blob: ff6f5a4b58fb5acd25622ad4fdd1b1a9c45b15f0 [file] [log] [blame]
Rusty Russell31610432007-10-22 11:03:39 +10001/*D:300
2 * The Guest console driver
3 *
4 * Writing console drivers is one of the few remaining Dark Arts in Linux.
5 * Fortunately for us, the path of virtual consoles has been well-trodden by
6 * the PowerPC folks, who wrote "hvc_console.c" to generically support any
7 * virtual console. We use that infrastructure which only requires us to write
8 * the basic put_chars and get_chars functions and call the right register
9 * functions.
10 :*/
11
12/*M:002 The console can be flooded: while the Guest is processing input the
13 * Host can send more. Buffering in the Host could alleviate this, but it is a
14 * difficult problem in general. :*/
15/* Copyright (C) 2006, 2007 Rusty Russell, IBM Corporation
16 *
17 * This program is free software; you can redistribute it and/or modify
18 * it under the terms of the GNU General Public License as published by
19 * the Free Software Foundation; either version 2 of the License, or
20 * (at your option) any later version.
21 *
22 * This program is distributed in the hope that it will be useful,
23 * but WITHOUT ANY WARRANTY; without even the implied warranty of
24 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
25 * GNU General Public License for more details.
26 *
27 * You should have received a copy of the GNU General Public License
28 * along with this program; if not, write to the Free Software
29 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
30 */
31#include <linux/err.h>
32#include <linux/init.h>
33#include <linux/virtio.h>
34#include <linux/virtio_console.h>
35#include "hvc_console.h"
36
37/*D:340 These represent our input and output console queues, and the virtio
38 * operations for them. */
39static struct virtqueue *in_vq, *out_vq;
40static struct virtio_device *vdev;
41
42/* This is our input buffer, and how much data is left in it. */
43static unsigned int in_len;
44static char *in, *inbuf;
45
46/* The operations for our console. */
47static struct hv_ops virtio_cons;
48
Christian Borntraeger91fcad12008-06-20 15:24:15 +020049/* The hvc device */
50static struct hvc_struct *hvc;
51
Rusty Russell31610432007-10-22 11:03:39 +100052/*D:310 The put_chars() callback is pretty straightforward.
53 *
54 * We turn the characters into a scatter-gather list, add it to the output
55 * queue and then kick the Host. Then we sit here waiting for it to finish:
56 * inefficient in theory, but in practice implementations will do it
57 * immediately (lguest's Launcher does). */
58static int put_chars(u32 vtermno, const char *buf, int count)
59{
60 struct scatterlist sg[1];
61 unsigned int len;
62
63 /* This is a convenient routine to initialize a single-elem sg list */
64 sg_init_one(sg, buf, count);
65
66 /* add_buf wants a token to identify this buffer: we hand it any
67 * non-NULL pointer, since there's only ever one buffer. */
68 if (out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, (void *)1) == 0) {
69 /* Tell Host to go! */
70 out_vq->vq_ops->kick(out_vq);
71 /* Chill out until it's done with the buffer. */
72 while (!out_vq->vq_ops->get_buf(out_vq, &len))
73 cpu_relax();
74 }
75
76 /* We're expected to return the amount of data we wrote: all of it. */
77 return count;
78}
79
80/* Create a scatter-gather list representing our input buffer and put it in the
81 * queue. */
82static void add_inbuf(void)
83{
84 struct scatterlist sg[1];
85 sg_init_one(sg, inbuf, PAGE_SIZE);
86
87 /* We should always be able to add one buffer to an empty queue. */
88 if (in_vq->vq_ops->add_buf(in_vq, sg, 0, 1, inbuf) != 0)
89 BUG();
90 in_vq->vq_ops->kick(in_vq);
91}
92
93/*D:350 get_chars() is the callback from the hvc_console infrastructure when
94 * an interrupt is received.
