On 06/16/2016 10:12 PM, Mauro Carvalho Chehab wrote: > Em Fri, 29 Apr 2016 15:52:22 +0200 > Hans Verkuil <hverkuil@xxxxxxxxx> escreveu: > >> From: Hans Verkuil <hansverk@xxxxxxxxx> >> >> Document the new HDMI CEC framework. > > As we'll be moving documentation to Sphinx/Rst, it would be good if > you could make it work fine with sphinx, as this will likely be needed > for Kernel 4.9. Right now it most works, although several warnings are > produced: Would it be a problem if this conversion is done later in a separate patch? I'm all for it, but I don't have the time at the moment to do this. 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unexpected unindent. > /devel/v4l/patchwork/tmp/cec.txt:224: WARNING: Inline emphasis start-string without end-string. > /devel/v4l/patchwork/tmp/cec.txt:224: WARNING: Inline emphasis start-string without end-string. > /devel/v4l/patchwork/tmp/cec.txt:224: WARNING: Inline emphasis start-string without end-string. > /devel/v4l/patchwork/tmp/cec.txt:238: WARNING: Inline emphasis start-string without end-string. > /devel/v4l/patchwork/tmp/cec.txt:238: WARNING: Inline emphasis start-string without end-string. > /devel/v4l/patchwork/tmp/cec.txt:243: WARNING: Inline emphasis start-string without end-string. > /devel/v4l/patchwork/tmp/cec.txt:258: WARNING: Inline emphasis start-string without end-string. > /devel/v4l/patchwork/tmp/cec.txt:258: WARNING: Inline emphasis start-string without end-string. > > >> >> Signed-off-by: Hans Verkuil <hansverk@xxxxxxxxx> >> [k.debski@xxxxxxxxxxx: add DocBook documentation by Hans Verkuil, with >> Signed-off-by: Kamil Debski <kamil@xxxxxxxxx> >> Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx> >> --- >> Documentation/cec.txt | 267 ++++++++++++++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 267 insertions(+) >> create mode 100644 Documentation/cec.txt >> >> diff --git a/Documentation/cec.txt b/Documentation/cec.txt >> new file mode 100644 >> index 0000000..75155fe >> --- /dev/null >> +++ b/Documentation/cec.txt >> @@ -0,0 +1,267 @@ >> +CEC Kernel Support >> +================== >> + >> +The CEC framework provides a unified kernel interface for use with HDMI CEC >> +hardware. It is designed to handle a multiple types of hardware (receivers, >> +transmitters, USB dongles). The framework also gives the option to decide >> +what to do in the kernel driver and what should be handled by userspace >> +applications. In addition it integrates the remote control passthrough >> +feature into the kernel's remote control framework. >> + >> + >> +The CEC Protocol >> +---------------- >> + >> +The CEC protocol enables consumer electronic devices to communicate with each >> +other through the HDMI connection. The protocol uses logical addresses in the >> +communication. The logical address is strictly connected with the functionality >> +provided by the device. The TV acting as the communication hub is always >> +assigned address 0. The physical address is determined by the physical >> +connection between devices. >> + >> +The CEC framework described here is up to date with the CEC 2.0 specification. >> +It is documented in the HDMI 1.4 specification with the new 2.0 bits documented >> +in the HDMI 2.0 specification. But for most of the features the freely available >> +HDMI 1.3a specification is sufficient: >> + >> +http://www.microprocessor.org/HDMISpecification13a.pdf >> + >> + >> +The Kernel Interface >> +==================== >> + >> +CEC Adapter >> +----------- >> + >> +The struct cec_adapter represents the CEC adapter hardware. It is created by >> +calling cec_allocate_adapter() and deleted by calling cec_delete_adapter(): >> + >> +struct cec_adapter *cec_allocate_adapter(const struct cec_adap_ops *ops, >> + void *priv, const char *name, u32 caps, u8 available_las, >> + struct device *parent); >> +void cec_delete_adapter(struct cec_adapter *adap); >> + >> +To create an adapter you need to pass the following information: >> + >> +ops: adapter operations which are called by the CEC framework and that you >> +have to implement. >> + >> +priv: will be stored in adap->priv and can be used by the adapter ops. >> + >> +name: the name of the CEC adapter. Note: this name will be copied. >> + >> +caps: capabilities of the CEC adapter. These capabilities determine the >> + capabilities of the hardware and which parts are to be handled >> + by userspace and which parts are handled by kernelspace. The >> + capabilities are