aboutsummaryrefslogtreecommitdiffstats
path: root/arch/alpha/kernel/srmcons.c
blob: 3b30d4f1fc42d5d438082b82f20a3dee5acad56e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
/*
 *	linux/arch/alpha/kernel/srmcons.c
 *
 * Callback based driver for SRM Console console device.
 * (TTY driver and console driver)
 */

#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/delay.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/timer.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/tty_flip.h>

#include <asm/console.h>
#include <asm/uaccess.h>


static DEFINE_SPINLOCK(srmcons_callback_lock);
static int srm_is_registered_console = 0;

/* 
 * The TTY driver
 */
#define MAX_SRM_CONSOLE_DEVICES 1	/* only support 1 console device */

struct srmcons_private {
	struct tty_struct *tty;
	struct timer_list timer;
	spinlock_t lock;
};

typedef union _srmcons_result {
	struct {
		unsigned long c :61;
		unsigned long status :3;
	} bits;
	long as_long;
} srmcons_result;

/* called with callback_lock held */
static int
srmcons_do_receive_chars(struct tty_struct *tty)
{
	srmcons_result result;
	int count = 0, loops = 0;

	do {
		result.as_long = callback_getc(0);
		if (result.bits.status < 2) {
			tty_insert_flip_char(tty, (char)result.bits.c, 0);
			count++;
		}
	} while((result.bits.status & 1) && (++loops < 10));

	if (count)
		tty_schedule_flip(tty);

	return count;
}

static void
srmcons_receive_chars(unsigned long data)
{
	struct srmcons_private *srmconsp = (struct srmcons_private *)data;
	unsigned long flags;
	int incr = 10;

	local_irq_save(flags);
	if (spin_trylock(&srmcons_callback_lock)) {
		if (!srmcons_do_receive_chars(srmconsp->tty))
			incr = 100;
		spin_unlock(&srmcons_callback_lock);
	} 

	spin_lock(&srmconsp->lock);
	if (srmconsp->tty) {
		srmconsp->timer.expires = jiffies + incr;
		add_timer(&srmconsp->timer);
	}
	spin_unlock(&srmconsp->lock);

	local_irq_restore(flags);
}

/* called with callback_lock held */
static int
srmcons_do_write(struct tty_struct *tty, const char *buf, int count)
{
	static char str_cr[1] = "\r";
	long c, remaining = count;
	srmcons_result result;
	char *cur;
	int need_cr;

	for (cur = (char *)buf; remaining > 0; ) {
		need_cr = 0;
		/* 
		 * Break it up into reasonable size chunks to allow a chance
		 * for input to get in
		 */
		for (c = 0; c < min_t(long, 128L, remaining) && !need_cr; c++)
			if (cur[c] == '\n')
				need_cr = 1;
		
		while (c > 0) {
			result.as_long = callback_puts(0, cur, c);
			c -= result.bits.c;
			remaining -= result.bits.c;
			cur += result.bits.c;

			/*
			 * Check for pending input iff a tty was provided
			 */
			if (tty)
				srmcons_do_receive_chars(tty);
		}

		while (need_cr) {
			result.as_long = callback_puts(0, str_cr, 1);
			if (result.bits.c > 0)
				need_cr = 0;
		}
	}
	return count;
}

static int
srmcons_write(struct tty_struct *tty,
	      const unsigned char *buf, int count)
{
	unsigned long flags;

	spin_lock_irqsave(&srmcons_callback_lock, flags);
	srmcons_do_write(tty, (const char *) buf, count);
	spin_unlock_irqrestore(&srmcons_callback_lock, flags);

	return count;
}

static int
srmcons_write_room(struct tty_struct *tty)
{
	return 512;
}

static int
srmcons_chars_in_buffer(struct tty_struct *tty)
{
	return 0;
}

static int
srmcons_get_private_struct(struct srmcons_private **ps)
{
	static struct srmcons_private *srmconsp = NULL;
	static DEFINE_SPINLOCK(srmconsp_lock);
	unsigned long flags;
	int retval = 0;