95 *
96 * Most of the code deals with the fact that the hvc_console() infrastructure
97 * only asks us for 16 bytes at a time. We keep in_offset and in_used fields
98 * for partially-filled buffers. */
99static int get_chars(u32 vtermno, char *buf, int count)
100{
101 /* If we don't have an input queue yet, we can't get input. */
102 BUG_ON(!in_vq);
103
104 /* No buffer? Try to get one. */
105 if (!in_len) {
106 in = in_vq->vq_ops->get_buf(in_vq, &in_len);
107 if (!in)
108 return 0;
109 }
110
111 /* You want more than we have to give? Well, try wanting less! */
112 if (in_len < count)
113 count = in_len;
114
115 /* Copy across to their buffer and increment offset. */
116 memcpy(buf, in, count);
117 in += count;
118 in_len -= count;
119
120 /* Finished? Re-register buffer so Host will use it again. */
121 if (in_len == 0)
122 add_inbuf();
123
124 return count;
125}
126/*:*/
127
128/*D:320 Console drivers are initialized very early so boot messages can go out,
129 * so we do things slightly differently from the generic virtio initialization
130 * of the net and block drivers.
131 *
132 * At this stage, the console is output-only. It's too early to set up a
133 * virtqueue, so we let the drivers do some boutique early-output thing. */
134int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int))
135{
136 virtio_cons.put_chars = put_chars;
137 return hvc_instantiate(0, 0, &virtio_cons);
138}
139
Christian Borntraeger91fcad12008-06-20 15:24:15 +0200140/*
Christian Borntraegerc2983452008-11-25 13:36:26 +0100141 * virtio console configuration. This supports:
142 * - console resize
143 */
144static void virtcons_apply_config(struct virtio_device *dev)
145{
146 struct winsize ws;
147
148 if (virtio_has_feature(dev, VIRTIO_CONSOLE_F_SIZE)) {
149 dev->config->get(dev,
150 offsetof(struct virtio_console_config, cols),
151 &ws.ws_col, sizeof(u16));
152 dev->config->get(dev,
153 offsetof(struct virtio_console_config, rows),
154 &ws.ws_row, sizeof(u16));
155 hvc_resize(hvc, ws);
156 }
157}
158
159/*
Christian Borntraeger91fcad12008-06-20 15:24:15 +0200160 * we support only one console, the hvc struct is a global var
Christian Borntraegerc2983452008-11-25 13:36:26 +0100161 * We set the configuration at this point, since we now have a tty
Christian Borntraeger91fcad12008-06-20 15:24:15 +0200162 */
163static int notifier_add_vio(struct hvc_struct *hp, int data)
164{
165 hp->irq_requested = 1;
Christian Borntraegerc2983452008-11-25 13:36:26 +0100166 virtcons_apply_config(vdev);
167
Christian Borntraeger91fcad12008-06-20 15:24:15 +0200168 return 0;
169}
170
171static void notifier_del_vio(struct hvc_struct *hp, int data)
172{
173 hp->irq_requested = 0;
174}
175
176static void hvc_handle_input(struct virtqueue *vq)
177{
178 if (hvc_poll(hvc))
179 hvc_kick();
180}
181
Rusty Russell31610432007-10-22 11:03:39 +1000182/*D:370 Once we're further in boot, we get probed like any other virtio device.
183 * At this stage we set up the output virtqueue.
184 *
185 * To set up and manage our virtual console, we call hvc_alloc(). Since we
186 * never remove the console device we never need this pointer again.