returned by CEC_ADAP_G_CAPS. >> + >> +available_las: the number of simultaneous logical addresses that this >> + adapter can handle. Must be 1 <= available_las <= CEC_MAX_LOG_ADDRS. >> + >> +parent: the parent device. >> + >> + >> +To register the /dev/cecX device node and the remote control device (if >> +CEC_CAP_RC is set) you call: >> + >> +int cec_register_adapter(struct cec_adapter *adap); >> + >> +To unregister the devices call: >> + >> +void cec_unregister_adapter(struct cec_adapter *adap); >> + >> +Note: if cec_register_adapter() fails, then call cec_delete_adapter() to >> +clean up. But if cec_register_adapter() succeeded, then only call >> +cec_unregister_adapter() to clean up, never cec_delete_adapter(). The >> +unregister function will delete the adapter automatically once the last user >> +of that /dev/cecX device has closed its file handle. >> + >> + >> +Implementing the Low-Level CEC Adapter >> +-------------------------------------- >> + >> +The following low-level adapter operations have to be implemented in >> +your driver: >> + >> +struct cec_adap_ops { >> + /* Low-level callbacks */ >> + int (*adap_enable)(struct cec_adapter *adap, bool enable); >> + int (*adap_monitor_all_enable)(struct cec_adapter *adap, bool enable); >> + int (*adap_log_addr)(struct cec_adapter *adap, u8 logical_addr); >> + int (*adap_transmit)(struct cec_adapter *adap, u8 attempts, >> + u32 signal_free_time, struct cec_msg *msg); >> + void (*adap_log_status)(struct cec_adapter *adap); >> + >> + /* High-level callbacks */ >> + ... >> +}; >> + >> +The three low-level ops deal with various aspects of controlling the CEC adapter >> +hardware: >> + >> + >> +To enable/disable the hardware: >> + >> + int (*adap_enable)(struct cec_adapter *adap, bool enable); >> + >> +This callback enables or disables the CEC hardware. Enabling the CEC hardware >> +means powering it up in a state where no logical addresses are claimed. This >> +op assumes that the physical address (adap->phys_addr) is valid when enable is >> +true and will not change while the CEC adapter remains enabled. The initial >> +state of the CEC adapter after calling cec_allocate_adapter() is disabled. >> + >> +Note that adap_enable must return 0 if enable is false. >> + >> + >> +To enable/disable the 'monitor all' mode: >> + >> + int (*adap_monitor_all_enable)(struct cec_adapter *adap, bool enable); >> + >> +If enabled, then the adapter should be put in a mode to also monitor messages >> +that not for us. Not all hardware supports this and this function is only >> +called if the CEC_CAP_MONITOR_ALL capability is set. This callback is optional >> +(some hardware may always be in 'monitor all' mode). >> + >> +Note that adap_monitor_all_enable must return 0 if enable is false. >> + >> + >> +To program a new logical address: >> + >> + int (*adap_log_addr)(struct cec_adapter *adap, u8 logical_addr); >> + >> +If logical_addr == CEC_LOG_ADDR_INVALID then all programmed logical addresses >> +are to be erased. Otherwise the given logical address should be programmed. >> +If the maximum number of available logical addresses is exceeded, then it >> +should return -ENXIO. Once a logical address is programmed the CEC hardware >> +can receive directed messages to that address. >> + >> +Note that adap_log_addr must return 0 if logical_addr is CEC_LOG_ADDR_INVALID. >> + >> + >> +To transmit a new message: >> + >> + int (*adap_transmit)(struct cec_adapter *adap, u8 attempts, >> + u32 signal_free_time, struct cec_msg *msg); >> + >> +This transmits a new message. The attempts argument is the suggested number of >> +attempts for the transmit. >> + >> +The signal_free_time is the number of data bit periods that the adapter should >> +wait when the line is free before attempting to send a message. This value >> +depends on whether this transmit is a retry, a message from a new initiator or >> +a new message for the same initiator. Most hardware will handle this >> +automatically, but in some cases this information is needed. >> + >> +The CEC_FREE_TIME_TO_USEC macro can be used to convert signal_free_time to >> +microseconds (one data bit period is 2.4 ms). >> + >> + >> +To log the current CEC hardware status: >> + >> + void (*adap_status)(struct cec_adapter *adap, struct seq_file *file); >> + >> +This optional callback can be used to show the status of the CEC hardware. >> +The status is available through debugfs: cat /sys/kernel/debug/cec/cecX/status >> + >> + >> +Your