[ALPHA] New SRM console driver.

From Jeff Wiedemeier:

How about this.. This version no longer piggy backs on ttyS0 (it
actually doesn't touch any files outside arch/alpha/kernel at all). It
does use a dynamic major for the tty piece of the driver. From
userspace, /dev/console is ok for most uses, but because of the 'noctty
= 1' at tty_tio.c:1329 (in the IS_SYSCONS_DEV section) using
/dev/console cannot result in a controlling tty so some things, like
'resize' and bash job control don't work. For those uses, however, it's
easy enough to parse /proc/devices on the way up to get the major number
and create the specific device for the tty side of the driver.

I made a distinction in kernel options as well. "srmcons" specifically
requests the early prints (as before) and "console=srm" requests the
full driver, including the early prints. The two options can be
combined with "console=srm" behavior resulting. The other change is that
if "console=srm" is specified, I don't unregister_srm_console before
console_init any more - that only happens in the "srmcons" case. That
way preferred console selection remains stable and "console=srm" doesn't
result in the early messages being repeated when the driver
re-registers. The use of "srmcons_allowed" is also eliminated due to the
"srmcons" vs. "console=srm" distinction.

arch/alpha/kernel/Makefile

@@ -35,8 +35,13 @@ obj-y    += err_titan.o err_marvel.o
 
 obj-y	 += es1888.o smc37c669.o smc37c93x.o ns87312.o gct.o
 
+obj-y    += srmcons.o
+
 else
 
+# Misc support
+obj-$(CONFIG_ALPHA_SRM)		+= srmcons.o
+
 # Core logic support
 obj-$(CONFIG_ALPHA_APECS)	+= core_apecs.o
 obj-$(CONFIG_ALPHA_CIA)		+= core_cia.o

arch/alpha/kernel/proto.h

@@ -110,8 +110,15 @@ extern unsigned long wildfire_node_mem_size(int);
 extern unsigned long srm_hae;
 extern int boot_cpuid;
 extern int srmcons_output;
+
+/* srmcons.c */
+#if defined(CONFIG_ALPHA_GENERIC) || defined(CONFIG_ALPHA_SRM)
 extern void register_srm_console(void);
 extern void unregister_srm_console(void);
+#else
+#define register_srm_console()
+#define unregister_srm_console()
+#endif
 
 /* smp.c */
 extern void setup_smp(void);

arch/alpha/kernel/setup.c

@@ -82,7 +82,10 @@ int boot_cpuid;
  * called before console_init(), so we put "unregister" code
  * there to prevent schizophrenic console behavior later... ;-}
  *
- * By default, OFF; set it with a bootcommand arg of "srmcons".
+ * By default, OFF; set it with a bootcommand arg of "srmcons" or 
+ * "console=srm". The meaning of these two args is:
+ *     "srmcons"     - early callback prints 
+ *     "console=srm" - full callback based console, including early prints
  */
 int srmcons_output = 0;
 
@@ -464,57 +467,6 @@ page_is_ram(unsigned long pfn)
 #undef PFN_PHYS
 #undef PFN_MAX
 
