arch/alpha/kernel/srmcons.c

   1 /*
   2  *      linux/arch/alpha/kernel/srmcons.c
   3  *
   4  * Callback based driver for SRM Console console device.
   5  * (TTY driver and console driver)
   6  */
   7
   8 #include <linux/config.h>
   9 #include <linux/kernel.h>
  10 #include <linux/init.h>
  11 #include <linux/console.h>
  12 #include <linux/delay.h>
  13 #include <linux/mm.h>
  14 #include <linux/slab.h>
  15 #include <linux/spinlock.h>
  16 #include <linux/timer.h>
  17 #include <linux/tty.h>
  18 #include <linux/tty_driver.h>
  19 #include <linux/tty_flip.h>
  20
  21 #include <asm/console.h>
  22 #include <asm/uaccess.h>
  23
  24
  25 static DEFINE_SPINLOCK(srmcons_callback_lock);
  26 static int srm_is_registered_console = 0;
  27
  28 /*
  29  * The TTY driver
  30  */
  31 #define MAX_SRM_CONSOLE_DEVICES 1       /* only support 1 console device */
  32
  33 struct srmcons_private {
  34         struct tty_struct *tty;
  35         struct timer_list timer;
  36         spinlock_t lock;
  37 };
  38
  39 typedef union _srmcons_result {
  40         struct {
  41                 unsigned long c :61;
  42                 unsigned long status :3;
  43         } bits;
  44         long as_long;
  45 } srmcons_result;
  46
  47 /* called with callback_lock held */
  48 static int
  49 srmcons_do_receive_chars(struct tty_struct *tty)
  50 {
  51         srmcons_result result;
  52         int count = 0, loops = 0;
  53
  54         do {
  55                 result.as_long = callback_getc(0);
  56                 if (result.bits.status < 2) {
  57                         tty_insert_flip_char(tty, (char)result.bits.c, 0);
  58                         count++;
  59                 }
  60         } while((result.bits.status & 1) && (++loops < 10));
  61
  62         if (count)
  63                 tty_schedule_flip(tty);
  64
  65         return count;
  66 }
  67
  68 static void
  69 srmcons_receive_chars(unsigned long data)
  70 {
  71         struct srmcons_private *srmconsp = (struct srmcons_private *)data;
  72         unsigned long flags;
  73         int incr = 10;
  74
  75         local_irq_save(flags);
  76         if (spin_trylock(&srmcons_callback_lock)) {
  77                 if (!srmcons_do_receive_chars(srmconsp->tty))
  78                         incr = 100;
  79                 spin_unlock(&srmcons_callback_lock);
  80         }
  81
  82         spin_lock(&srmconsp->lock);
  83         if (srmconsp->tty) {
  84                 srmconsp->timer.expires = jiffies + incr;
  85                 add_timer(&srmconsp->timer);
  86         }
  87         spin_unlock(&srmconsp->lock);
  88
  89         local_irq_restore(flags);
  90 }
  91
  92 /* called with callback_lock held */
  93 static int
  94 srmcons_do_write(struct tty_struct *tty, const char *buf, int count)
  95 {
  96         static char str_cr[1] = "\r";
  97         long c, remaining = count;
  98         srmcons_result result;
  99         char *cur;
 100         int need_cr;
 101
 102         for (cur = (char *)buf; remaining > 0; ) {
 103                 need_cr = 0;
 104                 /*
 105                  * Break it up into reasonable size chunks to allow a chance
 106                  * for input to get in
 107                  */
 108                 for (c = 0; c < min_t(long, 128L, remaining) && !need_cr; c++)
 109                         if (cur[c] == '\n')
 110                                 need_cr = 1;
 111
 112                 while (c > 0) {
 113                         result.as_long = callback_puts(0, cur, c);
 114                         c -= result.bits.c;
 115                         remaining -= result.bits.c;
 116                         cur += result.bits.c;
 117
 118                         /*
 119                          * Check for pending input iff a tty was provided
 120                          */
 121                         if (tty)
 122                                 srmcons_do_receive_chars(tty);
 123                 }
 124
 125                 while (need_cr) {
 126                         result.as_long = callback_puts(0, str_cr, 1);
 127                         if (result.bits.c > 0)
 128                                 need_cr = 0;
 129                 }
 130         }
 131         return count;
 132 }
 133
 134 static int
 135 srmcons_write(struct tty_struct *tty,
 136               const unsigned char *buf, int count)
 137 {
 138         unsigned long flags;
 139
 140         spin_lock_irqsave(&srmcons_callback_lock, flags);
 141         srmcons_do_write(tty, (const char *) buf, count);
 142         spin_unlock_irqrestore(&srmcons_callback_lock, flags);
 143
 144         return count;
 145 }
 146
 147 static int
 148 srmcons_write_room(struct tty_struct *tty)
 149 {
 150         return 512;
 151 }
 152
 153 static int
 154 srmcons_chars_in_buffer(struct tty_struct *tty)
 155 {
 156         return 0;
 157 }
 158
 159 static int
 160 srmcons_get_private_struct(struct srmcons_private **ps)
 161 {
 162         static struct srmcons_private *srmconsp = NULL;
 163         static DEFINE_SPINLOCK(srmconsp_lock);
 164         unsigned long flags;
 165         int retval = 0;
 166