	if (srmconsp == NULL) {
		spin_lock_irqsave(&srmconsp_lock, flags);

		srmconsp = kmalloc(sizeof(*srmconsp), GFP_KERNEL);
		if (srmconsp == NULL)
			retval = -ENOMEM;
		else {
			srmconsp->tty = NULL;
			spin_lock_init(&srmconsp->lock);
			init_timer(&srmconsp->timer);
		}

		spin_unlock_irqrestore(&srmconsp_lock, flags);
	}

	*ps = srmconsp;
	return retval;
}

static int
srmcons_open(struct tty_struct *tty, struct file *filp)
{
	struct srmcons_private *srmconsp;
	unsigned long flags;
	int retval;

	retval = srmcons_get_private_struct(&srmconsp);
	if (retval)
		return retval;

	spin_lock_irqsave(&srmconsp->lock, flags);

	if (!srmconsp->tty) {
		tty->driver_data = srmconsp;

		srmconsp->tty = tty;
		srmconsp->timer.function = srmcons_receive_chars;
		srmconsp->timer.data = (unsigned long)srmconsp;
		srmconsp->timer.expires = jiffies + 10;
		add_timer(&srmconsp->timer);
	}

	spin_unlock_irqrestore(&srmconsp->lock, flags);

	return 0;
}

static void
srmcons_close(struct tty_struct *tty, struct file *filp)
{
	struct srmcons_private *srmconsp = tty->driver_data;
	unsigned long flags;

	spin_lock_irqsave(&srmconsp->lock, flags);

	if (tty->count == 1) {
		srmconsp->tty = NULL;
		del_timer(&srmconsp->timer);
	}

	spin_unlock_irqrestore(&srmconsp->lock, flags);
}


static struct tty_driver *srmcons_driver;

static struct tty_operations srmcons_ops = {
	.open		= srmcons_open,
	.close		= srmcons_close,
	.write		= srmcons_write,
	.write_room	= srmcons_write_room,
	.chars_in_buffer= srmcons_chars_in_buffer,
};

static int __init
srmcons_init(void)
{
	if (srm_is_registered_console) {
		struct tty_driver *driver;
		int err;

		driver = alloc_tty_driver(MAX_SRM_CONSOLE_DEVICES);
		if (!driver)
			return -ENOMEM;
		driver->driver_name = "srm";
		driver->name = "srm";
		driver->major = 0; 	/* dynamic */
		driver->minor_start = 0;
		driver->type = TTY_DRIVER_TYPE_SYSTEM;
		driver->subtype = SYSTEM_TYPE_SYSCONS;
		driver->init_termios = tty_std_termios;
		tty_set_operations(driver, &srmcons_ops);
		err = tty_register_driver(driver);
		if (err) {
			put_tty_driver(driver);
			return err;
		}
		srmcons_driver = driver;
	}

	return -ENODEV;
}

module_init(srmcons_init);


/*
 * The console driver
 */
static void
srm_console_write(struct console *co, const char *s, unsigned count)
{
	unsigned long flags;

	spin_lock_irqsave(&srmcons_callback_lock, flags);
	srmcons_do_write(NULL, s, count);
	spin_unlock_irqrestore(&srmcons_callback_lock, flags);
}

static struct tty_driver *
srm_console_device(struct console *co, int *index)
{
	*index = co->index;
	return srmcons_driver;
}

static int __init
srm_console_setup(struct console *co, char *options)
{
	return 0;
}

static struct console srmcons = {
	.name		= "srm",
	.write		= srm_console_write,
	.device		= srm_console_device,
	.setup		= srm_console_setup,
	.flags		= CON_PRINTBUFFER,
	.index		= -1,
};

void __init
register_srm_console(void)
{
	if (!srm_is_registered_console) {
		callback_open_console();
		register_console(&srmcons);
		srm_is_registered_console = 1;
	}
}

void __init
unregister_srm_console(void)
{
	if (srm_is_registered_console) {
		callback_close_console();
		unregister_console(&srmcons);
		srm_is_registered_console = 0;
	}
}