diff options
Diffstat (limited to 'Documentation/media/uapi/cec/cec-ioc-receive.rst')
| -rw-r--r-- | Documentation/media/uapi/cec/cec-ioc-receive.rst | 55 |
1 files changed, 53 insertions, 2 deletions
diff --git a/Documentation/media/uapi/cec/cec-ioc-receive.rst b/Documentation/media/uapi/cec/cec-ioc-receive.rst index dc2adb391c0a..267044f7ac30 100644 --- a/Documentation/media/uapi/cec/cec-ioc-receive.rst +++ b/Documentation/media/uapi/cec/cec-ioc-receive.rst @@ -51,13 +51,13 @@ A received message can be: be non-zero). To send a CEC message the application has to fill in the struct -:c:type:` cec_msg` and pass it to :ref:`ioctl CEC_TRANSMIT <CEC_TRANSMIT>`. +:c:type:`cec_msg` and pass it to :ref:`ioctl CEC_TRANSMIT <CEC_TRANSMIT>`. The :ref:`ioctl CEC_TRANSMIT <CEC_TRANSMIT>` is only available if ``CEC_CAP_TRANSMIT`` is set. If there is no more room in the transmit queue, then it will return -1 and set errno to the ``EBUSY`` error code. The transmit queue has enough room for 18 messages (about 1 second worth of 2-byte messages). Note that the CEC kernel framework will also reply -to core messages (see :ref:cec-core-processing), so it is not a good +to core messages (see :ref:`cec-core-processing`), so it is not a good idea to fully fill up the transmit queue. If the file descriptor is in non-blocking mode then the transmit will @@ -69,6 +69,18 @@ The ``sequence`` field is filled in for every transmit and this can be checked against the received messages to find the corresponding transmit result. +Normally calling :ref:`ioctl CEC_TRANSMIT <CEC_TRANSMIT>` when the physical +address is invalid (due to e.g. a disconnect) will return ``ENONET``. + +However, the CEC specification allows sending messages from 'Unregistered' to +'TV' when the physical address is invalid since some TVs pull the hotplug detect +pin of the HDMI connector low when they go into standby, or when switching to +another input. + +When the hotplug detect pin goes low the EDID disappears, and thus the +physical address, but the cable is still connected and CEC still works. +In order to detect/wake up the device it is allowed to send poll and 'Image/Text +View On' messages from initiator 0xf ('Unregistered') to destination 0 ('TV'). .. tabularcolumns:: |p{1.0cm}|p{3.5cm}|p{13.0cm}| @@ -289,3 +301,42 @@ Return Value On success 0 is returned, on error -1 and the ``errno`` variable is set appropriately. The generic error codes are described at the :ref:`Generic Error Codes <gen-errors>` chapter. + +The :ref:`ioctl CEC_RECEIVE <CEC_RECEIVE>` can return the following +error codes: + +EAGAIN + No messages are in the receive queue, and the filehandle is in non-blocking mode. + +ETIMEDOUT + The ``timeout`` was reached while waiting for a message. + +ERESTARTSYS + The wait for a message was interrupted (e.g. by Ctrl-C). + +The :ref:`ioctl CEC_TRANSMIT <CEC_TRANSMIT>` can return the following +error codes: + +ENOTTY + The ``CEC_CAP_TRANSMIT`` capability wasn't set, so this ioctl is not supported. + +EPERM + The CEC adapter is not configured, i.e. :ref:`ioctl CEC_ADAP_S_LOG_ADDRS <CEC_ADAP_S_LOG_ADDRS>` + has never been called. + +ENONET + The CEC adapter is not configured, i.e. :ref:`ioctl CEC_ADAP_S_LOG_ADDRS <CEC_ADAP_S_LOG_ADDRS>` + was called, but the physical address is invalid so no logical address was claimed. + An exception is made in this case for transmits from initiator 0xf ('Unregistered') + to destination 0 ('TV'). In that case the transmit will proceed as usual. + +EBUSY + Another filehandle is in exclusive follower or initiator mode, or the filehandle + is in mode ``CEC_MODE_NO_INITIATOR``. This is also returned if the transmit + queue is full. + +EINVAL + The contents of struct :c:type:`cec_msg` is invalid. + +ERESTARTSYS + The wait for a successful transmit was interrupted (e.g. by Ctrl-C). |