1 files changed, 296 insertions, 0 deletions
diff --git a/arch/alpha/kernel/srmcons.c b/arch/alpha/kernel/srmcons.c
new file mode 100644
index 000000000..2b7a314b8
--- /dev/null
+++ b/arch/alpha/kernel/srmcons.c
@@ -0,0 +1,296 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *	linux/arch/alpha/kernel/srmcons.c
+ *
+ * Callback based driver for SRM Console console device.
+ * (TTY driver and console driver)
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/console.h>
+#include <linux/delay.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/timer.h>
+#include <linux/tty.h>
+#include <linux/tty_driver.h>
+#include <linux/tty_flip.h>
+
+#include <asm/console.h>
+#include <linux/uaccess.h>
+
+
+static DEFINE_SPINLOCK(srmcons_callback_lock);
+static int srm_is_registered_console = 0;
+
+/* 
+ * The TTY driver
+ */
+#define MAX_SRM_CONSOLE_DEVICES 1	/* only support 1 console device */
+
+struct srmcons_private {
+	struct tty_port port;
+	struct timer_list timer;
+} srmcons_singleton;
+
+typedef union _srmcons_result {
+	struct {
+		unsigned long c :61;
+		unsigned long status :3;
+	} bits;
+	long as_long;
+} srmcons_result;
+
+/* called with callback_lock held */
+static int
+srmcons_do_receive_chars(struct tty_port *port)
+{
+	srmcons_result result;
+	int count = 0, loops = 0;
+
+	do {
+		result.as_long = callback_getc(0);
+		if (result.bits.status < 2) {
+			tty_insert_flip_char(port, (char)result.bits.c, 0);
+			count++;
+		}
+	} while((result.bits.status & 1) && (++loops < 10));
+
+	if (count)
+		tty_flip_buffer_push(port);
+
+	return count;
+}
+
+static void
+srmcons_receive_chars(struct timer_list *t)
+{
+	struct srmcons_private *srmconsp = from_timer(srmconsp, t, timer);
+	struct tty_port *port = &srmconsp->port;
+	unsigned long flags;
+	int incr = 10;
+
+	local_irq_save(flags);
+	if (spin_trylock(&srmcons_callback_lock)) {
+		if (!srmcons_do_receive_chars(port))
+			incr = 100;
+		spin_unlock(&srmcons_callback_lock);
+	} 
+
+	spin_lock(&port->lock);
+	if (port->tty)
+		mod_timer(&srmconsp->timer, jiffies + incr);
+	spin_unlock(&port->lock);
+
+	local_irq_restore(flags);
+}
+
+/* called with callback_lock held */
+static int
+srmcons_do_write(struct tty_port *port, const char *buf, int count)
+{
+	static char str_cr[1] = "\r";
+	long c, remaining = count;
+	srmcons_result result;
+	char *cur;
+	int need_cr;
+
+	for (cur = (char *)buf; remaining > 0; ) {
+		need_cr = 0;
+		/* 
+		 * Break it up into reasonable size chunks to allow a chance
+		 * for input to get in
+		 */
+		for (c = 0; c < min_t(long, 128L, remaining) && !need_cr; c++)
+			if (cur[c] == '\n')
+				need_cr = 1;
+		
+		while (c > 0) {
+			result.as_long = callback_puts(0, cur, c);
+			c -= result.bits.c;
+			remaining -= result.bits.c;
+			cur += result.bits.c;
+
+			/*
+			 * Check for pending input iff a tty port was provided
+			 */
+			if (port)
+				srmcons_do_receive_chars(port);
+		}
+
+		while (need_cr) {
+			result.as_long = callback_puts(0, str_cr, 1);
+			if (result.bits.c > 0)
+				need_cr = 0;
+		}
+	}
+	return count;
+}
+
+static int
+srmcons_write(struct tty_struct *tty,
+	      const unsigned char *buf, int count)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&srmcons_callback_lock, flags);
+	srmcons_do_write(tty->port, (const char *) buf, count);
+	spin_unlock_irqrestore(&srmcons_callback_lock, flags);