-#if defined(CONFIG_ALPHA_GENERIC) || defined(CONFIG_ALPHA_SRM)
-/*
- *      Manage the SRM callbacks as a "console".
- */
-static struct console srmcons;
-
-void __init register_srm_console(void)
-{
-        register_console(&srmcons);
-}
-
-void __init unregister_srm_console(void)
-{
-        unregister_console(&srmcons);
-}
-
-static void srm_console_write(struct console *co, const char *s,
-                                unsigned count)
-{
-	srm_printk(s);
-}
-
-static kdev_t srm_console_device(struct console *c)
-{
-	/* Huh? */
-        return mk_kdev(TTY_MAJOR, 64 + c->index);
-}
-
-static int __init srm_console_setup(struct console *co, char *options)
-{
-	return 1;
-}
-
-static struct console srmcons = {
-	.name		= "srm0",
-	.write		= srm_console_write,
-	.device		= srm_console_device,
-	.setup		= srm_console_setup,
-	.flags		= CON_PRINTBUFFER | CON_ENABLED, /* fake it out */
-	.index		= -1,
-};
-
-#else
-void __init register_srm_console(void)
-{
-}
-void __init unregister_srm_console(void)
-{
-}
-#endif
-
 void __init
 setup_arch(char **cmdline_p)
 {
@@ -577,7 +529,11 @@ setup_arch(char **cmdline_p)
 			continue;
 		}
 		if (strncmp(p, "srmcons", 7) == 0) {
-			srmcons_output = 1;
+			srmcons_output |= 1;
+			continue;
+		}
+		if (strncmp(p, "console=srm", 11) == 0) {
+			srmcons_output |= 2;
 			continue;
 		}
 		if (strncmp(p, "gartsize=", 9) == 0) {
@@ -593,6 +549,13 @@ setup_arch(char **cmdline_p)
 	/* If we want SRM console printk echoing early, do it now. */
 	if (alpha_using_srm && srmcons_output) {
 		register_srm_console();
+
+		/*
+		 * If "console=srm" was specified, clear the srmcons_output
+		 * flag now so that time.c won't unregister_srm_console
+		 */
+		if (srmcons_output & 2)
+			srmcons_output = 0;
 	}
 
