arch/v850/kernel/memcons.c

   1 /*
   2  * arch/v850/kernel/memcons.c -- Console I/O to a memory buffer
   3  *
   4  *  Copyright (C) 2001,02  NEC Corporation
   5  *  Copyright (C) 2001,02  Miles Bader <miles@gnu.org>
   6  *
   7  * This file is subject to the terms and conditions of the GNU General
   8  * Public License.  See the file COPYING in the main directory of this
   9  * archive for more details.
  10  *
  11  * Written by Miles Bader <miles@gnu.org>
  12  */
  13
  14 #include <linux/kernel.h>
  15 #include <linux/console.h>
  16 #include <linux/tty.h>
  17 #include <linux/tty_driver.h>
  18 #include <linux/init.h>
  19
  20 /* If this device is enabled, the linker map should define start and
  21    end points for its buffer. */
  22 extern char memcons_output[], memcons_output_end;
  23
  24 /* Current offset into the buffer.  */
  25 static unsigned long memcons_offs = 0;
  26
  27 /* Spinlock protecting memcons_offs.  */
  28 static spinlock_t memcons_lock = SPIN_LOCK_UNLOCKED;
  29
  30
  31 static size_t write (const char *buf, size_t len)
  32 {
  33         int flags;
  34         char *point;
  35
  36         spin_lock_irqsave (memcons_lock, flags);
  37
  38         point = memcons_output + memcons_offs;
  39         if (point + len >= &memcons_output_end) {
  40                 len = &memcons_output_end - point;
  41                 memcons_offs = 0;
  42         } else
  43                 memcons_offs += len;
  44
  45         spin_unlock_irqrestore (memcons_lock, flags);
  46
  47         memcpy (point, buf, len);
  48
  49         return len;
  50 }
  51
  52 \f
  53 /*  Low-level console. */
  54
  55 static void memcons_write (struct console *co, const char *buf, unsigned len)
  56 {
  57         while (len > 0)
  58                 len -= write (buf, len);
  59 }
  60
  61 static kdev_t memcons_device (struct console *co)
  62 {
  63         return MKDEV (TTY_MAJOR, 64 + co->index);
  64 }
  65
  66 static struct console memcons =
  67 {
  68     .name       = "memcons",
  69     .write      = memcons_write,
  70     .device     = memcons_device,
  71     .flags      = CON_PRINTBUFFER,
  72     .index      = -1,
  73 };
  74
  75 void memcons_setup (void)
  76 {
  77         register_console (&memcons);
  78         printk (KERN_INFO "Console: static memory buffer (memcons)\n");
  79 }
  80 \f
  81 /* Higher level TTY interface.  */
  82
  83 static struct tty_struct *tty_table[1] = { 0 };
  84 static struct termios *tty_termios[1] = { 0 };
  85 static struct termios *tty_termios_locked[1] = { 0 };
  86 static struct tty_driver tty_driver = { 0 };
  87 static int tty_ref_count = 0;
  88
  89 int memcons_tty_open (struct tty_struct *tty, struct file *filp)
  90 {
  91         return 0;
  92 }
  93
  94 int memcons_tty_write (struct tty_struct *tty, int from_user,
  95                        const unsigned char *buf, int len)
  96 {
  97         return write (buf, len);
  98 }
  99
 100 int memcons_tty_write_room (struct tty_struct *tty)
 101 {
 102         return &memcons_output_end - (memcons_output + memcons_offs);
 103 }
 104
 105 int memcons_tty_chars_in_buffer (struct tty_struct *tty)
 106 {
 107         /* We have no buffer.  */
 108         return 0;
 109 }
 110
 111 int __init memcons_tty_init (void)
 112 {
 113         tty_driver.name = "memcons";
 114         tty_driver.major = TTY_MAJOR;
 115         tty_driver.minor_start = 64;
 116         tty_driver.num = 1;
 117         tty_driver.type = TTY_DRIVER_TYPE_SYSCONS;
 118
 119         tty_driver.refcount = &tty_ref_count;
 120
 121         tty_driver.table = tty_table;
 122         tty_driver.termios = tty_termios;
 123         tty_driver.termios_locked = tty_termios_locked;
 124
 125         tty_driver.init_termios = tty_std_termios;
 126
 127         tty_driver.open = memcons_tty_open;
 128         tty_driver.write = memcons_tty_write;
 129         tty_driver.write_room = memcons_tty_write_room;
 130         tty_driver.chars_in_buffer = memcons_tty_chars_in_buffer;
 131
 132         tty_register_driver (&tty_driver);
 133 }
 134 __initcall (memcons_tty_init);