media: cec: improve cec status documentation
Clarify the description of status bits, particularly w.r.t. ERROR and NACK. Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Hans Verkuil <hansverk@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
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@ -246,7 +246,10 @@ CEC_TX_STATUS_LOW_DRIVE:
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CEC_TX_STATUS_ERROR:
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some unspecified error occurred: this can be one of ARB_LOST
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or LOW_DRIVE if the hardware cannot differentiate or something
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else entirely.
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else entirely. Some hardware only supports OK and FAIL as the
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result of a transmit, i.e. there is no way to differentiate
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between the different possible errors. In that case map FAIL
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to CEC_TX_STATUS_NACK and not to CEC_TX_STATUS_ERROR.
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CEC_TX_STATUS_MAX_RETRIES:
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could not transmit the message after trying multiple times.
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@ -231,26 +231,32 @@ View On' messages from initiator 0xf ('Unregistered') to destination 0 ('TV').
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- ``CEC_TX_STATUS_OK``
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- 0x01
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- The message was transmitted successfully. This is mutually
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exclusive with :ref:`CEC_TX_STATUS_MAX_RETRIES <CEC-TX-STATUS-MAX-RETRIES>`. Other bits can still
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be set if earlier attempts met with failure before the transmit
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was eventually successful.
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exclusive with :ref:`CEC_TX_STATUS_MAX_RETRIES <CEC-TX-STATUS-MAX-RETRIES>`.
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Other bits can still be set if earlier attempts met with failure before
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the transmit was eventually successful.
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* .. _`CEC-TX-STATUS-ARB-LOST`:
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- ``CEC_TX_STATUS_ARB_LOST``
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- 0x02
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- CEC line arbitration was lost.
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- CEC line arbitration was lost, i.e. another transmit started at the
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same time with a higher priority. Optional status, not all hardware
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can detect this error condition.
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* .. _`CEC-TX-STATUS-NACK`:
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- ``CEC_TX_STATUS_NACK``
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- 0x04
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- Message was not acknowledged.
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- Message was not acknowledged. Note that some hardware cannot tell apart
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a 'Not Acknowledged' status from other error conditions, i.e. the result
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of a transmit is just OK or FAIL. In that case this status will be
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returned when the transmit failed.
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* .. _`CEC-TX-STATUS-LOW-DRIVE`:
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- ``CEC_TX_STATUS_LOW_DRIVE``
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- 0x08
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- Low drive was detected on the CEC bus. This indicates that a
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follower detected an error on the bus and requests a
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retransmission.
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retransmission. Optional status, not all hardware can detect this
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error condition.
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* .. _`CEC-TX-STATUS-ERROR`:
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- ``CEC_TX_STATUS_ERROR``
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@ -258,14 +264,14 @@ View On' messages from initiator 0xf ('Unregistered') to destination 0 ('TV').
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- Some error occurred. This is used for any errors that do not fit
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``CEC_TX_STATUS_ARB_LOST`` or ``CEC_TX_STATUS_LOW_DRIVE``, either because
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the hardware could not tell which error occurred, or because the hardware
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tested for other conditions besides those two.
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tested for other conditions besides those two. Optional status.
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* .. _`CEC-TX-STATUS-MAX-RETRIES`:
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- ``CEC_TX_STATUS_MAX_RETRIES``
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- 0x20
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- The transmit failed after one or more retries. This status bit is
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mutually exclusive with :ref:`CEC_TX_STATUS_OK <CEC-TX-STATUS-OK>`. Other bits can still
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be set to explain which failures were seen.
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mutually exclusive with :ref:`CEC_TX_STATUS_OK <CEC-TX-STATUS-OK>`.
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Other bits can still be set to explain which failures were seen.
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.. tabularcolumns:: |p{5.6cm}|p{0.9cm}|p{11.0cm}|
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