187 *
188 * Finally we put our input buffer in the input queue, ready to receive. */
Randy Dunlap139b8292007-11-05 14:51:01 -0800189static int __devinit virtcons_probe(struct virtio_device *dev)
Rusty Russell31610432007-10-22 11:03:39 +1000190{
191 int err;
Rusty Russell31610432007-10-22 11:03:39 +1000192
193 vdev = dev;
194
195 /* This is the scratch page we use to receive console input */
196 inbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
197 if (!inbuf) {
198 err = -ENOMEM;
199 goto fail;
200 }
201
202 /* Find the input queue. */
203 /* FIXME: This is why we want to wean off hvc: we do nothing
204 * when input comes in. */
Christian Borntraeger91fcad12008-06-20 15:24:15 +0200205 in_vq = vdev->config->find_vq(vdev, 0, hvc_handle_input);
Rusty Russell31610432007-10-22 11:03:39 +1000206 if (IS_ERR(in_vq)) {
207 err = PTR_ERR(in_vq);
208 goto free;
209 }
210
Rusty Russella586d4f2008-02-04 23:49:56 -0500211 out_vq = vdev->config->find_vq(vdev, 1, NULL);
Rusty Russell31610432007-10-22 11:03:39 +1000212 if (IS_ERR(out_vq)) {
213 err = PTR_ERR(out_vq);
214 goto free_in_vq;
215 }
216
217 /* Start using the new console output. */
218 virtio_cons.get_chars = get_chars;
219 virtio_cons.put_chars = put_chars;
Christian Borntraeger91fcad12008-06-20 15:24:15 +0200220 virtio_cons.notifier_add = notifier_add_vio;
221 virtio_cons.notifier_del = notifier_del_vio;
Hendrik Bruecknerfc362e22008-10-13 23:12:48 +0000222 virtio_cons.notifier_hangup = notifier_del_vio;
Rusty Russell31610432007-10-22 11:03:39 +1000223
224 /* The first argument of hvc_alloc() is the virtual console number, so
Christian Borntraeger91fcad12008-06-20 15:24:15 +0200225 * we use zero. The second argument is the parameter for the
226 * notification mechanism (like irq number). We currently leave this
227 * as zero, virtqueues have implicit notifications.
Rusty Russell31610432007-10-22 11:03:39 +1000228 *
229 * The third argument is a "struct hv_ops" containing the put_chars()
Christian Borntraeger91fcad12008-06-20 15:24:15 +0200230 * get_chars(), notifier_add() and notifier_del() pointers.
231 * The final argument is the output buffer size: we can do any size,
232 * so we put PAGE_SIZE here. */
Rusty Russell31610432007-10-22 11:03:39 +1000233 hvc = hvc_alloc(0, 0, &virtio_cons, PAGE_SIZE);
234 if (IS_ERR(hvc)) {
235 err = PTR_ERR(hvc);
236 goto free_out_vq;
237 }
238
239 /* Register the input buffer the first time. */
240 add_inbuf();
241 return 0;
242
243free_out_vq:
244 vdev->config->del_vq(out_vq);
245free_in_vq:
246 vdev->config->del_vq(in_vq);
247free:
248 kfree(inbuf);
249fail:
250 return err;
251}
252
253static struct virtio_device_id id_table[] = {
254 { VIRTIO_ID_CONSOLE, VIRTIO_DEV_ANY_ID },
255 { 0 },
256};
257
Christian Borntraegerc2983452008-11-25 13:36:26 +0100258static unsigned int features[] = {
259 VIRTIO_CONSOLE_F_SIZE,
260};
261
Rusty Russell31610432007-10-22 11:03:39 +1000262static struct virtio_driver virtio_console = {
Christian Borntraegerc2983452008-11-25 13:36:26 +0100263 .feature_table = features,
264 .feature_table_size = ARRAY_SIZE(features),
Rusty Russell31610432007-10-22 11:03:39 +1000265 .driver.name = KBUILD_MODNAME,
266 .driver.owner = THIS_MODULE,
267 .id_table = id_table,
268 .probe = virtcons_probe,
Christian Borntraegerc2983452008-11-25 13:36:26 +0100269 .config_changed = virtcons_apply_config,
Rusty Russell31610432007-10-22 11:03:39 +1000270};
271
272static int __init init(void)
273{
274 return register_virtio_driver(&virtio_console);
275}
276module_init(init);
277
278MODULE_DEVICE_TABLE(virtio, id_table);
279MODULE_DESCRIPTION("Virtio console driver");
280MODULE_LICENSE("GPL");