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_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 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 ssize_t 133 srmcons_write(struct tty_struct *tty, const u8 *buf, size_t count) 134 { 135 unsigned long flags; 136 137 spin_lock_irqsave(&srmcons_callback_lock, flags); 138 srmcons_do_write(tty->port, (const char *) buf, count); 139 spin_unlock_irqrestore(&srmcons_callback_lock, flags); 140 141 return count; 142 } 143 144 static unsigned int 145 srmcons_write_room(struct tty_struct *tty) 146 { 147 return 512; 148 } 149 150 static int 151 srmcons_open(struct tty_struct *tty, struct file *filp) 152 { 153 struct srmcons_private *srmconsp = &srmcons_singleton; 154 struct tty_port *port = &srmconsp->port; 155 unsigned long flags; 156 157 spin_lock_irqsave(&port->lock, flags); 158 159 if (!port->tty) { 160 tty->driver_data = srmconsp; 161 tty->port = port; 162 port->tty = tty; /* XXX proper refcounting */ 163 mod_timer(&srmconsp->timer, jiffies + 10); 164 } 165 166 spin_unlock_irqrestore(&port->lock, flags); 167 168 return 0; 169 } 170 171 static void 172 srmcons_close(struct tty_struct *tty, struct file *filp) 173 { 174 struct srmcons_private *srmconsp = tty->driver_data; 175 struct tty_port *port = &srmconsp->port; 176 unsigned long flags; 177 178 spin_lock_irqsave(&port->lock, flags); 179 180 if (tty->count == 1) { 181 port->tty = NULL; 182 del_timer(&srmconsp->timer); 183 } 184 185 spin_unlock_irqrestore(&port->lock, flags); 186 } 187 188 189 static struct tty_driver *srmcons_driver; 190 191 static const struct tty_operations srmcons_ops = { 192 .open = srmcons_open, 193 .close = srmcons_close, 194 .write = srmcons_write, 195 .write_room = srmcons_write_room, 196 }; 197 198 static int __init 199 srmcons_init(void) 200 { 201 timer_setup(&srmcons_singleton.timer, srmcons_receive_chars, 0); 202 if (srm_is_registered_console) { 203 struct tty_driver *driver; 204 int err; 205 206 driver = tty_alloc_driver(MAX_SRM_CONSOLE_DEVICES, 0); 207 if (IS_ERR(driver)) 208 return PTR_ERR(driver); 209 210 tty_port_init(&srmcons_singleton.port); 211 212 driver->driver_name = "srm"; 213 driver->name = "srm"; 214 driver->major = 0; /* dynamic */ 215 driver->minor_start = 0; 216 driver->type = TTY_DRIVER_TYPE_SYSTEM; 217 driver->subtype = SYSTEM_TYPE_SYSCONS; 218 driver->init_termios = tty_std_termios; 219 tty_set_operations(driver, &srmcons_ops); 220 tty_port_link_device(&srmcons_singleton.port, driver, 0); 221 err = tty_register_driver(driver); 222 if (err) { 223 tty_driver_kref_put(driver); 224 tty_port_destroy(&srmcons_singleton.port); 225 return err; 226 } 227 srmcons_driver = driver; 228 } 229 230 return -ENODEV; 231 } 232 device_initcall(srmcons_init); 233 234 235 /* 236 * The console driver 237 */ 238 static void 239 srm_console_write(struct console *co, const char *s, unsigned count) 240 { 241 unsigned long flags; 242 243 spin_lock_irqsave(&srmcons_callback_lock, flags); 244 srmcons_do_write(NULL, s, count); 245 spin_unlock_irqrestore(&srmcons_callback_lock, flags); 246 } 247 248 static struct tty_driver * 249 srm_console_device(struct console *co, int *index) 250 { 251 *index = co->index; 252 return srmcons_driver; 253 } 254 255 static int 256 srm_console_setup(struct console *co, char *options) 257 { 258 return 0; 259 } 260 261 static struct console srmcons = { 262 .name = "srm", 263 .write = srm_console_write, 264 .device = srm_console_device, 265 .setup = srm_console_setup, 266 .flags = CON_PRINTBUFFER | CON_BOOT, 267 .index = -1, 268 }; 269 270 void __init 271 register_srm_console(void) 272 { 273 if (!srm_is_registered_console) { 274 callback_open_console(); 275 register_console(&srmcons); 276 srm_is_registered_console = 1; 277 } 278 } 279 280 void __init 281 unregister_srm_console(void) 282 { 283 if (srm_is_registered_console) { 284 callback_close_console(); 285 unregister_console(&srmcons); 286 srm_is_registered_console = 0; 287 } 288 } 289