1 .. -*- coding: utf-8; mode: rst -*-
7 ********************************
8 ioctls CEC_G_MODE and CEC_S_MODE
9 ********************************
11 CEC_G_MODE, CEC_S_MODE - Get or set exclusive use of the CEC adapter
16 .. c:function:: int ioctl( int fd, CEC_G_MODE, __u32 *argp )
19 .. c:function:: int ioctl( int fd, CEC_S_MODE, __u32 *argp )
26 File descriptor returned by :c:func:`open() <cec-open>`.
34 By default any filehandle can use :ref:`CEC_TRANSMIT`, but in order to prevent
35 applications from stepping on each others toes it must be possible to
36 obtain exclusive access to the CEC adapter. This ioctl sets the
37 filehandle to initiator and/or follower mode which can be exclusive
38 depending on the chosen mode. The initiator is the filehandle that is
39 used to initiate messages, i.e. it commands other CEC devices. The
40 follower is the filehandle that receives messages sent to the CEC
41 adapter and processes them. The same filehandle can be both initiator
42 and follower, or this role can be taken by two different filehandles.
44 When a CEC message is received, then the CEC framework will decide how
45 it will be processed. If the message is a reply to an earlier
46 transmitted message, then the reply is sent back to the filehandle that
47 is waiting for it. In addition the CEC framework will process it.
49 If the message is not a reply, then the CEC framework will process it
50 first. If there is no follower, then the message is just discarded and a
51 feature abort is sent back to the initiator if the framework couldn't
52 process it. If there is a follower, then the message is passed on to the
53 follower who will use :ref:`ioctl CEC_RECEIVE <CEC_RECEIVE>` to dequeue
54 the new message. The framework expects the follower to make the right
57 The CEC framework will process core messages unless requested otherwise
58 by the follower. The follower can enable the passthrough mode. In that
59 case, the CEC framework will pass on most core messages without
60 processing them and the follower will have to implement those messages.
61 There are some messages that the core will always process, regardless of
62 the passthrough mode. See :ref:`cec-core-processing` for details.
64 If there is no initiator, then any CEC filehandle can use
65 :ref:`ioctl CEC_TRANSMIT <CEC_TRANSMIT>`. If there is an exclusive
66 initiator then only that initiator can call
67 :ref:`CEC_TRANSMIT`. The follower can of course
68 always call :ref:`ioctl CEC_TRANSMIT <CEC_TRANSMIT>`.
70 Available initiator modes are:
72 .. tabularcolumns:: |p{5.6cm}|p{0.9cm}|p{11.0cm}|
74 .. _cec-mode-initiator_e:
76 .. flat-table:: Initiator Modes
81 * .. _`CEC-MODE-NO-INITIATOR`:
83 - ``CEC_MODE_NO_INITIATOR``
85 - This is not an initiator, i.e. it cannot transmit CEC messages or
86 make any other changes to the CEC adapter.
87 * .. _`CEC-MODE-INITIATOR`:
89 - ``CEC_MODE_INITIATOR``
91 - This is an initiator (the default when the device is opened) and
92 it can transmit CEC messages and make changes to the CEC adapter,
93 unless there is an exclusive initiator.
94 * .. _`CEC-MODE-EXCL-INITIATOR`:
96 - ``CEC_MODE_EXCL_INITIATOR``
98 - This is an exclusive initiator and this file descriptor is the
99 only one that can transmit CEC messages and make changes to the
100 CEC adapter. If someone else is already the exclusive initiator
101 then an attempt to become one will return the ``EBUSY`` error code
105 Available follower modes are:
107 .. tabularcolumns:: |p{6.6cm}|p{0.9cm}|p{10.0cm}|
109 .. _cec-mode-follower_e:
111 .. flat-table:: Follower Modes
116 * .. _`CEC-MODE-NO-FOLLOWER`:
118 - ``CEC_MODE_NO_FOLLOWER``
120 - This is not a follower (the default when the device is opened).
