serial: uart_native_pty: IRQ support

Add support for the interrupt-driven API. Interrupts are
emulated using a polling thread.

Signed-off-by: Tim Pambor <tim.pambor@codewrights.de>
Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>

boards/native/native_sim/doc/index.rst

@@ -564,8 +564,7 @@ program ends, one could do:
 
    $ zephyr.exe --uart_attach_uart_cmd='ln -s %s /tmp/somename' ; rm /tmp/somename
 
-This driver supports poll mode or async mode with :kconfig:option:`CONFIG_UART_ASYNC_API`.
-Interrupt mode is not supported.
+This driver supports poll mode, interrupt mode and async mode.
 Neither runtime configuration or line control are supported.
 
 .. _native_tty_uart:

drivers/serial/Kconfig.native_pty

@@ -7,6 +7,7 @@ config UART_NATIVE_PTY
 	depends on (DT_HAS_ZEPHYR_NATIVE_PTY_UART_ENABLED || DT_HAS_ZEPHYR_NATIVE_POSIX_UART_ENABLED)
 	select SERIAL_HAS_DRIVER
 	select SERIAL_SUPPORT_ASYNC
+	select SERIAL_SUPPORT_INTERRUPT
 	help
 	  This enables a PTY based UART driver for the POSIX ARCH with up to 2 UARTs.
 	  For the first UART port, the driver can be configured

drivers/serial/uart_native_pty.c

@@ -16,6 +16,7 @@
 #include <stdbool.h>
 #include <zephyr/drivers/uart.h>
 #include <zephyr/kernel.h>
+#include <zephyr/sys/atomic.h>
 #include <cmdline.h> /* native_sim command line options header */
 #include <posix_native_task.h>
 #include <nsi_host_trampolines.h>
@@ -43,6 +44,7 @@ struct native_pty_status {
 	int out_fd;       /* File descriptor used for output */
 	int in_fd;        /* File descriptor used for input */
 	bool on_stdinout; /* This UART is connected to a PTY and not STDIN/OUT */
+	bool stdin_disconnected;
 
 	bool auto_attach;      /* For PTY, attach a terminal emulator automatically */
 	char *auto_attach_cmd; /* If auto_attach, which command to launch the terminal emulator */
@@ -64,8 +66,24 @@ struct native_pty_status {
 		K_KERNEL_STACK_MEMBER(rx_stack, CONFIG_ARCH_POSIX_RECOMMENDED_STACK_SIZE);
 	} async;
 #endif /* CONFIG_UART_ASYNC_API */
+#ifdef CONFIG_UART_INTERRUPT_DRIVEN
+	struct {
+		bool tx_enabled;
+		bool rx_enabled;
+		uart_irq_callback_user_data_t callback;
+		void *cb_data;
+		char char_store;
+		bool char_ready;
+		atomic_t thread_started;
+		/* Instance-specific IRQ emulation thread. */
+		struct k_thread poll_thread;
+		/* Stack for IRQ emulation thread */
+		K_KERNEL_STACK_MEMBER(poll_stack, CONFIG_ARCH_POSIX_RECOMMENDED_STACK_SIZE);
+	} irq;
+#endif /* CONFIG_UART_INTERRUPT_DRIVEN */
 };
 
+static int np_uart_poll_out_n(struct native_pty_status *d, const unsigned char *buf, size_t len);
 static void np_uart_poll_out(const struct device *dev, unsigned char out_char);
 static int np_uart_poll_in(const struct device *dev, unsigned char *p_char);
 static int np_uart_init(const struct device *dev);
@@ -81,6 +99,22 @@ static int np_uart_rx_enable(const struct device *dev, uint8_t *buf, size_t len,
 static int np_uart_rx_disable(const struct device *dev);
 #endif /* CONFIG_UART_ASYNC_API */
 
