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
25static DEFINE_SPINLOCK(srmcons_callback_lock);
26static 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
33struct srmcons_private {
34 struct tty_port port;
35 struct timer_list timer;
36} srmcons_singleton;
37
38typedef 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 */
47static int
48srmcons_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, ch: (u8)result.bits.c, flag: 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
67static void
68srmcons_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(lock: &srmcons_callback_lock)) {
77 if (!srmcons_do_receive_chars(port))
78 incr = 100;
79 spin_unlock(lock: &srmcons_callback_lock);
80 }
81
82 spin_lock(lock: &port->lock);
83 if (port->tty)
84 mod_timer(timer: &srmconsp->timer, expires: jiffies + incr);
85 spin_unlock(lock: &port->lock);
86
87 local_irq_restore(flags);
88}
89
90/* called with callback_lock held */
91static void
92srmcons_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
128static ssize_t
129srmcons_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(port: tty->port, buf, count);
135 spin_unlock_irqrestore(lock: &srmcons_callback_lock, flags);
136
137 return count;
138}
139
140static unsigned int
141srmcons_write_room(struct tty_struct *tty)
142{
143 return 512;
144}
145
146static int
147srmcons_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(timer: &srmconsp->timer, expires: jiffies + 10);
160 }
161
162 spin_unlock_irqrestore(lock: &port->lock, flags);
163
164 return 0;
165}
166
167static void
168srmcons_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(timer: &srmconsp->timer);
179 }
180
181 spin_unlock_irqrestore(lock: &port->lock, flags);
182}
183
184
185static struct tty_driver *srmcons_driver;
186
187static 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
194static int __init
195srmcons_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(ptr: driver))
204 return PTR_ERR(ptr: driver);
205
206 tty_port_init(port: &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, op: &srmcons_ops);
216 tty_port_link_device(port: &srmcons_singleton.port, driver, index: 0);
217 err = tty_register_driver(driver);
218 if (err) {
219 tty_driver_kref_put(driver);
220 tty_port_destroy(port: &srmcons_singleton.port);
221 return err;
222 }
223 srmcons_driver = driver;
224 }
225
226 return -ENODEV;
227}
228device_initcall(srmcons_init);
229
230
231/*
232 * The console driver
233 */
234static void
235srm_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, buf: s, count);
241 spin_unlock_irqrestore(lock: &srmcons_callback_lock, flags);
242}
243
244static struct tty_driver *
245srm_console_device(struct console *co, int *index)
246{
247 *index = co->index;
248 return srmcons_driver;
249}
250
251static int
252srm_console_setup(struct console *co, char *options)
253{
254 return 0;
255}
256
257static 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
266void __init
267register_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
276void __init
277unregister_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}
285

source code of linux/arch/alpha/kernel/srmcons.c