drivers: gpio: Add SDL emulated GPIO support

This commit adds a driver to simulate GPIO state and interrupts
using the keyboard when using SDL.

Signed-off-by: Pieter De Gendt <pieter.degendt@basalte.be>

drivers/gpio/CMakeLists.txt

@@ -38,6 +38,7 @@ zephyr_library_sources_ifdef(CONFIG_GPIO_LPC11U6X   gpio_lpc11u6x.c)
 zephyr_library_sources_ifdef(CONFIG_GPIO_XLNX_AXI   gpio_xlnx_axi.c)
 zephyr_library_sources_ifdef(CONFIG_GPIO_NPCX       gpio_npcx.c)
 zephyr_library_sources_ifdef(CONFIG_GPIO_EMUL       gpio_emul.c)
+zephyr_library_sources_ifdef(CONFIG_GPIO_EMUL_SDL   gpio_emul_sdl.c)
 zephyr_library_sources_ifdef(CONFIG_GPIO_PSOC6      gpio_psoc6.c)
 zephyr_library_sources_ifdef(CONFIG_GPIO_PCAL6408A  gpio_pcal6408a.c)
 zephyr_library_sources_ifdef(CONFIG_GPIO_EOS_S3     gpio_eos_s3.c)

drivers/gpio/Kconfig

@@ -110,6 +110,8 @@ source "drivers/gpio/Kconfig.npcx"
 
 source "drivers/gpio/Kconfig.emul"
 
+source "drivers/gpio/Kconfig.emul_sdl"
+
 source "drivers/gpio/Kconfig.psoc6"
 
 source "drivers/gpio/Kconfig.pcal6408a"

drivers/gpio/Kconfig.emul_sdl

@@ -0,0 +1,13 @@
+# GPIO emulation using SDL keyboard events
+#
+# Copyright (c) 2022, Basalte bv
+# SPDX-License-Identifier: Apache-2.0
+
+config GPIO_EMUL_SDL
+	bool "SDL GPIO emulation"
+	default y
+	depends on DT_HAS_ZEPHYR_GPIO_EMUL_SDL_ENABLED
+	depends on GPIO_EMUL
+	depends on HAS_SDL
+	help
+	  Enable GPIO emulation using SDL keyboard events.

