arch/alpha/kernel/srmcons.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *      linux/arch/alpha/kernel/srmcons.c
   4  *
   5  * Callback based driver for SRM Console console device.
   6  * (TTY driver and console driver)
   7  */
   8
   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 <linux/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_port port;
  35         struct timer_list timer;
  36 } srmcons_singleton;
  37
  38 typedef union _srmcons_result {
  39         struct {
  40                 unsigned long c :61;
  41                 unsigned long status :3;
  42         } bits;
  43         long as_long;
  44 } srmcons_result;
  45
  46 /* called with callback_lock held */
  47 static int
  48 srmcons_do_receive_chars(struct tty_port *port)
  49 {
  50         srmcons_result result;
  51         int count = 0, loops = 0;
  52
  53         do {
  54                 result.as_long = callback_getc(0);
  55                 if (result.bits.status < 2) {
  56                         tty_insert_flip_char(port, (char)result.bits.c, 0);
  57                         count++;
  58                 }
  59         } while((result.bits.status & 1) && (++loops < 10));
  60
  61         if (count)
  62                 tty_schedule_flip(port);
  63
  64         return count;
  65 }
  66
  67 static void
  68 srmcons_receive_chars(struct timer_list *t)
  69 {
  70         struct srmcons_private *srmconsp = from_timer(srmconsp, t, timer);
  71         struct tty_port *port = &srmconsp->port;
  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(port))
  78                         incr = 100;
  79                 spin_unlock(&srmcons_callback_lock);
  80         }
  81
  82         spin_lock(&port->lock);
  83         if (port->tty)
  84                 mod_timer(&srmconsp->timer, jiffies + incr);
  85         spin_unlock(&port->lock);
  86
  87         local_irq_restore(flags);
  88 }
  89
  90 /* called with callback_lock held */
  91 static int
  92 srmcons_do_write(struct tty_port *port, const char *buf, int count)
  93 {
  94         static char str_cr[1] = "\r";
  95         long c, remaining = count;
  96         srmcons_result result;
  97         char *cur;
  98         int need_cr;
  99
 100         for (cur = (char *)buf; remaining > 0; ) {
 101                 need_cr = 0;
 102                 /*
 103                  * Break it up into reasonable size chunks to allow a chance
 104                  * for input to get in
 105                  */
 106                 for (c = 0; c < min_t(long, 128L, remaining) && !need_cr; c++)
 107                         if (cur[c] == '\n')
 108                                 need_cr = 1;
 109
 110                 while (c > 0) {
 111                         result.as_long = callback_puts(0, cur, c);
 112                         c -= result.bits.c;
 113                         remaining -= result.bits.c;
 114                         cur += result.bits.c;
 115
 116                         /*
 117                          * Check for pending input iff a tty port was provided
 118                          */
 119                         if (port)
 120                                 srmcons_do_receive_chars(port);
 121                 }
 122
 123                 while (need_cr) {
 124                         result.as_long = callback_puts(0, str_cr, 1);
 125                         if (result.bits.c > 0)
 126                                 need_cr = 0;
 127                 }
 128         }
 129         return count;
 130 }
 131
 132 static int
 133 srmcons_write(struct tty_struct *tty,
 134               const unsigned char *buf, int count)
 135 {
 136         unsigned long flags;
 137
 138         spin_lock_irqsave(&srmcons_callback_lock, flags);
 139         srmcons_do_write(tty->port, (const char *) buf, count);
 140         spin_unlock_irqrestore(&srmcons_callback_lock, flags);
 141
 142         return count;
 143 }
 144
 145 static unsigned int
 146 srmcons_write_room(struct tty_struct *tty)
 147 {
 148         return 512;
 149 }
 150
 151 static int
 152 srmcons_open(struct tty_struct *tty, struct file *filp)
 153 {
 154         struct srmcons_private *srmconsp = &srmcons_singleton;
 155         struct tty_port *port = &srmconsp->port;