+#ifdef CONFIG_UART_INTERRUPT_DRIVEN
+static int np_uart_fifo_fill(const struct device *dev, const uint8_t *tx_data, int size);
+static int np_uart_fifo_read(const struct device *dev, uint8_t *rx_data, const int size);
+static void np_uart_irq_tx_enable(const struct device *dev);
+static void np_uart_irq_tx_disable(const struct device *dev);
+static int np_uart_irq_tx_ready(const struct device *dev);
+static int np_uart_irq_tx_complete(const struct device *dev);
+static void np_uart_irq_rx_enable(const struct device *dev);
+static void np_uart_irq_rx_disable(const struct device *dev);
+static int np_uart_irq_rx_ready(const struct device *dev);
+static int np_uart_irq_is_pending(const struct device *dev);
+static int np_uart_irq_update(const struct device *dev);
+static void np_uart_irq_callback_set(const struct device *dev, uart_irq_callback_user_data_t cb,
+				     void *cb_data);
+#endif /* CONFIG_UART_INTERRUPT_DRIVEN */
+
 static DEVICE_API(uart, np_uart_driver_api) = {
 	.poll_out = np_uart_poll_out,
 	.poll_in = np_uart_poll_in,
@@ -92,6 +126,20 @@ static DEVICE_API(uart, np_uart_driver_api) = {
 	.rx_enable = np_uart_rx_enable,
 	.rx_disable = np_uart_rx_disable,
 #endif /* CONFIG_UART_ASYNC_API */
+#ifdef CONFIG_UART_INTERRUPT_DRIVEN
+	.fifo_fill        = np_uart_fifo_fill,
+	.fifo_read        = np_uart_fifo_read,
+	.irq_tx_enable    = np_uart_irq_tx_enable,
+	.irq_tx_disable	  = np_uart_irq_tx_disable,
+	.irq_tx_ready     = np_uart_irq_tx_ready,
+	.irq_tx_complete  = np_uart_irq_tx_complete,
+	.irq_rx_enable    = np_uart_irq_rx_enable,
+	.irq_rx_disable   = np_uart_irq_rx_disable,
+	.irq_rx_ready     = np_uart_irq_rx_ready,
+	.irq_is_pending   = np_uart_irq_is_pending,
+	.irq_update       = np_uart_irq_update,
+	.irq_callback_set = np_uart_irq_callback_set,
+#endif /* CONFIG_UART_INTERRUPT_DRIVEN */
 };
 
 #define NATIVE_PTY_INSTANCE(inst)                                        \
@@ -162,6 +210,33 @@ static int np_uart_init(const struct device *dev)
 	return 0;
 }
 
+/*
+ * @brief Output len characters towards the serial port
+ *
+ * @param dev UART device struct
+ * @param buf Pointer to the characters to send.
+ * @param len Number of characters to send
+ */
+static int np_uart_poll_out_n(struct native_pty_status *d, const unsigned char *buf, size_t len)
+{
+	int ret;
+
+	if (d->wait_pts) {
+		while (1) {
+			ret = np_uart_slave_connected(d->out_fd);
+
+			if (ret == 1) {
+				break;
+			}
+			k_sleep(K_MSEC(100));
+		}
+	}
+
+	ret = nsi_host_write(d->out_fd, buf, len);
+
+	return ret;
+}
+
 /*
  * @brief Output a character towards the serial port
  *
@@ -170,81 +245,59 @@ static int np_uart_init(const struct device *dev)
  */
 static void np_uart_poll_out(const struct device *dev, unsigned char out_char)
 {
-	int ret;
-	struct native_pty_status *d = (struct native_pty_status *)dev->data;
+	(void)np_uart_poll_out_n((struct native_pty_status *)dev->data, &out_char, 1);
+}
 
-	if (d->wait_pts) {
-		while (1) {
-			int rc = np_uart_slave_connected(d->out_fd);
+/**
+ * @brief Poll the device for up to len input characters
+ *
+ * @param dev UART device structure.
+ * @param p_char Pointer to character.
+ *
+ * @retval > 0 If a character arrived and was stored in p_char
+ * @retval -1 If no character was available to read
+ */
+static int np_uart_read_n(struct native_pty_status *data, unsigned char *p_char, int len)
+{
+	int rc = -1;
+	int in_f = data->in_fd;
 
