Linux Device Drivers 3 examples

1 files changed, 291 insertions, 0 deletions

diff --git a/tty/tiny_serial.c b/tty/tiny_serial.c
new file mode 100644
index 0000000..1ae7a43
--- /dev/null
+++ b/tty/tiny_serial.c
@@ -0,0 +1,291 @@
+/*
+ * Tiny Serial driver
+ *
+ * Copyright (C) 2002-2004 Greg Kroah-Hartman (greg@kroah.com)
+ *
+ *	This program is free software; you can redistribute it and/or modify
+ *	it under the terms of the GNU General Public License as published by
+ *	the Free Software Foundation, version 2 of the License.
+ *
+ * This driver shows how to create a minimal serial driver.  It does not rely on
+ * any backing hardware, but creates a timer that emulates data being received
+ * from some kind of hardware.
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+#include <linux/serial.h>
+#include <linux/serial_core.h>
+#include <linux/module.h>
+
+
+#define DRIVER_AUTHOR "Greg Kroah-Hartman <greg@kroah.com>"
+#define DRIVER_DESC "Tiny serial driver"
+
+/* Module information */
+MODULE_AUTHOR( DRIVER_AUTHOR );
+MODULE_DESCRIPTION( DRIVER_DESC );
+MODULE_LICENSE("GPL");
+
+#define DELAY_TIME		HZ * 2	/* 2 seconds per character */
+#define TINY_DATA_CHARACTER	't'
+
+#define TINY_SERIAL_MAJOR	240	/* experimental range */
+#define TINY_SERIAL_MINORS	1	/* only have one minor */
+#define UART_NR			1	/* only use one port */
+
+#define TINY_SERIAL_NAME	"ttytiny"
+
+#define MY_NAME			TINY_SERIAL_NAME
+
+static struct timer_list *timer;
+
+static void tiny_stop_tx(struct uart_port *port, unsigned int tty_stop)
+{
+}
+
+static void tiny_stop_rx(struct uart_port *port)
+{
+}
+
+static void tiny_enable_ms(struct uart_port *port)
+{
+}
+
+static void tiny_tx_chars(struct uart_port *port)
+{
+	struct circ_buf *xmit = &port->info->xmit;
+	int count;
+
+	if (port->x_char) {
+		pr_debug("wrote %2x", port->x_char);
+		port->icount.tx++;
+		port->x_char = 0;
+		return;
+	}
+	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
+		tiny_stop_tx(port, 0);
+		return;
+	}
+
+	count = port->fifosize >> 1;
+	do {
+		pr_debug("wrote %2x", xmit->buf[xmit->tail]);
+		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
+		port->icount.tx++;
+		if (uart_circ_empty(xmit))
+			break;
+	} while (--count > 0);
+
+	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+		uart_write_wakeup(port);
+
+	if (uart_circ_empty(xmit))
+		tiny_stop_tx(port, 0);
+}
+
+static void tiny_start_tx(struct uart_port *port, unsigned int tty_start)
+{
+}
+
+static void tiny_timer(unsigned long data)
+{
+	struct uart_port *port;
+	struct tty_struct *tty;
+
+
+	port = (struct uart_port *)data;
+	if (!port)
+		return;
+	if (!port->info)
+		return;
+	tty = port->info->tty;
+	if (!tty)
+		return;
+
+	/* add one character to the tty port */
+	/* this doesn't actually push the data through unless tty->low_latency is set */
+	tty_insert_flip_char(tty, TINY_DATA_CHARACTER, 0);
+
+	tty_flip_buffer_push(tty);
+
+	/* resubmit the timer again */
+	timer->expires = jiffies + DELAY_TIME;
+	add_timer(timer);
+
+	/* see if we have any data to transmit */
+	tiny_tx_chars(port);
+}
+
+static unsigned int tiny_tx_empty(struct uart_port *port)
+{
+	return 0;
+}
+
+static unsigned int tiny_get_mctrl(struct uart_port *port)
+{
+	return 0;
+}
+
+static void tiny_set_mctrl(struct uart_port *port, unsigned int mctrl)
+{
+}
+
+static void tiny_break_ctl(struct uart_port *port, int break_state)
+{
+}
+