 #ifdef CONFIG_MAGIC_SYSRQ

arch/alpha/kernel/srmcons.c

+/*
+ *	linux/arch/alpha/kernel/srmcons.c
+ *
+ * Callback based driver for SRM Console console device.
+ * (TTY driver and console driver)
+ */
+
+#include <linux/config.h>
+#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 <asm/uaccess.h>
+
+
+static spinlock_t srmcons_callback_lock = SPIN_LOCK_UNLOCKED;
+static int srm_is_registered_console = 0;
+
+/* 
+ * The TTY driver
+ */
+#define MAX_SRM_CONSOLE_DEVICES 1	/* only support 1 console device */
+
+static int srmcons_refcount;
+static struct tty_struct *srmcons_table[MAX_SRM_CONSOLE_DEVICES];
+static struct termios *srmcons_termios[MAX_SRM_CONSOLE_DEVICES];
+static struct termios *srmcons_termios_locked[MAX_SRM_CONSOLE_DEVICES];
+
+struct srmcons_private {
+	struct tty_struct *tty;
+	struct timer_list timer;
+	spinlock_t lock;
+};
+
+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_struct *tty)
+{
+	srmcons_result result;
+	int count = 0, loops = 0;
+
+	do {
+		result.as_long = callback_getc(0);
+		if (result.bits.status < 2) {
+			tty_insert_flip_char(tty, (char)result.bits.c, 0);
+			count++;
+		}
+	} while((result.bits.status & 1) && (++loops < 10));
+
+	if (count)
+		tty_schedule_flip(tty);
+
+	return count;
+}
+
+static void
+srmcons_receive_chars(unsigned long data)
+{
+	struct srmcons_private *srmconsp = (struct srmcons_private *)data;
+	unsigned long flags;
+	int incr = 10;
+
+	local_irq_save(flags);
+	if (spin_trylock(&srmcons_callback_lock)) {
+		if (!srmcons_do_receive_chars(srmconsp->tty))
+			incr = 100;
+		spin_unlock(&srmcons_callback_lock);
+	} 
+
+	spin_lock(&srmconsp->lock);
+	if (srmconsp->tty) {
+		srmconsp->timer.expires = jiffies + incr;
+		add_timer(&srmconsp->timer);
+	}
+	spin_unlock(&srmconsp->lock);
+
+	local_irq_restore(flags);
+}
+
+/* called with callback_lock held */
+static int
+srmcons_do_write(struct tty_struct *tty, const unsigned char *buf, int count)
+{
+	unsigned char *str_cr = "\r";
+	long c, remaining = count;
+	srmcons_result result;
+	unsigned char *cur;
+	int need_cr;
+
+	for (cur = (unsigned 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 was provided
+			 */
+			if (tty)
+				srmcons_do_receive_chars(tty);
+		}
+
+		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, int from_user,
+	      const unsigned char *buf, int count)
+{
+	unsigned long flags;
+
+	if (from_user) {
+		unsigned char tmp[512];
+		int ret = 0;
+		size_t c;
+
+		while ((c = count) > 0) {
+			if (c > sizeof(tmp))
+				c = sizeof(tmp);
+			
+			c -= copy_from_user(tmp, buf, c);
+
+			if (!c) { 
+				printk("%s: EFAULT (count %d)\n",
+				       __FUNCTION__, count);
+				return -EFAULT;
+			}
+
+			spin_lock_irqsave(&srmcons_callback_lock, flags);
+			srmcons_do_write(tty, tmp, c);
+			spin_unlock_irqrestore(&srmcons_callback_lock, flags);
+
+			buf += c;
+			count -= c;
+			ret += c;
+		}
+
+		return ret;
+	}
+
+	spin_lock_irqsave(&srmcons_callback_lock, flags);
+	srmcons_do_write(tty, 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_get_private_struct(struct srmcons_private **ps)
+{
+	static struct srmcons_private *srmconsp = NULL;
+	static spinlock_t srmconsp_lock = SPIN_LOCK_UNLOCKED;
+	unsigned long flags;
+	int retval = 0;
+
+	spin_lock_irqsave(&srmconsp_lock, flags);
+
+	do {
+		if (srmconsp != NULL) {
+			*ps = srmconsp;
+			break;
+		}
+
+		srmconsp = kmalloc(sizeof(*srmconsp), GFP_KERNEL);
+		if (srmconsp == NULL) {
+			retval = -ENOMEM;
+			break;
+		}
+
+		srmconsp->tty = NULL;
+		srmconsp->lock = SPIN_LOCK_UNLOCKED;
+		init_timer(&srmconsp->timer);
+
+		*ps = srmconsp;
+	} while(0);
+
+	spin_unlock_irqrestore(&srmconsp_lock, flags);
+
+	return retval;
+}
+
+static int
+srmcons_open(struct tty_struct *tty, struct file *filp)
+{
+	struct srmcons_private *srmconsp;
+	unsigned long flags;
+	int retval;
+
+	retval = srmcons_get_private_struct(&srmconsp);
+	if (retval)
+		return retval;
+
+	spin_lock_irqsave(&srmconsp->lock, flags);
+
+	if (!srmconsp->tty) {
+		tty->driver_data = srmconsp;
+
+		srmconsp->tty = tty;
+		srmconsp->timer.function = srmcons_receive_chars;
+		srmconsp->timer.data = (unsigned long)srmconsp;
+		srmconsp->timer.expires = jiffies + 10;
+		add_timer(&srmconsp->timer);
+	}
+
+	spin_unlock_irqrestore(&srmconsp->lock, flags);
+
+	return 0;
+}
+
+static void
+srmcons_close(struct tty_struct *tty, struct file *filp)
+{
+	struct srmcons_private *srmconsp = tty->driver_data;
+	unsigned long flags;
+
+	spin_lock_irqsave(&srmconsp->lock, flags);
+
+	if (tty->count == 1) {
+		srmconsp->tty = NULL;
+		del_timer(&srmconsp->timer);
+	}
+
+	spin_unlock_irqrestore(&srmconsp->lock, flags);
+}
+
+
+static struct tty_driver srmcons_driver = {
+	.driver_name	= "srm",
+	.name		= "srm",
+	.magic		= TTY_DRIVER_MAGIC,
+	.major		= 0, 	/* dynamic */
+	.minor_start	= 0,
+	.num		= MAX_SRM_CONSOLE_DEVICES,
+	.type		= TTY_DRIVER_TYPE_SYSTEM,
+	.subtype	= SYSTEM_TYPE_SYSCONS,
+
+	.table		= srmcons_table,
+	.termios	= srmcons_termios,
+	.termios_locked	= srmcons_termios_locked,
+	.refcount	= &srmcons_refcount,
+
+	.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)
+{
+	if (srm_is_registered_console) {
+		srmcons_driver.init_termios = tty_std_termios;
+		return tty_register_driver(&srmcons_driver);
+	}
+
+	return -ENODEV;
+}
+
+module_init(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 kdev_t
+srm_console_device(struct console *co)
+{
+	return mk_kdev(srmcons_driver.major,
+		       srmcons_driver.minor_start + co->index);
+}
+
+static int __init
+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,
+	.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;
+	}
+}