-			if (rc == 1) {
-				break;
-			}
-			k_sleep(K_MSEC(100));
+	if (len <= 0) {
+		return -1;
+	}
+
+	if (data->on_stdinout) {
+		if (data->stdin_disconnected) {
+			return -1;
 		}
+		rc = np_uart_stdin_read_bottom(in_f, p_char, len);
+
+		if (rc == -2) {
+			data->stdin_disconnected = true;
+			return -1;
+		}
+
+	} else {
+		rc = nsi_host_read(in_f, p_char, len);
 	}
 
-	/* The return value of write() cannot be ignored (there is a warning)
-	 * but we do not need the return value for anything.
-	 */
-	ret = nsi_host_write(d->out_fd, &out_char, 1);
-	(void) ret;
-}
-
-/**
- * @brief Poll the device for input.
- *
- * @param dev UART device structure.
- * @param p_char Pointer to character.
- *
- * @retval 0 If a character arrived and was stored in p_char
- * @retval -1 If no character was available to read
- */
-static int np_uart_stdin_poll_in(const struct device *dev, unsigned char *p_char)
-{
-	int in_f = ((struct native_pty_status *)dev->data)->in_fd;
-	static bool disconnected;
-	int rc;
-
-	if (disconnected == true) {
-		return -1;
+	if (rc > 0) {
+		return rc;
 	}
 
-	rc = np_uart_stdin_poll_in_bottom(in_f, p_char, 1);
-	if (rc == -2) {
-		disconnected = true;
-	}
-	return rc == 1 ? 0 : -1;
-}
-
-/**
- * @brief Poll the device for input.
- *
- * @param dev UART device structure.
- * @param p_char Pointer to character.
- *
- * @retval 0 If a character arrived and was stored in p_char
- * @retval -1 If no character was available to read
- */
-static int np_uart_pty_poll_in(const struct device *dev, unsigned char *p_char)
-{
-	int n = -1;
-	int in_f = ((struct native_pty_status *)dev->data)->in_fd;
-
-	n = nsi_host_read(in_f, p_char, 1);
-	if (n == -1) {
-		return -1;
-	}
-	return 0;
+	return -1;
 }
 
 static int np_uart_poll_in(const struct device *dev, unsigned char *p_char)
 {
-	if (((struct native_pty_status *)dev->data)->on_stdinout) {
-		return np_uart_stdin_poll_in(dev, p_char);
-	} else {
-		return np_uart_pty_poll_in(dev, p_char);
+	struct native_pty_status *data = dev->data;
+
+	int ret = np_uart_read_n(data, p_char, 1);
+
+	if (ret == -1) {
+		return -1;
 	}
+	return 0;
 }
 
 #ifdef CONFIG_UART_ASYNC_API
@@ -337,8 +390,7 @@ static void native_pty_uart_async_poll_function(void *arg1, void *arg2, void *ar
 	ARG_UNUSED(arg3);
 
 	while (data->async.rx_len) {
-		rc = np_uart_stdin_poll_in_bottom(data->in_fd, data->async.rx_buf,
-						  data->async.rx_len);
+		rc = np_uart_read_n(data, data->async.rx_buf, data->async.rx_len);
 		if (rc > 0) {
 			/* Data received */
 			evt.type = UART_RX_RDY;
@@ -403,6 +455,222 @@ static int np_uart_rx_disable(const struct device *dev)
 
