1 /*
2 * QEMU Character Hub Device
3 *
4 * Author: Roman Penyaev <r.peniaev@gmail.com>
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a copy
7 * of this software and associated documentation files (the "Software"), to deal
8 * in the Software without restriction, including without limitation the rights
9 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
10 * copies of the Software, and to permit persons to whom the Software is
11 * furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
21 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
22 * THE SOFTWARE.
23 */
24
25 #include "qemu/osdep.h"
26 #include "qapi/error.h"
27 #include "qemu/option.h"
28 #include "chardev/char.h"
29 #include "chardev-internal.h"
30
31 /*
32 * Character hub device aggregates input from multiple backend devices
33 * and forwards it to a single frontend device. Additionally, hub
34 * device takes the output from the frontend device and sends it back
35 * to all the connected backend devices.
36 */
37
38 /*
39 * Write to all backends. Different backend devices accept data with
40 * various rate, so it is quite possible that one device returns less,
41 * then others. In this case we return minimum to the caller,
42 * expecting caller will repeat operation soon. When repeat happens
43 * send to the devices which consume data faster must be avoided
44 * for obvious reasons not to send data, which was already sent.
45 * Called with chr_write_lock held.
46 */
hub_chr_write(Chardev * chr,const uint8_t * buf,int len)47 static int hub_chr_write(Chardev *chr, const uint8_t *buf, int len)
48 {
49 HubChardev *d = HUB_CHARDEV(chr);
50 int r, i, ret = len;
51 unsigned int written;
52
53 /* Invalidate index on every write */
54 d->be_eagain_ind = -1;
55
56 for (i = 0; i < d->be_cnt; i++) {
57 if (!d->backends[i].be.chr->be_open) {
58 /* Skip closed backend */
59 continue;
60 }
61 written = d->be_written[i] - d->be_min_written;
62 if (written) {
63 /* Written in the previous call so take into account */
64 ret = MIN(written, ret);
65 continue;
66 }
67 r = qemu_chr_fe_write(&d->backends[i].be, buf, len);
68 if (r < 0) {
69 if (errno == EAGAIN) {
70 /* Set index and expect to be called soon on watch wake up */
71 d->be_eagain_ind = i;
72 }
73 return r;
74 }
75 d->be_written[i] += r;
76 ret = MIN(r, ret);
77 }
78 d->be_min_written += ret;
79
80
81 return ret;
82 }
83
hub_chr_can_read(void * opaque)84 static int hub_chr_can_read(void *opaque)
85 {
86 HubCharBackend *backend = opaque;
87 CharBackend *fe = backend->hub->parent.be;
88
89 if (fe && fe->chr_can_read) {
90 return fe->chr_can_read(fe->opaque);
91 }
92
93 return 0;
94 }
95
hub_chr_read(void * opaque,const uint8_t * buf,int size)96 static void hub_chr_read(void *opaque, const uint8_t *buf, int size)
97 {
98 HubCharBackend *backend = opaque;
99 CharBackend *fe = backend->hub->parent.be;
100
101 if (fe && fe->chr_read) {
102 fe->chr_read(fe->opaque, buf, size);
103 }
104 }
105
hub_chr_event(void * opaque,QEMUChrEvent event)106 static void hub_chr_event(void *opaque, QEMUChrEvent event)
107 {
108 HubCharBackend *backend = opaque;
109 HubChardev *d = backend->hub;
110 CharBackend *fe = d->parent.be;
111
112 if (event == CHR_EVENT_OPENED) {
113 /*
114 * Catch up with what was already written while this backend
115 * was closed
116 */
117 d->be_written[backend->be_ind] = d->be_min_written;
118
119 if (d->be_event_opened_cnt++) {
120 /* Ignore subsequent open events from other backends */
121 return;
122 }
123 } else if (event == CHR_EVENT_CLOSED) {
124 if (!d->be_event_opened_cnt) {
125 /* Don't go below zero. Probably assert is better */
126 return;
127 }
128 if (--d->be_event_opened_cnt) {
129 /* Serve only the last one close event */
130 return;
131 }
132 }
133
134 if (fe && fe->chr_event) {
135 fe->chr_event(fe->opaque, event);
136 }
137 }
138
hub_chr_add_watch(Chardev * s,GIOCondition cond)139 static GSource *hub_chr_add_watch(Chardev *s, GIOCondition cond)
140 {
141 HubChardev *d = HUB_CHARDEV(s);
142 Chardev *chr;
143 ChardevClass *cc;
144
145 if (d->be_eagain_ind == -1) {
146 return NULL;
147 }
148
