struct counter_device *counter, + struct counter_count *count, u64 *val) +{ + struct gpio_qenc_priv *priv = counter_priv(counter); + unsigned long flags; + + spin_lock_irqsave(&priv->lock, flags); + *val = priv->ceiling; + spin_unlock_irqrestore(&priv->lock, flags); + + return 0; +} + +static int gpio_qenc_ceiling_write(struct counter_device *counter, + struct counter_count *count, const u64 val) +{ + struct gpio_qenc_priv *priv = counter_priv(counter); + unsigned long flags; + + spin_lock_irqsave(&priv->lock, flags); + priv->ceiling = val; + spin_unlock_irqrestore(&priv->lock, flags); + + return 0; +} + +static int gpio_qenc_enable_read(struct counter_device *counter, + struct counter_count *count, u8 *enable) +{ + struct gpio_qenc_priv *priv = counter_priv(counter); + + *enable = priv->enabled; + return 0; +} + +static int gpio_qenc_enable_write(struct counter_device *counter, + struct counter_count *count, u8 enable) +{ + struct gpio_qenc_priv *priv = counter_priv(counter); + unsigned long flags; + + spin_lock_irqsave(&priv->lock, flags); + + if (priv->enabled == !!enable) { + spin_unlock_irqrestore(&priv->lock, flags); + return 0; + } + + if (enable) { + priv->enabled = true; + spin_unlock_irqrestore(&priv->lock, flags); + enable_irq(priv->irq_a); + enable_irq(priv->irq_b); + if (priv->irq_index) + enable_irq(priv->irq_index); + } else { + priv->enabled = false; + spin_unlock_irqrestore(&priv->lock, flags); + disable_irq(priv->irq_a); + disable_irq(priv->irq_b); + if (priv->irq_index) + disable_irq(priv->irq_index); + } + + return 0; +} + +static int gpio_qenc_direction_read(struct counter_device *counter, + struct counter_count *count, u32 *direction) +{ + struct gpio_qenc_priv *priv = counter_priv(counter); + unsigned long flags; + + spin_lock_irqsave(&priv->lock, flags); + *direction = priv->direction; + spin_unlock_irqrestore(&priv->lock, flags); + + return 0; +} + +static int gpio_qenc_index_enable_read(struct counter_device *counter, + struct counter_count *count, u8 *val) +{ + struct gpio_qenc_priv *priv = counter_priv(counter); + + *val = priv->index_enabled; + return 0; +} + +static int gpio_qenc_index_enable_write(struct counter_device *counter, + struct counter_count *count, u8 val) +{ + struct gpio_qenc_priv *priv = counter_priv(counter); + unsigned long flags; + + spin_lock_irqsave(&priv->lock, flags); + priv->index_enabled = !!val; + spin_unlock_irqrestore(&priv->lock, flags); + + return 0; +} + +static struct counter_comp gpio_qenc_count_ext[] = { + COUNTER_COMP_CEILING(gpio_qenc_ceiling_read, gpio_qenc_ceiling_write), + COUNTER_COMP_ENABLE(gpio_qenc_enable_read, gpio_qenc_enable_write), + COUNTER_COMP_DIRECTION(gpio_qenc_direction_read), + COUNTER_COMP_COUNT_BOOL("index_enabled", + gpio_qenc_index_enable_read, + gpio_qenc_index_enable_write), +}; + +static int gpio_qenc_probe(struct platform_device *pdev) +{ + struct device *dev = &pdev->dev; + struct counter_device *counter; + struct gpio_qenc_priv *priv; + bool has_index; + int num_signals; + int num_synapses; + int ret; + + counter = devm_counter_alloc(dev, sizeof(*priv)); + if (!counter) + return -ENOMEM; + + priv = counter_priv(counter); + spin_lock_init(&priv->lock); + + priv->gpio_a = devm_gpiod_get(dev, "encoder-a", GPIOD_IN); + if (IS_ERR(priv->gpio_a)) + return dev_err_probe(dev, PTR_ERR(priv->gpio_a), + "failed to get encoder-a GPIO\n"); + + priv->gpio_b = devm_gpiod_get(dev, "encoder-b", GPIOD_IN); + if (IS_ERR(priv->gpio_b)) + return dev_err_probe(dev, PTR_ERR(priv->gpio_b), + "failed to get encoder-b GPIO\n"); + + priv->gpio_index = devm_gpiod_get_optional(dev, "encoder-index", + GPIOD_IN); + if (IS_ERR(priv->gpio_index)) + return dev_err_probe(dev, PTR_ERR(priv->gpio_index), + "failed to get encoder-index GPIO\n"); + + has_index = !!priv->gpio_index; + + priv->irq_a = gpiod_to_irq(priv->gpio_a); + if (priv->irq_a < 0) + return dev_err_probe(dev, priv->irq_a, + "failed to get IRQ for encoder-a\n"); + + priv->irq_b = gpiod_to_irq(priv->gpio_b); + if (priv->irq_b < 0) + return dev_err_probe(dev, priv->irq_b, + "failed to get IRQ for encoder-b\n"); + + if (has_index) { + priv->irq_index = gpiod_to_irq(priv->gpio_index); + if (priv->irq_index < 0) + return dev_err_probe(dev, priv->irq_index, + "failed to get IRQ for encoder-index\n"); + } + + priv->prev_a = gpiod_get_value(priv->gpio_a); + priv->prev_b = gpiod_get_value(priv->gpio_b); + + priv->function = GPIO_QENC_FUNC_QUAD_X4; + priv->direction = COUNTER_COUNT_DIRECTION_FORWARD; + + num_signals = has_index ? 