 #endif /* CONFIG_UART_ASYNC_API */
 
+#ifdef CONFIG_UART_INTERRUPT_DRIVEN
+static void np_uart_irq_handler(const struct device *dev)
+{
+	struct native_pty_status *data = dev->data;
+
+	if (data->irq.callback) {
+		data->irq.callback(dev, data->irq.cb_data);
+	} else {
+		ERROR("%s: No callback registered\n", __func__);
+	}
+}
+
+static void np_uart_irq_read_1_ahead(struct native_pty_status *data)
+{
+	int ret = np_uart_read_n(data, &data->irq.char_store, 1);
+
+	if (ret == 1) {
+		data->irq.char_ready = true;
+	}
+
+	if (data->stdin_disconnected) {
+		/* There won't be any more data ever */
+		data->irq.rx_enabled = false;
+	}
+}
+
+/*
+ * Emulate uart interrupts using a polling thread
+ */
+static void np_uart_irq_thread(void *arg1, void *arg2, void *arg3)
+{
+	ARG_UNUSED(arg2);
+	ARG_UNUSED(arg3);
+
+	struct device *dev = (struct device *)arg1;
+	struct native_pty_status *data = dev->data;
+
+	while (1) {
+		if (data->irq.rx_enabled) {
+			if (!data->irq.char_ready) {
+				np_uart_irq_read_1_ahead(data);
+			}
+
+			if (data->irq.char_ready) {
+				np_uart_irq_handler(dev);
+			}
+		}
+		if (data->irq.tx_enabled) {
+			np_uart_irq_handler(dev);
+		}
+
+		if ((data->irq.tx_enabled) ||
+		    ((data->irq.rx_enabled) && (data->irq.char_ready))) {
+			/* There is pending work. Let's handle it right away */
+			continue;
+		}
+
+		k_timeout_t wait = K_FOREVER;
+
+		if (data->irq.rx_enabled) {
+			wait = K_MSEC(10);
+		}
+		(void)k_sleep(wait);
+	}
+}
+
+static void np_uart_irq_thread_start(const struct device *dev)
+{
+	struct native_pty_status *data = dev->data;
+
+	/* Create a thread which will wait for data - replacement for IRQ */
+	k_thread_create(&data->irq.poll_thread, data->irq.poll_stack,
+			K_KERNEL_STACK_SIZEOF(data->irq.poll_stack),
+			np_uart_irq_thread,
+			(void *)dev, NULL, NULL,
+			K_HIGHEST_THREAD_PRIO, 0, K_NO_WAIT);
+}
+
+static int np_uart_fifo_fill(const struct device *dev, const uint8_t *tx_data, int size)
+{
+	return np_uart_poll_out_n((struct native_pty_status *)dev->data, tx_data, size);
+}
+
+static int np_uart_fifo_read(const struct device *dev, uint8_t *rx_data, int size)
+{
+	uint32_t len = 0;
+	int ret;
+	struct native_pty_status *data = dev->data;
+
+	if ((size <= 0) || data->stdin_disconnected) {
+		return 0;
+	}
+
+	if (data->irq.char_ready) {
+		rx_data[0] = data->irq.char_store;
+		rx_data++;
+		size--;
+		len = 1;
+		data->irq.char_ready = false;
+		/* Note this native_sim driver code cannot be interrupted,
+		 * so there is no race with np_uart_irq_thread()
+		 */
+	}
+
+	ret = np_uart_read_n(data, rx_data, size);
+
+	if (ret > 0) {
+		len += ret;
+		np_uart_irq_read_1_ahead(data);
+	}
+
+	return len;
+}
+
+static int np_uart_irq_tx_ready(const struct device *dev)
+{
+	struct native_pty_status *data = dev->data;
+
+	return data->irq.tx_enabled ? 1 : 0;
+}
+
+static int np_uart_irq_tx_complete(const struct device *dev)
+{
+	ARG_UNUSED(dev);
+
+	return 1;
+}
+
+static void np_uart_irq_tx_enable(const struct device *dev)
+{
+	struct native_pty_status *data = dev->data;
+
+	bool kick_thread = !data->irq.tx_enabled;
+
+	data->irq.tx_enabled = true;
+
+	if (!atomic_set(&data->irq.thread_started, 1)) {
+		np_uart_irq_thread_start(dev);
+	}
+
+	if (kick_thread) {
+		/* Let's ensure the thread wakes to allow the Tx right away */
+		k_wakeup(&data->irq.poll_thread);
+	}
+}
+
+static void np_uart_irq_tx_disable(const struct device *dev)
+{
+	struct native_pty_status *data = dev->data;
+
+	data->irq.tx_enabled = false;
+}
+
+static void np_uart_irq_rx_enable(const struct device *dev)
+{
+	struct native_pty_status *data = dev->data;
+
+	if (data->stdin_disconnected) {
+		/* There won't ever be data => we ignore the request */
+		return;
+	}
+
+	bool kick_thread = !data->irq.rx_enabled;
+
+	data->irq.rx_enabled = true;
+
+	if (!atomic_set(&data->irq.thread_started, 1)) {
+		np_uart_irq_thread_start(dev);
+	}
+
+	if (kick_thread) {
+		/* Let's ensure the thread wakes to try to check for data */
+		k_wakeup(&data->irq.poll_thread);
+	}
+}
+
+static void np_uart_irq_rx_disable(const struct device *dev)
+{
+	struct native_pty_status *data = dev->data;
+
+	data->irq.rx_enabled = false;
+}
+
+static int np_uart_irq_rx_ready(const struct device *dev)
+{
+	struct native_pty_status *data = dev->data;
+
+	if (data->irq.rx_enabled && data->irq.char_ready) {
+		return 1;
+	}
+	return 0;
+}
+
+static int np_uart_irq_is_pending(const struct device *dev)
+{
+	return np_uart_irq_rx_ready(dev) ||
+		np_uart_irq_tx_ready(dev);
+}
+
+static int np_uart_irq_update(const struct device *dev)
+{
+	ARG_UNUSED(dev);
+
+	return 1;
+}
+
+static void np_uart_irq_callback_set(const struct device *dev, uart_irq_callback_user_data_t cb,
+				     void *cb_data)
+{
+	struct native_pty_status *data = dev->data;
+
+	data->irq.callback = cb;
+	data->irq.cb_data = cb_data;
+}
+#endif /* CONFIG_UART_INTERRUPT_DRIVEN */
+
 
