diff options
Diffstat (limited to 'chardev/char-hub.c')
| -rw-r--r-- | chardev/char-hub.c | 301 |
1 files changed, 301 insertions, 0 deletions
diff --git a/chardev/char-hub.c b/chardev/char-hub.c new file mode 100644 index 0000000..16ffee2 --- /dev/null +++ b/chardev/char-hub.c @@ -0,0 +1,301 @@ +/* + * QEMU Character Hub Device + * + * Author: Roman Penyaev <r.peniaev@gmail.com> + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN + * THE SOFTWARE. + */ + +#include "qemu/osdep.h" +#include "qapi/error.h" +#include "qemu/option.h" +#include "chardev/char.h" +#include "chardev-internal.h" + +/* + * Character hub device aggregates input from multiple backend devices + * and forwards it to a single frontend device. Additionally, hub + * device takes the output from the frontend device and sends it back + * to all the connected backend devices. + */ + +/* + * Write to all backends. Different backend devices accept data with + * various rate, so it is quite possible that one device returns less, + * then others. In this case we return minimum to the caller, + * expecting caller will repeat operation soon. When repeat happens + * send to the devices which consume data faster must be avoided + * for obvious reasons not to send data, which was already sent. + * Called with chr_write_lock held. + */ +static int hub_chr_write(Chardev *chr, const uint8_t *buf, int len) +{ + HubChardev *d = HUB_CHARDEV(chr); + int r, i, ret = len; + unsigned int written; + + /* Invalidate index on every write */ + d->be_eagain_ind = -1; + + for (i = 0; i < d->be_cnt; i++) { + if (!d->backends[i].be.chr->be_open) { + /* Skip closed backend */ + continue; + } + written = d->be_written[i] - d->be_min_written; + if (written) { + /* Written in the previous call so take into account */ + ret = MIN(written, ret); + continue; + } + r = qemu_chr_fe_write(&d->backends[i].be, buf, len); + if (r < 0) { + if (errno == EAGAIN) { + /* Set index and expect to be called soon on watch wake up */ + d->be_eagain_ind = i; + } + return r; + } + d->be_written[i] += r; + ret = MIN(r, ret); + } + d->be_min_written += ret; + + + return ret; +} + +static int hub_chr_can_read(void *opaque) +{ + HubCharBackend *backend = opaque; + CharBackend *fe = backend->hub->parent.be; + + if (fe && fe->chr_can_read) { + return fe->chr_can_read(fe->opaque); + } + + return 0; +} + +static void hub_chr_read(void *opaque, const uint8_t *buf, int size) +{ + HubCharBackend *backend = opaque; + CharBackend *fe = backend->hub->parent.be; + + if (fe && fe->chr_read) { + fe->chr_read(fe->opaque, buf, size); + } +} + +static void hub_chr_event(void *opaque, QEMUChrEvent event) +{ + HubCharBackend *backend = opaque; + HubChardev *d = backend->hub; + CharBackend *fe = d->parent.be; + + if (event == CHR_EVENT_OPENED) { + /* + * Catch up with what was already written while this backend + * was closed + */ + d->be_written[backend->be_ind] = d->be_min_written; + + if (d->be_event_opened_cnt++) { + /* Ignore subsequent open events from other backends */ + return; + } + } else if (event == CHR_EVENT_CLOSED) { + if (!d->be_event_opened_cnt) { + /* Don't go below zero. Probably assert is better */ + return; + } + if (--d->be_event_opened_cnt) { + /* Serve only the last one close event */ + return; + } + } + + if (fe && fe->chr_event) { + fe->chr_event(fe->opaque, event); + } +} + +static GSource *hub_chr_add_watch(Chardev *s, GIOCondition cond) +{ + HubChardev *d = HUB_CHARDEV(s); + Chardev *chr; + ChardevClass *cc; + + if (d->be_eagain_ind == -1) { + return NULL; + } + + assert(d->be_eagain_ind < d->be_cnt); + chr = qemu_chr_fe_get_driver(&d->backends[d->be_eagain_ind].be); + cc = CHARDEV_GET_CLASS(chr); + if (!cc->chr_add_watch) { + return NULL; + } + + return cc->chr_add_watch(chr, cond); +} + +static bool hub_chr_attach_chardev(HubChardev *d, Chardev *chr, + Error **errp) +{ + bool ret; + + if (d->be_cnt >= MAX_HUB) { + error_setg(errp, "hub: too many uses of chardevs '%s'" + " (maximum is " stringify(MAX_HUB) ")", + d->parent.label); + return false; + } + ret = qemu_chr_fe_init(&d->backends[d->be_cnt].be, chr, errp); + if (ret) { + d->backends[d->be_cnt].hub = d; + d->backends[d->be_cnt].be_ind = d->be_cnt; + d->be_cnt += 1; + } + + return ret; +} + +static void char_hub_finalize(Object *obj) +{ + HubChardev *d = HUB_CHARDEV(obj); + int i; + + for (i = 0; i < d->be_cnt; i++) { + qemu_chr_fe_deinit(&d->backends[i].be, false); + } +} + +static void hub_chr_update_read_handlers(Chardev *chr) +{ + HubChardev *d = HUB_CHARDEV(chr); + int i; + + for (i = 0; i < d->be_cnt; i++) { + qemu_chr_fe_set_handlers_full(&d->backends[i].be, + hub_chr_can_read, + hub_chr_read, + hub_chr_event, + NULL, + &d->backends[i], + chr->gcontext, true, false); + } +} + +static void qemu_chr_open_hub(Chardev *chr, + ChardevBackend *backend, + bool *be_opened, + Error **errp) +{ + ChardevHub *hub = backend->u.hub.data; + HubChardev *d = HUB_CHARDEV(chr); + strList *list = hub->chardevs; + + d->be_eagain_ind = -1; + + if (list == NULL) { + error_setg(errp, "hub: 'chardevs' list is not defined"); + return; + } + + while (list) { + Chardev *s; + + s = qemu_chr_find(list->value); + if (s == NULL) { + error_setg(errp, "hub: chardev can't be found by id '%s'", + list->value); + return; + } + if (CHARDEV_IS_HUB(s) || CHARDEV_IS_MUX(s)) { + error_setg(errp, "hub: multiplexers and hub devices can't be " + "stacked, check chardev '%s', chardev should not " + "be a hub device or have 'mux=on' enabled", + list->value); + return; + } + if (!hub_chr_attach_chardev(d, s, errp)) { + return; + } + list = list->next; + } + + /* Closed until an explicit event from backend */ + *be_opened = false; +} + +static void qemu_chr_parse_hub(QemuOpts *opts, ChardevBackend *backend, + Error **errp) +{ + ChardevHub *hub; + strList **tail; + int i; + + backend->type = CHARDEV_BACKEND_KIND_HUB; + hub = backend->u.hub.data = g_new0(ChardevHub, 1); + qemu_chr_parse_common(opts, qapi_ChardevHub_base(hub)); + + tail = &hub->chardevs; + + for (i = 0; i < MAX_HUB; i++) { + char optbuf[16]; + const char *dev; + + snprintf(optbuf, sizeof(optbuf), "chardevs.%u", i); + dev = qemu_opt_get(opts, optbuf); + if (!dev) { + break; + } + + QAPI_LIST_APPEND(tail, g_strdup(dev)); + } +} + +static void char_hub_class_init(ObjectClass *oc, const void *data) +{ + ChardevClass *cc = CHARDEV_CLASS(oc); + + cc->parse = qemu_chr_parse_hub; + cc->open = qemu_chr_open_hub; + cc->chr_write = hub_chr_write; + cc->chr_add_watch = hub_chr_add_watch; + /* We handle events from backends only */ + cc->chr_be_event = NULL; + cc->chr_update_read_handler = hub_chr_update_read_handlers; +} + +static const TypeInfo char_hub_type_info = { + .name = TYPE_CHARDEV_HUB, + .parent = TYPE_CHARDEV, + .class_init = char_hub_class_init, + .instance_size = sizeof(HubChardev), + .instance_finalize = char_hub_finalize, +}; + +static void register_types(void) +{ + type_register_static(&char_hub_type_info); +} + +type_init(register_types); |