 156         unsigned long flags;
 157
 158         spin_lock_irqsave(&port->lock, flags);
 159
 160         if (!port->tty) {
 161                 tty->driver_data = srmconsp;
 162                 tty->port = port;
 163                 port->tty = tty; /* XXX proper refcounting */
 164                 mod_timer(&srmconsp->timer, jiffies + 10);
 165         }
 166
 167         spin_unlock_irqrestore(&port->lock, flags);
 168
 169         return 0;
 170 }
 171
 172 static void
 173 srmcons_close(struct tty_struct *tty, struct file *filp)
 174 {
 175         struct srmcons_private *srmconsp = tty->driver_data;
 176         struct tty_port *port = &srmconsp->port;
 177         unsigned long flags;
 178
 179         spin_lock_irqsave(&port->lock, flags);
 180
 181         if (tty->count == 1) {
 182                 port->tty = NULL;
 183                 del_timer(&srmconsp->timer);
 184         }
 185
 186         spin_unlock_irqrestore(&port->lock, flags);
 187 }
 188
 189
 190 static struct tty_driver *srmcons_driver;
 191
 192 static const struct tty_operations srmcons_ops = {
 193         .open           = srmcons_open,
 194         .close          = srmcons_close,
 195         .write          = srmcons_write,
 196         .write_room     = srmcons_write_room,
 197 };
 198
 199 static int __init
 200 srmcons_init(void)
 201 {
 202         timer_setup(&srmcons_singleton.timer, srmcons_receive_chars, 0);
 203         if (srm_is_registered_console) {
 204                 struct tty_driver *driver;
 205                 int err;
 206
 207                 driver = tty_alloc_driver(MAX_SRM_CONSOLE_DEVICES, 0);
 208                 if (IS_ERR(driver))
 209                         return PTR_ERR(driver);
 210
 211                 tty_port_init(&srmcons_singleton.port);
 212
 213                 driver->driver_name = "srm";
 214                 driver->name = "srm";
 215                 driver->major = 0;      /* dynamic */
 216                 driver->minor_start = 0;
 217                 driver->type = TTY_DRIVER_TYPE_SYSTEM;
 218                 driver->subtype = SYSTEM_TYPE_SYSCONS;
 219                 driver->init_termios = tty_std_termios;
 220                 tty_set_operations(driver, &srmcons_ops);
 221                 tty_port_link_device(&srmcons_singleton.port, driver, 0);
 222                 err = tty_register_driver(driver);
 223                 if (err) {
 224                         tty_driver_kref_put(driver);
 225                         tty_port_destroy(&srmcons_singleton.port);
 226                         return err;
 227                 }
 228                 srmcons_driver = driver;
 229         }
 230
 231         return -ENODEV;
 232 }
 233 device_initcall(srmcons_init);
 234
 235 \f
 236 /*
 237  * The console driver
 238  */
 239 static void
 240 srm_console_write(struct console *co, const char *s, unsigned count)
 241 {
 242         unsigned long flags;
 243
 244         spin_lock_irqsave(&srmcons_callback_lock, flags);
 245         srmcons_do_write(NULL, s, count);
 246         spin_unlock_irqrestore(&srmcons_callback_lock, flags);
 247 }
 248
 249 static struct tty_driver *
 250 srm_console_device(struct console *co, int *index)
 251 {
 252         *index = co->index;
 253         return srmcons_driver;
 254 }
 255
 256 static int
 257 srm_console_setup(struct console *co, char *options)
 258 {
 259         return 0;
 260 }
 261
 262 static struct console srmcons = {
 263         .name           = "srm",
 264         .write          = srm_console_write,
 265         .device         = srm_console_device,
 266         .setup          = srm_console_setup,
 267         .flags          = CON_PRINTBUFFER | CON_BOOT,
 268         .index          = -1,
 269 };
 270
 271 void __init
 272 register_srm_console(void)
 273 {
 274         if (!srm_is_registered_console) {
 275                 callback_open_console();
 276                 register_console(&srmcons);
 277                 srm_is_registered_console = 1;
 278         }
 279 }
 280
 281 void __init
 282 unregister_srm_console(void)
 283 {
 284         if (srm_is_registered_console) {
 285                 callback_close_console();
 286                 unregister_console(&srmcons);
 287                 srm_is_registered_console = 0;
 288         }
 289 }