121 * .. _`CEC-MODE-FOLLOWER`:
123 - ``CEC_MODE_FOLLOWER``
125 - This is a follower and it will receive CEC messages unless there
126 is an exclusive follower. You cannot become a follower if
127 :ref:`CEC_CAP_TRANSMIT <CEC-CAP-TRANSMIT>` is not set or if :ref:`CEC_MODE_NO_INITIATOR <CEC-MODE-NO-INITIATOR>`
128 was specified, the ``EINVAL`` error code is returned in that case.
129 * .. _`CEC-MODE-EXCL-FOLLOWER`:
131 - ``CEC_MODE_EXCL_FOLLOWER``
133 - This is an exclusive follower and only this file descriptor will
134 receive CEC messages for processing. If someone else is already
135 the exclusive follower then an attempt to become one will return
136 the ``EBUSY`` error code. You cannot become a follower if
137 :ref:`CEC_CAP_TRANSMIT <CEC-CAP-TRANSMIT>` is not set or if :ref:`CEC_MODE_NO_INITIATOR <CEC-MODE-NO-INITIATOR>`
138 was specified, the ``EINVAL`` error code is returned in that case.
139 * .. _`CEC-MODE-EXCL-FOLLOWER-PASSTHRU`:
141 - ``CEC_MODE_EXCL_FOLLOWER_PASSTHRU``
143 - This is an exclusive follower and only this file descriptor will
144 receive CEC messages for processing. In addition it will put the
145 CEC device into passthrough mode, allowing the exclusive follower
146 to handle most core messages instead of relying on the CEC
147 framework for that. If someone else is already the exclusive
148 follower then an attempt to become one will return the ``EBUSY`` error
149 code. You cannot become a follower if :ref:`CEC_CAP_TRANSMIT <CEC-CAP-TRANSMIT>`
150 is not set or if :ref:`CEC_MODE_NO_INITIATOR <CEC-MODE-NO-INITIATOR>` was specified,
151 the ``EINVAL`` error code is returned in that case.
152 * .. _`CEC-MODE-MONITOR-PIN`:
154 - ``CEC_MODE_MONITOR_PIN``
156 - Put the file descriptor into pin monitoring mode. Can only be used in
157 combination with :ref:`CEC_MODE_NO_INITIATOR <CEC-MODE-NO-INITIATOR>`,
158 otherwise the ``EINVAL`` error code will be returned.
159 This mode requires that the :ref:`CEC_CAP_MONITOR_PIN <CEC-CAP-MONITOR-PIN>`
160 capability is set, otherwise the ``EINVAL`` error code is returned.
161 While in pin monitoring mode this file descriptor can receive the
162 ``CEC_EVENT_PIN_LOW`` and ``CEC_EVENT_PIN_HIGH`` events to see the
163 low-level CEC pin transitions. This is very useful for debugging.
164 This mode is only allowed if the process has the ``CAP_NET_ADMIN``
165 capability. If that is not set, then the ``EPERM`` error code is returned.
166 * .. _`CEC-MODE-MONITOR`:
168 - ``CEC_MODE_MONITOR``
170 - Put the file descriptor into monitor mode. Can only be used in
171 combination with :ref:`CEC_MODE_NO_INITIATOR <CEC-MODE-NO-INITIATOR>`,i
172 otherwise the ``EINVAL`` error code will be returned.
173 In monitor mode all messages this CEC
174 device transmits and all messages it receives (both broadcast
175 messages and directed messages for one its logical addresses) will
176 be reported. This is very useful for debugging. This is only
177 allowed if the process has the ``CAP_NET_ADMIN`` capability. If
178 that is not set, then the ``EPERM`` error code is returned.
179 * .. _`CEC-MODE-MONITOR-ALL`:
181 - ``CEC_MODE_MONITOR_ALL``
183 - Put the file descriptor into 'monitor all' mode. Can only be used
184 in combination with :ref:`CEC_MODE_NO_INITIATOR <CEC-MODE-NO-INITIATOR>`, otherwise
185 the ``EINVAL`` error code will be returned. In 'monitor all' mode all messages
186 this CEC device transmits and all messages it receives, including
187 directed messages for other CEC devices will be reported. This is
188 very useful for debugging, but not all devices support this. This
189 mode requires that the :ref:`CEC_CAP_MONITOR_ALL <CEC-CAP-MONITOR-ALL>` capability is set,
190 otherwise the ``EINVAL`` error code is returned. This is only allowed if
191 the process has the ``CAP_NET_ADMIN`` capability. If that is not
192 set, then the ``EPERM`` error code is returned.
