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 DEFINE_SPINLOCK(memcons_lock);
  29
  30
  31 static size_t write (const char *buf, size_t len)
  32 {
  33         unsigned long 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 struct tty_driver *tty_driver;
  62
  63 static struct tty_driver *memcons_device (struct console *co, int *index)
  64 {
  65         *index = co->index;
  66         return tty_driver;
  67 }
  68
  69 static struct console memcons =
  70 {
  71     .name       = "memcons",
  72     .write      = memcons_write,
  73     .device     = memcons_device,
  74     .flags      = CON_PRINTBUFFER,
  75     .index      = -1,
  76 };
  77
  78 void memcons_setup (void)
  79 {
  80         register_console (&memcons);
  81         printk (KERN_INFO "Console: static memory buffer (memcons)\n");
  82 }
  83 \f
  84 /* Higher level TTY interface.  */
  85
  86 int memcons_tty_open (struct tty_struct *tty, struct file *filp)
  87 {
  88         return 0;
  89 }
  90
  91 int memcons_tty_write (struct tty_struct *tty, const unsigned char *buf, int len)
  92 {
  93         return write (buf, len);
  94 }
  95
  96 int memcons_tty_write_room (struct tty_struct *tty)
  97 {
  98         return &memcons_output_end - (memcons_output + memcons_offs);
  99 }
 100
 101 int memcons_tty_chars_in_buffer (struct tty_struct *tty)
 102 {
 103         /* We have no buffer.  */
 104         return 0;
 105 }
 106
 107 static const struct tty_operations ops = {
 108         .open = memcons_tty_open,
 109         .write = memcons_tty_write,
 110         .write_room = memcons_tty_write_room,
 111         .chars_in_buffer = memcons_tty_chars_in_buffer,
 112 };
 113
 114 int __init memcons_tty_init (void)
 115 {
 116         int err;
 117         struct tty_driver *driver = alloc_tty_driver(1);
 118         if (!driver)
 119                 return -ENOMEM;
 120
 121         driver->name = "memcons";
 122         driver->major = TTY_MAJOR;
 123         driver->minor_start = 64;
 124         driver->type = TTY_DRIVER_TYPE_SYSCONS;
 125         driver->init_termios = tty_std_termios;
 126         tty_set_operations(driver, &ops);
 127         err = tty_register_driver(driver);
 128         if (err) {
 129                 put_tty_driver(driver);
 130                 return err;
 131         }
 132         tty_driver = driver;
 133         return 0;
 134 }
 135 __initcall (memcons_tty_init);