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31610434 RR |
1 | /*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. */ | |
39 | static struct virtqueue *in_vq, *out_vq; | |
40 | static struct virtio_device *vdev; | |
41 | ||
42 | /* This is our input buffer, and how much data is left in it. */ | |
43 | static unsigned int in_len; | |
44 | static char *in, *inbuf; | |
45 | ||
46 | /* The operations for our console. */ | |
47 | static struct hv_ops virtio_cons; | |
48 | ||
49 | /*D:310 The put_chars() callback is pretty straightforward. | |
50 | * | |
51 | * We turn the characters into a scatter-gather list, add it to the output | |
52 | * queue and then kick the Host. Then we sit here waiting for it to finish: | |
53 | * inefficient in theory, but in practice implementations will do it | |
54 | * immediately (lguest's Launcher does). */ | |
55 | static int put_chars(u32 vtermno, const char *buf, int count) | |
56 | { | |
57 | struct scatterlist sg[1]; | |
58 | unsigned int len; | |
59 | ||
60 | /* This is a convenient routine to initialize a single-elem sg list */ | |
61 | sg_init_one(sg, buf, count); | |
62 | ||
63 | /* add_buf wants a token to identify this buffer: we hand it any | |
64 | * non-NULL pointer, since there's only ever one buffer. */ | |
65 | if (out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, (void *)1) == 0) { | |
66 | /* Tell Host to go! */ | |
67 | out_vq->vq_ops->kick(out_vq); | |
68 | /* Chill out until it's done with the buffer. */ | |
69 | while (!out_vq->vq_ops->get_buf(out_vq, &len)) | |
70 | cpu_relax(); | |
71 | } | |
72 | ||
73 | /* We're expected to return the amount of data we wrote: all of it. */ | |
74 | return count; | |
75 | } | |
76 | ||
77 | /* Create a scatter-gather list representing our input buffer and put it in the | |
78 | * queue. */ | |
79 | static void add_inbuf(void) | |
80 | { | |
81 | struct scatterlist sg[1]; | |
82 | sg_init_one(sg, inbuf, PAGE_SIZE); | |
83 | ||
84 | /* We should always be able to add one buffer to an empty queue. */ | |
85 | if (in_vq->vq_ops->add_buf(in_vq, sg, 0, 1, inbuf) != 0) | |
86 | BUG(); | |
87 | in_vq->vq_ops->kick(in_vq); | |
88 | } | |
89 | ||
90 | /*D:350 get_chars() is the callback from the hvc_console infrastructure when | |
91 | * an interrupt is received. | |
92 | * | |
93 | * Most of the code deals with the fact that the hvc_console() infrastructure | |
94 | * only asks us for 16 bytes at a time. We keep in_offset and in_used fields | |
95 | * for partially-filled buffers. */ | |
96 | static int get_chars(u32 vtermno, char *buf, int count) | |
97 | { | |
98 | /* If we don't have an input queue yet, we can't get input. */ | |
99 | BUG_ON(!in_vq); | |
100 | ||
101 | /* No buffer? Try to get one. */ | |
102 | if (!in_len) { | |
103 | in = in_vq->vq_ops->get_buf(in_vq, &in_len); | |
104 | if (!in) | |
105 | return 0; | |
106 | } | |
107 | ||
108 | /* You want more than we have to give? Well, try wanting less! */ | |
109 | if (in_len < count) | |
110 | count = in_len; | |
111 | ||
112 | /* Copy across to their buffer and increment offset. */ | |
113 | memcpy(buf, in, count); | |
114 | in += count; | |
115 | in_len -= count; | |
116 | ||
117 | /* Finished? Re-register buffer so Host will use it again. */ | |
118 | if (in_len == 0) | |
119 | add_inbuf(); | |
120 | ||
121 | return count; | |
122 | } | |
123 | /*:*/ | |
124 | ||
125 | /*D:320 Console drivers are initialized very early so boot messages can go out, | |
126 | * so we do things slightly differently from the generic virtio initialization | |