+static void tiny_set_termios(struct uart_port *port,
+			     struct termios *new, struct termios *old)
+{
+	int baud, quot, cflag = new->c_cflag;
+	/* get the byte size */
+	switch (cflag & CSIZE) {
+	case CS5:
+		printk(KERN_DEBUG " - data bits = 5\n");
+		break;
+	case CS6:
+		printk(KERN_DEBUG " - data bits = 6\n");
+		break;
+	case CS7:
+		printk(KERN_DEBUG " - data bits = 7\n");
+		break;
+	default: // CS8
+		printk(KERN_DEBUG " - data bits = 8\n");
+		break;
+	}
+
+	/* determine the parity */
+	if (cflag & PARENB)
+		if (cflag & PARODD)
+			pr_debug(" - parity = odd\n");
+		else
+			pr_debug(" - parity = even\n");
+	else
+		pr_debug(" - parity = none\n");
+
+	/* figure out the stop bits requested */
+	if (cflag & CSTOPB)
+		pr_debug(" - stop bits = 2\n");
+	else
+		pr_debug(" - stop bits = 1\n");
+
+	/* figure out the flow control settings */
+	if (cflag & CRTSCTS)
+		pr_debug(" - RTS/CTS is enabled\n");
+	else
+		pr_debug(" - RTS/CTS is disabled\n");
+
+	/* Set baud rate */
+        baud = uart_get_baud_rate(port, new, old, 0, port->uartclk/16);
+        quot = uart_get_divisor(port, baud);
+	
+	//UART_PUT_DIV_LO(port, (quot & 0xff));
+	//UART_PUT_DIV_HI(port, ((quot & 0xf00) >> 8));
+}
+
+static int tiny_startup(struct uart_port *port)
+{
+	/* this is the first time this port is opened */
+	/* do any hardware initialization needed here */
+
+	/* create our timer and submit it */
+	if (!timer) {
+		timer = kmalloc(sizeof(*timer), GFP_KERNEL);
+		if (!timer)
+			return -ENOMEM;
+	}
+	timer->data = (unsigned long)port;
+	timer->expires = jiffies + DELAY_TIME;
+	timer->function = tiny_timer;
+	add_timer(timer);
+	return 0;
+}
+
+static void tiny_shutdown(struct uart_port *port)
+{
+	/* The port is being closed by the last user. */
+	/* Do any hardware specific stuff here */
+
+	/* shut down our timer */
+	del_timer(timer);
+}
+
+static const char *tiny_type(struct uart_port *port)
+{
+	return "tinytty";
+}
+
+static void tiny_release_port(struct uart_port *port)
+{
+
+}
+
+static int tiny_request_port(struct uart_port *port)
+{
+	return 0;
+}
+
+static void tiny_config_port(struct uart_port *port, int flags)
+{
+}
+
+static int tiny_verify_port(struct uart_port *port, struct serial_struct *ser)
+{
+	return 0;
+}
+
+static struct uart_ops tiny_ops = {
+	.tx_empty	= tiny_tx_empty,
+	.set_mctrl	= tiny_set_mctrl,
+	.get_mctrl	= tiny_get_mctrl,
+	.stop_tx	= tiny_stop_tx,
+	.start_tx	= tiny_start_tx,
+	.stop_rx	= tiny_stop_rx,
+	.enable_ms	= tiny_enable_ms,
+	.break_ctl	= tiny_break_ctl,
+	.startup	= tiny_startup,
+	.shutdown	= tiny_shutdown,
+	.set_termios	= tiny_set_termios,
+	.type		= tiny_type,
+	.release_port	= tiny_release_port,
+	.request_port	= tiny_request_port,
+	.config_port	= tiny_config_port,
+	.verify_port	= tiny_verify_port,
+};
+
+static struct uart_port tiny_port = {
+	.ops		= &tiny_ops,
+};
+
+static struct uart_driver tiny_reg = {
+	.owner		= THIS_MODULE,
+	.driver_name	= TINY_SERIAL_NAME,
+	.dev_name	= TINY_SERIAL_NAME,
+	.major		= TINY_SERIAL_MAJOR,
+	.minor		= TINY_SERIAL_MINORS,
+	.nr		= UART_NR,
+};
+
+static int __init tiny_init(void)
+{
+	int result;
+
+	printk(KERN_INFO "Tiny serial driver loaded\n");
+
+	result = uart_register_driver(&tiny_reg);
+	if (result)
+		return result;
+
+	result = uart_add_one_port(&tiny_reg, &tiny_port);
+	if (result)
+		uart_unregister_driver(&tiny_reg);
+
+	return result;
+}
+
+module_init(tiny_init);