 #define NATIVE_PTY_SET_AUTO_ATTACH_CMD(inst, cmd)      \
 	native_pty_status_##inst.auto_attach_cmd = cmd;

drivers/serial/uart_native_pty_bottom.c

@@ -19,7 +19,7 @@
 #include <string.h>
 #include <pty.h>
 #include <fcntl.h>
-#include <sys/select.h>
+#include <poll.h>
 #include <unistd.h>
 #include <poll.h>
 #include <nsi_tracing.h>
@@ -38,39 +38,35 @@
  * @retval -1 If no character was available to read
  * @retval -2 if the stdin is disconnected
  */
-int np_uart_stdin_poll_in_bottom(int in_f, unsigned char *p_char, int len)
+int np_uart_stdin_read_bottom(int in_f, unsigned char *p_char, int len)
 {
-	if (feof(stdin)) {
-		/*
-		 * The stdinput is fed from a file which finished or the user
-		 * pressed Ctrl+D
-		 */
-		return -2;
-	}
-
 	int n = -1;
-
 	int ready;
-	fd_set readfds;
-	static struct timeval timeout; /* just zero */
 
-	FD_ZERO(&readfds);
-	FD_SET(in_f, &readfds);
+	struct pollfd fds = {.fd = in_f, .events = POLLIN};
 
-	ready = select(in_f+1, &readfds, NULL, NULL, &timeout);
+	ready = poll(&fds, 1, 0);
 
 	if (ready == 0) {
 		return -1;
 	} else if (ready == -1) {
-		ERROR("%s: Error on select ()\n", __func__);
+		ERROR("%s: Error on poll ()\n", __func__);
+	}
+
+	if (len == 0) {
+		return 0;
 	}
 
 	n = read(in_f, p_char, len);
-	if ((n == -1) || (n == 0)) {
-		return -1;
-	}
 
-	return n;
+	if (n == 0) {
+		/* Attempting to read > 0 but getting 0 characters back
+		 * indicates we reached EOF
+		 */
+		return -2;
+	} else {
+		return n;
+	}
 }
 
 /**

drivers/serial/uart_native_pty_bottom.h

@@ -20,7 +20,7 @@ extern "C" {
 
 /* Note: None of these functions are public interfaces. But internal to the native ptty driver */
 
-int np_uart_stdin_poll_in_bottom(int in_f, unsigned char *p_char, int len);
+int np_uart_stdin_read_bottom(int in_f, unsigned char *p_char, int len);
 int np_uart_slave_connected(int fd);
 int np_uart_open_pty(const char *uart_name, const char *auto_attach_cmd,
 		     bool do_auto_attach, bool wait_pts);