195 Core message processing details:
197 .. tabularcolumns:: |p{6.6cm}|p{10.9cm}|
199 .. _cec-core-processing:
201 .. flat-table:: Core Message Processing
206 * .. _`CEC-MSG-GET-CEC-VERSION`:
208 - ``CEC_MSG_GET_CEC_VERSION``
209 - When in passthrough mode this message has to be handled by
210 userspace, otherwise the core will return the CEC version that was
211 set with :ref:`ioctl CEC_ADAP_S_LOG_ADDRS <CEC_ADAP_S_LOG_ADDRS>`.
212 * .. _`CEC-MSG-GIVE-DEVICE-VENDOR-ID`:
214 - ``CEC_MSG_GIVE_DEVICE_VENDOR_ID``
215 - When in passthrough mode this message has to be handled by
216 userspace, otherwise the core will return the vendor ID that was
217 set with :ref:`ioctl CEC_ADAP_S_LOG_ADDRS <CEC_ADAP_S_LOG_ADDRS>`.
218 * .. _`CEC-MSG-ABORT`:
221 - When in passthrough mode this message has to be handled by
222 userspace, otherwise the core will return a feature refused
223 message as per the specification.
224 * .. _`CEC-MSG-GIVE-PHYSICAL-ADDR`:
226 - ``CEC_MSG_GIVE_PHYSICAL_ADDR``
227 - When in passthrough mode this message has to be handled by
228 userspace, otherwise the core will report the current physical
230 * .. _`CEC-MSG-GIVE-OSD-NAME`:
232 - ``CEC_MSG_GIVE_OSD_NAME``
233 - When in passthrough mode this message has to be handled by
234 userspace, otherwise the core will report the current OSD name as
235 was set with :ref:`ioctl CEC_ADAP_S_LOG_ADDRS <CEC_ADAP_S_LOG_ADDRS>`.
236 * .. _`CEC-MSG-GIVE-FEATURES`:
238 - ``CEC_MSG_GIVE_FEATURES``
239 - When in passthrough mode this message has to be handled by
240 userspace, otherwise the core will report the current features as
241 was set with :ref:`ioctl CEC_ADAP_S_LOG_ADDRS <CEC_ADAP_S_LOG_ADDRS>`
242 or the message is ignored if the CEC version was older than 2.0.
243 * .. _`CEC-MSG-USER-CONTROL-PRESSED`:
245 - ``CEC_MSG_USER_CONTROL_PRESSED``
246 - If :ref:`CEC_CAP_RC <CEC-CAP-RC>` is set, then generate a remote control key
247 press. This message is always passed on to userspace.
248 * .. _`CEC-MSG-USER-CONTROL-RELEASED`:
250 - ``CEC_MSG_USER_CONTROL_RELEASED``
251 - If :ref:`CEC_CAP_RC <CEC-CAP-RC>` is set, then generate a remote control key
252 release. This message is always passed on to userspace.
253 * .. _`CEC-MSG-REPORT-PHYSICAL-ADDR`:
255 - ``CEC_MSG_REPORT_PHYSICAL_ADDR``
256 - The CEC framework will make note of the reported physical address
257 and then just pass the message on to userspace.
264 On success 0 is returned, on error -1 and the ``errno`` variable is set
265 appropriately. The generic error codes are described at the
266 :ref:`Generic Error Codes <gen-errors>` chapter.
268 The :ref:`ioctl CEC_S_MODE <CEC_S_MODE>` can return the following
272 The requested mode is invalid.
275 Monitor mode is requested without having root permissions
278 Someone else is already an exclusive follower or initiator.