aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/char/virtio_console.c
blob: c74dacfa67950f870dcc4ffd7a71fa18dc915b27 (plain) (blame)
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
/*D:300
 * The Guest console driver
 *
 * Writing console drivers is one of the few remaining Dark Arts in Linux.
 * Fortunately for us, the path of virtual consoles has been well-trodden by
 * the PowerPC folks, who wrote "hvc_console.c" to generically support any
 * virtual console.  We use that infrastructure which only requires us to write
 * the basic put_chars and get_chars functions and call the right register
 * functions.
 :*/

/*M:002 The console can be flooded: while the Guest is processing input the
 * Host can send more.  Buffering in the Host could alleviate this, but it is a
 * difficult problem in general. :*/
/* Copyright (C) 2006, 2007 Rusty Russell, IBM Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
#include <linux/err.h>
#include <linux/init.h>
#include <linux/virtio.h>
#include <linux/virtio_console.h>
#include "hvc_console.h"

/*D:340 These represent our input and output console queues, and the virtio
 * operations for them. */
static struct virtqueue *in_vq, *out_vq;
static struct virtio_device *vdev;

/* This is our input buffer, and how much data is left in it. */
static unsigned int in_len;
static char *in, *inbuf;

/* The operations for our console. */
static struct hv_ops virtio_cons;

/* The hvc device */
static struct hvc_struct *hvc;

/*D:310 The put_chars() callback is pretty straightforward.
 *
 * We turn the characters into a scatter-gather list, add it to the output
 * queue and then kick the Host.  Then we sit here waiting for it to finish:
 * inefficient in theory, but in practice implementations will do it
 * immediately (lguest's Launcher does). */
static int put_chars(u32 vtermno, const char *buf, int count)
{
	struct scatterlist sg[1];
	unsigned int len;

	/* This is a convenient routine to initialize a single-elem sg list */
	sg_init_one(sg, buf, count);

	/* add_buf wants a token to identify this buffer: we hand it any
	 * non-NULL pointer, since there's only ever one buffer. */
	if (out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, (void *)1) == 0) {
		/* Tell Host to go! */
		out_vq->vq_ops->kick(out_vq);
		/* Chill out until it's done with the buffer. */
		while (!out_vq->vq_ops->get_buf(out_vq, &len))
			cpu_relax();
	}

	/* We're expected to return the amount of data we wrote: all of it. */
	return count;
}

/* Create a scatter-gather list representing our input buffer and put it in the
 * queue. */
static void add_inbuf(void)
{
	struct scatterlist sg[1];
	sg_init_one(sg, inbuf, PAGE_SIZE);

	/* We should always be able to add one buffer to an empty queue. */
	if (in_vq->vq_ops->add_buf(in_vq, sg, 0, 1, inbuf) != 0)
		BUG();
	in_vq->vq_ops->kick(in_vq);
}

/*D:350 get_chars() is the callback from the hvc_console infrastructure when
 * an interrupt is received.
 *
 * Most of the code deals with the fact that the hvc_console() infrastructure
 * only asks us for 16 bytes at a time.  We keep in_offset and in_used fields
 * for partially-filled buffers. */
static int get_chars(u32 vtermno, char *buf, int count)
{
	/* If we don't have an input queue yet, we can't get input. */
	BUG_ON(!in_vq);

	/* No buffer?  Try to get one. */
	if (!in_len) {
		in = in_vq->vq_ops->get_buf(in_vq, &in_len);
		if (!in)
			return 0;
	}

	/* You want more than we have to give?  Well, try wanting less! */
	if (in_len < count)
		count = in_len;

	/* Copy across to their buffer and increment offset. */
	memcpy(buf, in, count);
	in += count;
	in_len -= count;

	/* Finished?  Re-register buffer so Host will use it again. */
	if (in_len == 0)
		add_inbuf();

	return count;
}
/*:*/

/*D:320 Console drivers are initialized very early so boot messages can go out,
 * so we do things slightly differently from the generic virtio initialization
 * of the net and block drivers.
 *
 * At this stage, the console is output-only.  It's too early to set up a
 * virtqueue, so we let the drivers do some boutique early-output thing. */
int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int))
{
	virtio_cons.put_chars = put_chars;
	return hvc_instantiate(0, 0, &virtio_cons);
}

