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Diffstat (limited to 'Documentation/media/uapi/cec')
| -rw-r--r-- | Documentation/media/uapi/cec/cec-ioc-receive.rst | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/Documentation/media/uapi/cec/cec-ioc-receive.rst b/Documentation/media/uapi/cec/cec-ioc-receive.rst index 3ce7307..267044f 100644 --- a/Documentation/media/uapi/cec/cec-ioc-receive.rst +++ b/Documentation/media/uapi/cec/cec-ioc-receive.rst @@ -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}| @@ -315,6 +327,8 @@ EPERM 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 |