127 | * of the net and block drivers. | |
128 | * | |
129 | * At this stage, the console is output-only. It's too early to set up a | |
130 | * virtqueue, so we let the drivers do some boutique early-output thing. */ | |
131 | int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int)) | |
132 | { | |
133 | virtio_cons.put_chars = put_chars; | |
134 | return hvc_instantiate(0, 0, &virtio_cons); | |
135 | } | |
136 | ||
137 | /*D:370 Once we're further in boot, we get probed like any other virtio device. | |
138 | * At this stage we set up the output virtqueue. | |
139 | * | |
140 | * To set up and manage our virtual console, we call hvc_alloc(). Since we | |
141 | * never remove the console device we never need this pointer again. | |
142 | * | |
143 | * Finally we put our input buffer in the input queue, ready to receive. */ | |
144 | static int virtcons_probe(struct virtio_device *dev) | |
145 | { | |
146 | int err; | |
147 | struct hvc_struct *hvc; | |
148 | ||
149 | vdev = dev; | |
150 | ||
151 | /* This is the scratch page we use to receive console input */ | |
152 | inbuf = kmalloc(PAGE_SIZE, GFP_KERNEL); | |
153 | if (!inbuf) { | |
154 | err = -ENOMEM; | |
155 | goto fail; | |
156 | } | |
157 | ||
158 | /* Find the input queue. */ | |
159 | /* FIXME: This is why we want to wean off hvc: we do nothing | |
160 | * when input comes in. */ | |
161 | in_vq = vdev->config->find_vq(vdev, NULL); | |
162 | if (IS_ERR(in_vq)) { | |
163 | err = PTR_ERR(in_vq); | |
164 | goto free; | |
165 | } | |
166 | ||
167 | out_vq = vdev->config->find_vq(vdev, NULL); | |
168 | if (IS_ERR(out_vq)) { | |
169 | err = PTR_ERR(out_vq); | |
170 | goto free_in_vq; | |
171 | } | |
172 | ||
173 | /* Start using the new console output. */ | |
174 | virtio_cons.get_chars = get_chars; | |
175 | virtio_cons.put_chars = put_chars; | |
176 | ||
177 | /* The first argument of hvc_alloc() is the virtual console number, so | |
178 | * we use zero. The second argument is the interrupt number; we | |
179 | * currently leave this as zero: it would be better not to use the | |
180 | * hvc mechanism and fix this (FIXME!). | |
181 | * | |
182 | * The third argument is a "struct hv_ops" containing the put_chars() | |
183 | * and get_chars() pointers. The final argument is the output buffer | |
184 | * size: we can do any size, so we put PAGE_SIZE here. */ | |
185 | hvc = hvc_alloc(0, 0, &virtio_cons, PAGE_SIZE); | |
186 | if (IS_ERR(hvc)) { | |
187 | err = PTR_ERR(hvc); | |
188 | goto free_out_vq; | |
189 | } | |
190 | ||
191 | /* Register the input buffer the first time. */ | |
192 | add_inbuf(); | |
193 | return 0; | |
194 | ||
195 | free_out_vq: | |
196 | vdev->config->del_vq(out_vq); | |
197 | free_in_vq: | |
198 | vdev->config->del_vq(in_vq); | |
199 | free: | |
200 | kfree(inbuf); | |
201 | fail: | |
202 | return err; | |
203 | } | |
204 | ||
205 | static struct virtio_device_id id_table[] = { | |
206 | { VIRTIO_ID_CONSOLE, VIRTIO_DEV_ANY_ID }, | |
207 | { 0 }, | |
208 | }; | |
209 | ||
210 | static struct virtio_driver virtio_console = { | |
211 | .driver.name = KBUILD_MODNAME, | |
212 | .driver.owner = THIS_MODULE, | |
213 | .id_table = id_table, | |
214 | .probe = virtcons_probe, | |
215 | }; | |
216 | ||
217 | static int __init init(void) | |
218 | { | |
219 | return register_virtio_driver(&virtio_console); | |
220 | } | |
221 | module_init(init); | |
222 | ||
223 | MODULE_DEVICE_TABLE(virtio, id_table); | |
224 | MODULE_DESCRIPTION("Virtio console driver"); | |
225 | MODULE_LICENSE("GPL"); |