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, (u8)result.bits.c, 0);
  57                         count++;
  58                 }
  59         } while((result.bits.status & 1) && (++loops < 10));
  60
  61         if (count)
  62                 tty_flip_buffer_push(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 void
  92 srmcons_do_write(struct tty_port *port, const u8 *buf, size_t count)
  93 {
  94         size_t c;
  95         srmcons_result result;
  96
  97         while (count > 0) {
  98                 bool need_cr = false;
  99                 /*
 100                  * Break it up into reasonable size chunks to allow a chance
 101                  * for input to get in
 102                  */
 103                 for (c = 0; c < min_t(size_t, 128U, count) && !need_cr; c++)
 104                         if (buf[c] == '\n')
 105                                 need_cr = true;
 106
 107                 while (c > 0) {
 108                         result.as_long = callback_puts(0, buf, c);
 109                         c -= result.bits.c;
 110                         count -= result.bits.c;
 111                         buf += result.bits.c;
 112
 113                         /*
 114                          * Check for pending input iff a tty port was provided
 115                          */
 116                         if (port)
 117                                 srmcons_do_receive_chars(port);
 118                 }
 119
 120                 while (need_cr) {
 121                         result.as_long = callback_puts(0, "\r", 1);
 122                         if (result.bits.c > 0)
 123                                 need_cr = false;
 124                 }
 125         }
 126 }
 127
 128 static ssize_t
 129 srmcons_write(struct tty_struct *tty, const u8 *buf, size_t count)
 130 {
 131         unsigned long flags;
 132
 133         spin_lock_irqsave(&srmcons_callback_lock, flags);
 134         srmcons_do_write(tty->port, buf, count);
 135         spin_unlock_irqrestore(&srmcons_callback_lock, flags);
 136
 137         return count;
 138 }
 139
 140 static unsigned int
 141 srmcons_write_room(struct tty_struct *tty)
 142 {
 143         return 512;
 144 }
 145
 146 static int
 147 srmcons_open(struct tty_struct *tty, struct file *filp)
 148 {
 149         struct srmcons_private *srmconsp = &srmcons_singleton;
 150         struct tty_port *port = &srmconsp->port;
 151         unsigned long flags;
 152
 153         spin_lock_irqsave(&port->lock, flags);
 154
 155         if (!port->tty) {
 156                 tty->driver_data = srmconsp;
 157                 tty->port = port;
 158                 port->tty = tty; /* XXX proper refcounting */
 159                 mod_timer(&srmconsp->timer, jiffies + 10);
 160         }
 161
 162         spin_unlock_irqrestore(&port->lock, flags);
 163
 164         return 0;
 165 }
 166
 167 static void
 168 srmcons_close(struct tty_struct *tty, struct file *filp)
 169 {
 170         struct srmcons_private *srmconsp = tty->driver_data;
 171         struct tty_port *port = &srmconsp->port;
 172         unsigned long flags;
 173
 174         spin_lock_irqsave(&port->lock, flags);
 175
 176         if (tty->count == 1) {
 177                 port->tty = NULL;
 178                 del_timer(&srmconsp->timer);
 179         }
 180
 181         spin_unlock_irqrestore(&port->lock, flags);
 182 }
 183
 184
 185 static struct tty_driver *srmcons_driver;
 186
 187 static const struct tty_operations srmcons_ops = {
 188         .open           = srmcons_open,
 189         .close          = srmcons_close,
 190         .write          = srmcons_write,
 191         .write_room     = srmcons_write_room,
 192 };
 193
 194 static int __init
 195 srmcons_init(void)
 196 {
 197         timer_setup(&srmcons_singleton.timer, srmcons_receive_chars, 0);
 198         if (srm_is_registered_console) {
 199                 struct tty_driver *driver;
 200                 int err;
 201
 202                 driver = tty_alloc_driver(MAX_SRM_CONSOLE_DEVICES, 0);
 203                 if (IS_ERR(driver))
 204                         return PTR_ERR(driver);
 205
 206                 tty_port_init(&srmcons_singleton.port);
 207
 208                 driver->driver_name = "srm";
 209                 driver->name = "srm";
 210                 driver->major = 0;      /* dynamic */
 211                 driver->minor_start = 0;
 212                 driver->type = TTY_DRIVER_TYPE_SYSTEM;
 213                 driver->subtype = SYSTEM_TYPE_SYSCONS;
 214                 driver->init_termios = tty_std_termios;
 215                 tty_set_operations(driver, &srmcons_ops);
 216                 tty_port_link_device(&srmcons_singleton.port, driver, 0);
 217                 err = tty_register_driver(driver);
 218                 if (err) {
 219                         tty_driver_kref_put(driver);
 220                         tty_port_destroy(&srmcons_singleton.port);
 221                         return err;
 222                 }
 223                 srmcons_driver = driver;
 224         }
 225
 226         return -ENODEV;
 227 }
 228 device_initcall(srmcons_init);
 229
 230 \f
 231 /*
 232  * The console driver
 233  */
 234 static void
 235 srm_console_write(struct console *co, const char *s, unsigned count)
 236 {
 237         unsigned long flags;
 238
 239         spin_lock_irqsave(&srmcons_callback_lock, flags);
 240         srmcons_do_write(NULL, s, count);
 241         spin_unlock_irqrestore(&srmcons_callback_lock, flags);
 242 }
 243
 244 static struct tty_driver *
 245 srm_console_device(struct console *co, int *index)
 246 {
 247         *index = co->index;
 248         return srmcons_driver;
 249 }
 250
 251 static int
 252 srm_console_setup(struct console *co, char *options)
 253 {
 254         return 0;
 255 }
 256
 257 static struct console srmcons = {
 258         .name           = "srm",
 259         .write          = srm_console_write,
 260         .device         = srm_console_device,
 261         .setup          = srm_console_setup,
 262         .flags          = CON_PRINTBUFFER | CON_BOOT,
 263         .index          = -1,
 264 };
 265
 266 void __init
 267 register_srm_console(void)
 268 {
 269         if (!srm_is_registered_console) {
 270                 callback_open_console();
 271                 register_console(&srmcons);
 272                 srm_is_registered_console = 1;
 273         }
 274 }
 275
 276 void __init
 277 unregister_srm_console(void)
 278 {
 279         if (srm_is_registered_console) {
 280                 callback_close_console();
 281                 unregister_console(&srmcons);
 282                 srm_is_registered_console = 0;
 283         }
 284 }