3 : 2; + + priv->signals[GPIO_QENC_SIGNAL_A].id = GPIO_QENC_SIGNAL_A; + priv->signals[GPIO_QENC_SIGNAL_A].name = "Signal A"; + + priv->signals[GPIO_QENC_SIGNAL_B].id = GPIO_QENC_SIGNAL_B; + priv->signals[GPIO_QENC_SIGNAL_B].name = "Signal B"; + + if (has_index) { + priv->signals[GPIO_QENC_SIGNAL_INDEX].id = + GPIO_QENC_SIGNAL_INDEX; + priv->signals[GPIO_QENC_SIGNAL_INDEX].name = "Index"; + } + + num_synapses = num_signals; + + priv->synapses[0].actions_list = gpio_qenc_synapse_actions; + priv->synapses[0].num_actions = ARRAY_SIZE(gpio_qenc_synapse_actions); + priv->synapses[0].signal = &priv->signals[GPIO_QENC_SIGNAL_A]; + + priv->synapses[1].actions_list = gpio_qenc_synapse_actions; + priv->synapses[1].num_actions = ARRAY_SIZE(gpio_qenc_synapse_actions); + priv->synapses[1].signal = &priv->signals[GPIO_QENC_SIGNAL_B]; + + if (has_index) { + priv->synapses[2].actions_list = gpio_qenc_synapse_actions; + priv->synapses[2].num_actions = + ARRAY_SIZE(gpio_qenc_synapse_actions); + priv->synapses[2].signal = + &priv->signals[GPIO_QENC_SIGNAL_INDEX]; + } + + priv->cnts.id = 0; + priv->cnts.name = "Position"; + priv->cnts.functions_list = gpio_qenc_functions; + priv->cnts.num_functions = ARRAY_SIZE(gpio_qenc_functions); + priv->cnts.synapses = priv->synapses; + priv->cnts.num_synapses = num_synapses; + priv->cnts.ext = gpio_qenc_count_ext; + priv->cnts.num_ext = ARRAY_SIZE(gpio_qenc_count_ext); + + counter->name = dev_name(dev); + counter->parent = dev; + counter->ops = &gpio_qenc_ops; + counter->signals = priv->signals; + counter->num_signals = num_signals; + counter->counts = &priv->cnts; + counter->num_counts = 1; + + irq_set_status_flags(priv->irq_a, IRQ_NOAUTOEN); + ret = devm_request_irq(dev, priv->irq_a, gpio_qenc_a_isr, + IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING, + "gpio-qenc-a", counter); + if (ret) + return dev_err_probe(dev, ret, + "failed to request IRQ for encoder-a\n"); + + irq_set_status_flags(priv->irq_b, IRQ_NOAUTOEN); + ret = devm_request_irq(dev, priv->irq_b, gpio_qenc_b_isr, + IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING, + "gpio-qenc-b", counter); + if (ret) + return dev_err_probe(dev, ret, + "failed to request IRQ for encoder-b\n"); + + if (has_index) { + irq_set_status_flags(priv->irq_index, IRQ_NOAUTOEN); + ret = devm_request_irq(dev, priv->irq_index, + gpio_qenc_index_isr, + IRQF_TRIGGER_RISING, + "gpio-qenc-index", counter); + if (ret) + return dev_err_probe(dev, ret, + "failed to request IRQ for encoder-index\n"); + } + + ret = devm_counter_add(dev, counter); + if (ret < 0) + return dev_err_probe(dev, ret, "failed to add counter\n"); + + dev_info(dev, "GPIO quadrature encoder registered (signals: A, B%s)\n", + has_index ? ", Index" : ""); + + return 0; +} + +static const struct of_device_id gpio_qenc_of_match[] = { + { .compatible = "gpio-quadrature-encoder" }, + {} +}; +MODULE_DEVICE_TABLE(of, gpio_qenc_of_match); + +static struct platform_driver gpio_qenc_driver = { + .probe = gpio_qenc_probe, + .driver = { + .name = "gpio-quadrature-encoder", + .of_match_table = gpio_qenc_of_match, + }, +}; +module_platform_driver(gpio_qenc_driver); + +MODULE_ALIAS("platform:gpio-quadrature-encoder"); +MODULE_AUTHOR("Wadim Mueller "); +MODULE_DESCRIPTION("GPIO-based quadrature encoder counter driver"); +MODULE_LICENSE("GPL"); +MODULE_IMPORT_NS("COUNTER"); -- 2.52.0