drivers/gpio/gpio_emul_sdl.c

@@ -0,0 +1,103 @@
+/*
+ * Copyright (c) 2022, Basalte bv
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#define DT_DRV_COMPAT zephyr_gpio_emul_sdl
+
+#include <zephyr/drivers/gpio/gpio_emul.h>
+#include <zephyr/logging/log.h>
+
+#include <SDL.h>
+
+LOG_MODULE_REGISTER(gpio_emul_sdl, CONFIG_GPIO_LOG_LEVEL);
+
+struct gpio_sdl_config {
+	const struct device *emul;
+
+	const SDL_Scancode *codes;
+	uint8_t num_codes;
+};
+
+static int sdl_filter(void *arg, SDL_Event *event)
+{
+	const struct device *port = arg;
+	const struct gpio_sdl_config *config = port->config;
+	int ret;
+
+	gpio_pin_t pin = 0;
+
+	/* Only handle keyboard events */
+	switch (event->type) {
+	case SDL_KEYDOWN:
+	case SDL_KEYUP:
+		break;
+	default:
+		return 1;
+	}
+
+	/* Search for the corresponding scancode */
+	while (pin < config->num_codes) {
+		if (config->codes[pin] == event->key.keysym.scancode) {
+			break;
+		}
+		pin++;
+	}
+
+	if (pin == config->num_codes) {
+		/* Not tracked */
+		return 1;
+	}
+
+	/* Lock the scheduler so we can't be preempted,
+	 * as the gpio_emul driver keeps a mutex locked
+	 * for as long as there are pending interrupts
+	 */
+	k_sched_lock();
+
+	/* Update the pin state */
+	ret = gpio_emul_input_set(config->emul, pin, event->type == SDL_KEYDOWN ? 1 : 0);
+
+	k_sched_unlock();
+	if (ret < 0) {
+		LOG_WRN("Failed to emulate input (%d)", ret);
+	}
+
+	return 0;
+}
+
+static int gpio_sdl_init(const struct device *dev)
+{
+	const struct gpio_sdl_config *config = dev->config;
+
+	for (uint8_t pin = 0; pin < config->num_codes; ++pin) {
+		if (config->codes[pin] != SDL_SCANCODE_UNKNOWN) {
+			LOG_INF("GPIO %s:%u = %u", dev->name, pin, config->codes[pin]);
+		}
+	}
+
+	SDL_AddEventWatch(sdl_filter, (void *)dev);
+
+	return 0;
+}
+
+#define GPIO_SDL_DEFINE(inst)								\
+	BUILD_ASSERT(DT_NODE_HAS_COMPAT_STATUS(DT_INST_PARENT(inst),			\
+					       zephyr_gpio_emul, okay),			\
+		     "Enabled parent zephyr,gpio-emul node is required");		\
+											\
+	static const SDL_Scancode gpio_sdl_##inst##_codes[]				\
+		= DT_INST_PROP(inst, scancodes);					\
+											\
+	static const struct gpio_sdl_config gpio_sdl_##inst##_config = {		\
+		.emul = DEVICE_DT_GET(DT_INST_PARENT(inst)),				\
+		.codes = gpio_sdl_##inst##_codes,					\
+		.num_codes = DT_INST_PROP_LEN(inst, scancodes),				\
+	};										\
+											\
+	DEVICE_DT_INST_DEFINE(inst, gpio_sdl_init, NULL, NULL,				\
+			      &gpio_sdl_##inst##_config, POST_KERNEL,			\
+			      CONFIG_GPIO_INIT_PRIORITY, NULL);
+
+DT_INST_FOREACH_STATUS_OKAY(GPIO_SDL_DEFINE)

dts/bindings/gpio/zephyr,gpio-emul-sdl.yaml

@@ -0,0 +1,53 @@
+# Copyright 2022, Basalte bv
+# SPDX-License-Identifier: Apache-2.0
+
+description: |
+  SDL keyboard GPIO input Emulator
+
+  Simulate GPIO state/interrupts using SDL keyboard events. This node has
+  to be a child of a `zephyr,gpio-emul` compatible.
+  Add a list of scancodes for the desired keys to be mapped.
+
+  Refer to https://www.usb.org/sites/default/files/documents/hut1_12v2.pdf
+  section Keyboard/Keypad (p53) for a list of scancode values.
+
+  The following example maps the first 3 numeric keys to GPIO pins:
+
+  /* gpio0 has to be a zephyr,gpio-emul device */
+  &gpio0 {
+    ngpios = <3>;
+
+    sdl_gpio {
+      compatible = "zephyr,gpio-emul-sdl";
+      scancodes = <30 31 32>;
+    };
+  };
+
+  keypad: keypad {
+    compatible = "gpio-keys";
+    key1: key1 {
+      gpios = <&gpio0 0 GPIO_ACTIVE_HIGH>;
+    };
+    key1: key2 {
+      gpios = <&gpio0 1 GPIO_ACTIVE_HIGH>;
+    };
+    key3: key3 {
+      gpios = <&gpio0 2 GPIO_ACTIVE_HIGH>;
+    };
+  };
+
+  The limitations of usage are:
+  - Only active high as we don't get events for keys that aren't pressed
+  - Pressing multiple keys is best effort, state will be kept but no events
+    are generated once the last key is released
+
+compatible: "zephyr,gpio-emul-sdl"
+
+include: base.yaml
+
+properties:
+    scancodes:
+      type: array
+      required: true
+      description: |
+        An array of SDL scancodes mapped to its GPIO index