/*
 * virtio console configuration. This supports:
 * - console resize
 */
static void virtcons_apply_config(struct virtio_device *dev)
{
	struct winsize ws;

	if (virtio_has_feature(dev, VIRTIO_CONSOLE_F_SIZE)) {
		dev->config->get(dev,
				 offsetof(struct virtio_console_config, cols),
				 &ws.ws_col, sizeof(u16));
		dev->config->get(dev,
				 offsetof(struct virtio_console_config, rows),
				 &ws.ws_row, sizeof(u16));
		hvc_resize(hvc, ws);
	}
}

/*
 * we support only one console, the hvc struct is a global var
 * We set the configuration at this point, since we now have a tty
 */
static int notifier_add_vio(struct hvc_struct *hp, int data)
{
	hp->irq_requested = 1;
	virtcons_apply_config(vdev);

	return 0;
}

static void notifier_del_vio(struct hvc_struct *hp, int data)
{
	hp->irq_requested = 0;
}

static void hvc_handle_input(struct virtqueue *vq)
{
	if (hvc_poll(hvc))
		hvc_kick();
}

/*D:370 Once we're further in boot, we get probed like any other virtio device.
 * At this stage we set up the output virtqueue.
 *
 * To set up and manage our virtual console, we call hvc_alloc().  Since we
 * never remove the console device we never need this pointer again.
 *
 * Finally we put our input buffer in the input queue, ready to receive. */
static int __devinit virtcons_probe(struct virtio_device *dev)
{
	vq_callback_t *callbacks[] = { hvc_handle_input, NULL};
	const char *names[] = { "input", "output" };
	struct virtqueue *vqs[2];
	int err;

	vdev = dev;

	/* This is the scratch page we use to receive console input */
	inbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
	if (!inbuf) {
		err = -ENOMEM;
		goto fail;
	}

	/* Find the queues. */
	/* FIXME: This is why we want to wean off hvc: we do nothing
	 * when input comes in. */
	err = vdev->config->find_vqs(vdev, 2, vqs, callbacks, names);
	if (err)
		goto free;

	in_vq = vqs[0];
	out_vq = vqs[1];

	/* Start using the new console output. */
	virtio_cons.get_chars = get_chars;
	virtio_cons.put_chars = put_chars;
	virtio_cons.notifier_add = notifier_add_vio;
	virtio_cons.notifier_del = notifier_del_vio;
	virtio_cons.notifier_hangup = notifier_del_vio;

	/* The first argument of hvc_alloc() is the virtual console number, so
	 * we use zero.  The second argument is the parameter for the
	 * notification mechanism (like irq number). We currently leave this
	 * as zero, virtqueues have implicit notifications.
	 *
	 * The third argument is a "struct hv_ops" containing the put_chars()
	 * get_chars(), notifier_add() and notifier_del() pointers.
	 * The final argument is the output buffer size: we can do any size,
	 * so we put PAGE_SIZE here. */
	hvc = hvc_alloc(0, 0, &virtio_cons, PAGE_SIZE);
	if (IS_ERR(hvc)) {
		err = PTR_ERR(hvc);
		goto free_vqs;
	}

	/* Register the input buffer the first time. */
	add_inbuf();
	return 0;

free_vqs:
	vdev->config->del_vqs(vdev);
free:
	kfree(inbuf);
fail:
	return err;
}

static struct virtio_device_id id_table[] = {
	{ VIRTIO_ID_CONSOLE, VIRTIO_DEV_ANY_ID },
	{ 0 },
};

static unsigned int features[] = {
	VIRTIO_CONSOLE_F_SIZE,
};

static struct virtio_driver virtio_console = {
	.feature_table = features,
	.feature_table_size = ARRAY_SIZE(features),
	.driver.name =	KBUILD_MODNAME,
	.driver.owner =	THIS_MODULE,
	.id_table =	id_table,
	.probe =	virtcons_probe,
	.config_changed = virtcons_apply_config,
};

static int __init init(void)
{
	return register_virtio_driver(&virtio_console);
}
module_init(init);

MODULE_DEVICE_TABLE(virtio, id_table);
MODULE_DESCRIPTION("Virtio console driver");
MODULE_LICENSE("GPL");