+
+	return count;
+}
+
+static int
+srmcons_write_room(struct tty_struct *tty)
+{
+	return 512;
+}
+
+static int
+srmcons_chars_in_buffer(struct tty_struct *tty)
+{
+	return 0;
+}
+
+static int
+srmcons_open(struct tty_struct *tty, struct file *filp)
+{
+	struct srmcons_private *srmconsp = &srmcons_singleton;
+	struct tty_port *port = &srmconsp->port;
+	unsigned long flags;
+
+	spin_lock_irqsave(&port->lock, flags);
+
+	if (!port->tty) {
+		tty->driver_data = srmconsp;
+		tty->port = port;
+		port->tty = tty; /* XXX proper refcounting */
+		mod_timer(&srmconsp->timer, jiffies + 10);
+	}
+
+	spin_unlock_irqrestore(&port->lock, flags);
+
+	return 0;
+}
+
+static void
+srmcons_close(struct tty_struct *tty, struct file *filp)
+{
+	struct srmcons_private *srmconsp = tty->driver_data;
+	struct tty_port *port = &srmconsp->port;
+	unsigned long flags;
+
+	spin_lock_irqsave(&port->lock, flags);
+
+	if (tty->count == 1) {
+		port->tty = NULL;
+		del_timer(&srmconsp->timer);
+	}
+
+	spin_unlock_irqrestore(&port->lock, flags);
+}
+
+
+static struct tty_driver *srmcons_driver;
+
+static const struct tty_operations srmcons_ops = {
+	.open		= srmcons_open,
+	.close		= srmcons_close,
+	.write		= srmcons_write,
+	.write_room	= srmcons_write_room,
+	.chars_in_buffer= srmcons_chars_in_buffer,
+};
+
+static int __init
+srmcons_init(void)
+{
+	timer_setup(&srmcons_singleton.timer, srmcons_receive_chars, 0);
+	if (srm_is_registered_console) {
+		struct tty_driver *driver;
+		int err;
+
+		driver = alloc_tty_driver(MAX_SRM_CONSOLE_DEVICES);
+		if (!driver)
+			return -ENOMEM;
+
+		tty_port_init(&srmcons_singleton.port);
+
+		driver->driver_name = "srm";
+		driver->name = "srm";
+		driver->major = 0; 	/* dynamic */
+		driver->minor_start = 0;
+		driver->type = TTY_DRIVER_TYPE_SYSTEM;
+		driver->subtype = SYSTEM_TYPE_SYSCONS;
+		driver->init_termios = tty_std_termios;
+		tty_set_operations(driver, &srmcons_ops);
+		tty_port_link_device(&srmcons_singleton.port, driver, 0);
+		err = tty_register_driver(driver);
+		if (err) {
+			put_tty_driver(driver);
+			tty_port_destroy(&srmcons_singleton.port);
+			return err;
+		}
+		srmcons_driver = driver;
+	}
+
+	return -ENODEV;
+}
+device_initcall(srmcons_init);
+
+
+/*
+ * The console driver
+ */
+static void
+srm_console_write(struct console *co, const char *s, unsigned count)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&srmcons_callback_lock, flags);
+	srmcons_do_write(NULL, s, count);
+	spin_unlock_irqrestore(&srmcons_callback_lock, flags);
+}
+
+static struct tty_driver *
+srm_console_device(struct console *co, int *index)
+{
+	*index = co->index;
+	return srmcons_driver;
+}
+
+static int
+srm_console_setup(struct console *co, char *options)
+{
+	return 0;
+}
+
+static struct console srmcons = {
+	.name		= "srm",
+	.write		= srm_console_write,
+	.device		= srm_console_device,
+	.setup		= srm_console_setup,
+	.flags		= CON_PRINTBUFFER | CON_BOOT,
+	.index		= -1,
+};
+
+void __init
+register_srm_console(void)
+{
+	if (!srm_is_registered_console) {
+		callback_open_console();
+		register_console(&srmcons);
+		srm_is_registered_console = 1;
+	}
+}
+
+void __init
+unregister_srm_console(void)
+{
+	if (srm_is_registered_console) {
+		callback_close_console();
+		unregister_console(&srmcons);
+		srm_is_registered_console = 0;
+	}
+}