149 assert(d->be_eagain_ind < d->be_cnt);
150 chr = qemu_chr_fe_get_driver(&d->backends[d->be_eagain_ind].be);
151 cc = CHARDEV_GET_CLASS(chr);
152 if (!cc->chr_add_watch) {
153 return NULL;
154 }
155
156 return cc->chr_add_watch(chr, cond);
157 }
158
hub_chr_attach_chardev(HubChardev * d,Chardev * chr,Error ** errp)159 static bool hub_chr_attach_chardev(HubChardev *d, Chardev *chr,
160 Error **errp)
161 {
162 bool ret;
163
164 if (d->be_cnt >= MAX_HUB) {
165 error_setg(errp, "hub: too many uses of chardevs '%s'"
166 " (maximum is " stringify(MAX_HUB) ")",
167 d->parent.label);
168 return false;
169 }
170 ret = qemu_chr_fe_init(&d->backends[d->be_cnt].be, chr, errp);
171 if (ret) {
172 d->backends[d->be_cnt].hub = d;
173 d->backends[d->be_cnt].be_ind = d->be_cnt;
174 d->be_cnt += 1;
175 }
176
177 return ret;
178 }
179
char_hub_finalize(Object * obj)180 static void char_hub_finalize(Object *obj)
181 {
182 HubChardev *d = HUB_CHARDEV(obj);
183 int i;
184
185 for (i = 0; i < d->be_cnt; i++) {
186 qemu_chr_fe_deinit(&d->backends[i].be, false);
187 }
188 }
189
hub_chr_update_read_handlers(Chardev * chr)190 static void hub_chr_update_read_handlers(Chardev *chr)
191 {
192 HubChardev *d = HUB_CHARDEV(chr);
193 int i;
194
195 for (i = 0; i < d->be_cnt; i++) {
196 qemu_chr_fe_set_handlers_full(&d->backends[i].be,
197 hub_chr_can_read,
198 hub_chr_read,
199 hub_chr_event,
200 NULL,
201 &d->backends[i],
202 chr->gcontext, true, false);
203 }
204 }
205
qemu_chr_open_hub(Chardev * chr,ChardevBackend * backend,bool * be_opened,Error ** errp)206 static void qemu_chr_open_hub(Chardev *chr,
207 ChardevBackend *backend,
208 bool *be_opened,
209 Error **errp)
210 {
211 ChardevHub *hub = backend->u.hub.data;
212 HubChardev *d = HUB_CHARDEV(chr);
213 strList *list = hub->chardevs;
214
215 d->be_eagain_ind = -1;
216
217 if (list == NULL) {
218 error_setg(errp, "hub: 'chardevs' list is not defined");
219 return;
220 }
221
222 while (list) {
223 Chardev *s;
224
225 s = qemu_chr_find(list->value);
226 if (s == NULL) {
227 error_setg(errp, "hub: chardev can't be found by id '%s'",
228 list->value);
229 return;
230 }
231 if (CHARDEV_IS_HUB(s) || CHARDEV_IS_MUX(s)) {
232 error_setg(errp, "hub: multiplexers and hub devices can't be "
233 "stacked, check chardev '%s', chardev should not "
234 "be a hub device or have 'mux=on' enabled",
235 list->value);
236 return;
237 }
238 if (!hub_chr_attach_chardev(d, s, errp)) {
239 return;
240 }
241 list = list->next;
242 }
243
244 /* Closed until an explicit event from backend */
245 *be_opened = false;
246 }
247
qemu_chr_parse_hub(QemuOpts * opts,ChardevBackend * backend,Error ** errp)248 static void qemu_chr_parse_hub(QemuOpts *opts, ChardevBackend *backend,
249 Error **errp)
250 {
251 ChardevHub *hub;
252 strList **tail;
253 int i;
254
255 backend->type = CHARDEV_BACKEND_KIND_HUB;
256 hub = backend->u.hub.data = g_new0(ChardevHub, 1);
257 qemu_chr_parse_common(opts, qapi_ChardevHub_base(hub));
258
259 tail = &hub->chardevs;
260
261 for (i = 0; i < MAX_HUB; i++) {
262 char optbuf[16];
263 const char *dev;
264
265 snprintf(optbuf, sizeof(optbuf), "chardevs.%u", i);
266 dev = qemu_opt_get(opts, optbuf);
267 if (!dev) {
268 break;
269 }
270
271 QAPI_LIST_APPEND(tail, g_strdup(dev));
272 }
273 }
274
char_hub_class_init(ObjectClass * oc,const void * data)275 static void char_hub_class_init(ObjectClass *oc, const void *data)
276 {
277 ChardevClass *cc = CHARDEV_CLASS(oc);
278
279 cc->parse = qemu_chr_parse_hub;
280 cc->open = qemu_chr_open_hub;
281 cc->chr_write = hub_chr_write;
282 cc->chr_add_watch = hub_chr_add_watch;
283 /* We handle events from backends only */
284 cc->chr_be_event = NULL;
285 cc->chr_update_read_handler = hub_chr_update_read_handlers;
286 }
287
288 static const TypeInfo char_hub_type_info = {
289 .name = TYPE_CHARDEV_HUB,
290 .parent = TYPE_CHARDEV,
291 .class_init = char_hub_class_init,
292 .instance_size = sizeof(HubChardev),
293 .instance_finalize = char_hub_finalize,
294 };
295
register_types(void)296 static void register_types(void)
297 {
298 type_register_static(&char_hub_type_info);
299 }
300
301 type_init(register_types);
302