 167         spin_lock_irqsave(&srmconsp_lock, flags);
 168
 169         do {
 170                 if (srmconsp != NULL) {
 171                         *ps = srmconsp;
 172                         break;
 173                 }
 174
 175                 srmconsp = kmalloc(sizeof(*srmconsp), GFP_KERNEL);
 176                 if (srmconsp == NULL) {
 177                         retval = -ENOMEM;
 178                         break;
 179                 }
 180
 181                 srmconsp->tty = NULL;
 182                 spin_lock_init(&srmconsp->lock);
 183                 init_timer(&srmconsp->timer);
 184
 185                 *ps = srmconsp;
 186         } while(0);
 187
 188         spin_unlock_irqrestore(&srmconsp_lock, flags);
 189
 190         return retval;
 191 }
 192
 193 static int
 194 srmcons_open(struct tty_struct *tty, struct file *filp)
 195 {
 196         struct srmcons_private *srmconsp;
 197         unsigned long flags;
 198         int retval;
 199
 200         retval = srmcons_get_private_struct(&srmconsp);
 201         if (retval)
 202                 return retval;
 203
 204         spin_lock_irqsave(&srmconsp->lock, flags);
 205
 206         if (!srmconsp->tty) {
 207                 tty->driver_data = srmconsp;
 208
 209                 srmconsp->tty = tty;
 210                 srmconsp->timer.function = srmcons_receive_chars;
 211                 srmconsp->timer.data = (unsigned long)srmconsp;
 212                 srmconsp->timer.expires = jiffies + 10;
 213                 add_timer(&srmconsp->timer);
 214         }
 215
 216         spin_unlock_irqrestore(&srmconsp->lock, flags);
 217
 218         return 0;
 219 }
 220
 221 static void
 222 srmcons_close(struct tty_struct *tty, struct file *filp)
 223 {
 224         struct srmcons_private *srmconsp = tty->driver_data;
 225         unsigned long flags;
 226
 227         spin_lock_irqsave(&srmconsp->lock, flags);
 228
 229         if (tty->count == 1) {
 230                 srmconsp->tty = NULL;
 231                 del_timer(&srmconsp->timer);
 232         }
 233
 234         spin_unlock_irqrestore(&srmconsp->lock, flags);
 235 }
 236
 237
 238 static struct tty_driver *srmcons_driver;
 239
 240 static struct tty_operations srmcons_ops = {
 241         .open           = srmcons_open,
 242         .close          = srmcons_close,
 243         .write          = srmcons_write,
 244         .write_room     = srmcons_write_room,
 245         .chars_in_buffer= srmcons_chars_in_buffer,
 246 };
 247
 248 static int __init
 249 srmcons_init(void)
 250 {
 251         if (srm_is_registered_console) {
 252                 struct tty_driver *driver;
 253                 int err;
 254
 255                 driver = alloc_tty_driver(MAX_SRM_CONSOLE_DEVICES);
 256                 if (!driver)
 257                         return -ENOMEM;
 258                 driver->driver_name = "srm";
 259                 driver->name = "srm";
 260                 driver->major = 0;      /* dynamic */
 261                 driver->minor_start = 0;
 262                 driver->type = TTY_DRIVER_TYPE_SYSTEM;
 263                 driver->subtype = SYSTEM_TYPE_SYSCONS;
 264                 driver->init_termios = tty_std_termios;
 265                 tty_set_operations(driver, &srmcons_ops);
 266                 err = tty_register_driver(driver);
 267                 if (err) {
 268                         put_tty_driver(driver);
 269                         return err;
 270                 }
 271                 srmcons_driver = driver;
 272         }
 273
 274         return -ENODEV;
 275 }
 276
 277 module_init(srmcons_init);
 278
 279 \f
 280 /*
 281  * The console driver
 282  */
 283 static void
 284 srm_console_write(struct console *co, const char *s, unsigned count)
 285 {
 286         unsigned long flags;
 287
 288         spin_lock_irqsave(&srmcons_callback_lock, flags);
 289         srmcons_do_write(NULL, s, count);
 290         spin_unlock_irqrestore(&srmcons_callback_lock, flags);
 291 }
 292
 293 static struct tty_driver *
 294 srm_console_device(struct console *co, int *index)
 295 {
 296         *index = co->index;
 297         return srmcons_driver;
 298 }
 299
 300 static int __init
 301 srm_console_setup(struct console *co, char *options)
 302 {
 303         return 0;
 304 }
 305
 306 static struct console srmcons = {
 307         .name           = "srm",
 308         .write          = srm_console_write,
 309         .device         = srm_console_device,
 310         .setup          = srm_console_setup,
 311         .flags          = CON_PRINTBUFFER,
 312         .index          = -1,
 313 };
 314
 315 void __init
 316 register_srm_console(void)
 317 {
 318         if (!srm_is_registered_console) {
 319                 callback_open_console();
 320                 register_console(&srmcons);
 321                 srm_is_registered_console = 1;
 322         }
 323 }
 324
 325 void __init
 326 unregister_srm_console(void)
 327 {
 328         if (srm_is_registered_console) {
 329                 callback_close_console();
 330                 unregister_console(&srmcons);
 331                 srm_is_registered_console = 0;
 332         }
 333 }