xref: /openbmc/qemu/chardev/char-io.c (revision 33956e47)
1  /*
2   * QEMU System Emulator
3   *
4   * Copyright (c) 2003-2008 Fabrice Bellard
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  #include "qemu/osdep.h"
25  #include "chardev/char-io.h"
26  
27  typedef struct IOWatchPoll {
28      GSource parent;
29  
30      QIOChannel *ioc;
31      GSource *src;
32  
33      IOCanReadHandler *fd_can_read;
34      GSourceFunc fd_read;
35      void *opaque;
36      GMainContext *context;
37  } IOWatchPoll;
38  
39  static IOWatchPoll *io_watch_poll_from_source(GSource *source)
40  {
41      return container_of(source, IOWatchPoll, parent);
42  }
43  
44  static gboolean io_watch_poll_prepare(GSource *source,
45                                        gint *timeout)
46  {
47      IOWatchPoll *iwp = io_watch_poll_from_source(source);
48      bool now_active = iwp->fd_can_read(iwp->opaque) > 0;
49      bool was_active = iwp->src != NULL;
50      if (was_active == now_active) {
51          return FALSE;
52      }
53  
54      /*
55       * We do not register the QIOChannel watch as a child GSource.
56       * The 'prepare' function on the parent GSource will be
57       * skipped if a child GSource's 'prepare' function indicates
58       * readiness. We need this prepare function be guaranteed
59       * to run on *every* iteration of the main loop, because
60       * it is critical to ensure we remove the QIOChannel watch
61       * if 'fd_can_read' indicates the frontend cannot receive
62       * more data.
63       */
64      if (now_active) {
65          iwp->src = qio_channel_create_watch(
66              iwp->ioc, G_IO_IN | G_IO_ERR | G_IO_HUP | G_IO_NVAL);
67          g_source_set_callback(iwp->src, iwp->fd_read, iwp->opaque, NULL);
68          g_source_attach(iwp->src, iwp->context);
69      } else {
70          g_source_destroy(iwp->src);
71          g_source_unref(iwp->src);
72          iwp->src = NULL;
73      }
74      return FALSE;
75  }
76  
77  static gboolean io_watch_poll_check(GSource *source)
78  {
79      return FALSE;
80  }
81  
82  static gboolean io_watch_poll_dispatch(GSource *source, GSourceFunc callback,
83                                         gpointer user_data)
84  {
85      abort();
86  }
87  
88  static void io_watch_poll_finalize(GSource *source)
89  {
90      /*
91       * Due to a glib bug, removing the last reference to a source
92       * inside a finalize callback causes recursive locking (and a
93       * deadlock).  This is not a problem inside other callbacks,
94       * including dispatch callbacks, so we call io_remove_watch_poll
95       * to remove this source.  At this point, iwp->src must
96       * be NULL, or we would leak it.
97       */
98      IOWatchPoll *iwp = io_watch_poll_from_source(source);
99      assert(iwp->src == NULL);
100  }
101  
102  static GSourceFuncs io_watch_poll_funcs = {
103      .prepare = io_watch_poll_prepare,
104      .check = io_watch_poll_check,
105      .dispatch = io_watch_poll_dispatch,
106      .finalize = io_watch_poll_finalize,
107  };
108  
109  GSource *io_add_watch_poll(Chardev *chr,
110                          QIOChannel *ioc,
111                          IOCanReadHandler *fd_can_read,
112                          QIOChannelFunc fd_read,
113                          gpointer user_data,
114                          GMainContext *context)
115  {
116      IOWatchPoll *iwp;
117      char *name;
118  
119      iwp = (IOWatchPoll *) g_source_new(&io_watch_poll_funcs,
120                                         sizeof(IOWatchPoll));
121      iwp->fd_can_read = fd_can_read;
122      iwp->opaque = user_data;
123      iwp->ioc = ioc;
124      iwp->fd_read = (GSourceFunc) fd_read;
125      iwp->src = NULL;
126      iwp->context = context;
127  
128      name = g_strdup_printf("chardev-iowatch-%s", chr->label);
129      g_source_set_name((GSource *)iwp, name);
130      g_free(name);
131  
132      g_source_attach(&iwp->parent, context);
133      g_source_unref(&iwp->parent);
134      return (GSource *)iwp;
135  }
136  
137  static void io_remove_watch_poll(GSource *source)
138  {
139      IOWatchPoll *iwp;
140  
141      iwp = io_watch_poll_from_source(source);
142      if (iwp->src) {
143          g_source_destroy(iwp->src);
144          g_source_unref(iwp->src);
145          iwp->src = NULL;
146      }
147      g_source_destroy(&iwp->parent);
148  }
149  
150  void remove_fd_in_watch(Chardev *chr)
151  {
152      if (chr->gsource) {
153          io_remove_watch_poll(chr->gsource);
154          chr->gsource = NULL;
155      }
156  }
157  
158  int io_channel_send_full(QIOChannel *ioc,
159                           const void *buf, size_t len,
160                           int *fds, size_t nfds)
161  {
162      size_t offset = 0;
163  
164      while (offset < len) {
165          ssize_t ret = 0;
166          struct iovec iov = { .iov_base = (char *)buf + offset,
167                               .iov_len = len - offset };
168  
169          ret = qio_channel_writev_full(
170              ioc, &iov, 1,
171              fds, nfds, 0, NULL);
172          if (ret == QIO_CHANNEL_ERR_BLOCK) {
173              if (offset) {
174                  return offset;
175              }
176  
177              errno = EAGAIN;
178              return -1;
179          } else if (ret < 0) {
180              errno = EINVAL;
181              return -1;
182          }
183  
184          offset += ret;
185      }
186  
187      return offset;
188  }
189  
190  int io_channel_send(QIOChannel *ioc, const void *buf, size_t len)
191  {
192      return io_channel_send_full(ioc, buf, len, NULL, 0);
193  }
194