adapter driver will also have to react to events (typically interrupt >> +driven) by calling into the framework in the following situations: >> + >> +When a transmit finished (successfully or otherwise): >> + >> +void cec_transmit_done(struct cec_adapter *adap, u8 status, u8 arb_lost_cnt, >> + u8 nack_cnt, u8 low_drive_cnt, u8 error_cnt); >> + >> +The status can be one of: >> + >> +CEC_TX_STATUS_OK: the transmit was successful. >> +CEC_TX_STATUS_ARB_LOST: arbitration was lost: another CEC initiator >> +took control of the CEC line and you lost the arbitration. >> +CEC_TX_STATUS_NACK: the message was nacked (for a directed message) or >> +acked (for a broadcast message). A retransmission is needed. >> +CEC_TX_STATUS_LOW_DRIVE: low drive was detected on the CEC bus. This >> +indicates that a follower detected an error on the bus and requested a >> +retransmission. >> +CEC_TX_STATUS_ERROR: some unspecified error occurred: this can be one of >> +the previous two if the hardware cannot differentiate or something else >> +entirely. >> +CEC_TX_STATUS_MAX_RETRIES: could not transmit the message after >> +trying multiple times. Should only be set by the driver if it has hardware >> +support for retrying messages. If set, then the framework assumes that it >> +doesn't have to make another attempt to transmit the message since the >> +hardware did that already. >> + >> +The *_cnt arguments are the number of error conditions that were seen. >> +This may be 0 if no information is available. Drivers that do not support >> +hardware retry can just set the counter corresponding to the transmit error >> +to 1, if the hardware does support retry then either set these counters to >> +0 if the hardware provides no feedback of which errors occurred and how many >> +times, or fill in the correct values as reported by the hardware. >> + >> +When a CEC message was received: >> + >> +void cec_received_msg(struct cec_adapter *adap, struct cec_msg *msg); >> + >> +Speaks for itself. >> + >> +Implementing the High-Level CEC Adapter >> +--------------------------------------- >> + >> +The low-level operations drive the hardware, the high-level operations are >> +CEC protocol driven. The following high-level callbacks are available: >> + >> +struct cec_adap_ops { >> + /* Low-level callbacks */ >> + ... >> + >> + /* High-level CEC message callback */ >> + int (*received)(struct cec_adapter *adap, struct cec_msg *msg); >> +}; >> + >> +The received() callback allows the driver to optionally handle a newly >> +received CEC message >> + >> + int (*received)(struct cec_adapter *adap, struct cec_msg *msg); >> + >> +If the driver wants to process a CEC message, then it can implement this >> +callback. If it doesn't want to handle this message, then it should return >> +-ENOMSG, otherwise the CEC framework assumes it processed this message and >> +it will not no anything with it. >> + >> + >> +CEC framework functions >> +----------------------- >> + >> +CEC Adapter drivers can call the following CEC framework functions: >> + >> +int cec_transmit_msg(struct cec_adapter *adap, struct cec_msg *msg, >> + bool block); >> + >> +Transmit a CEC message. If block is true, then wait until the message has been >> +transmitted, otherwise just queue it and return. >> + >> +void cec_s_phys_addr(struct cec_adapter *adap, u16 phys_addr, bool block); >> + >> +Change the physical address. This function will set adap->phys_addr and >> +send an event if it has changed. If cec_s_log_addrs() has been called and >> +the physical address has become valid, then the CEC framework will start >> +claiming the logical addresses. If block is true, then this function won't >> +return until this process has finished. >> + >> +When the physical address is set to a valid value the CEC adapter will >> +be enabled (see the adap_enable op). When it is set to CEC_PHYS_ADDR_INVALID, >> +then the CEC adapter will be disabled. If you change a valid physical address >> +to another valid physical address, then this function will first set the >> +address to CEC_PHYS_ADDR_INVALID before enabling the new physical address. >> + >> +int cec_s_log_addrs(struct cec_adapter *adap, >> + struct cec_log_addrs *log_addrs, bool block); >> + >> +Claim the CEC logical addresses. Should never be called if CEC_CAP_LOG_ADDRS >> +is set. If block is true, then wait until the logical addresses have been >> +claimed, otherwise just queue it and return. To unconfigure all logical >> +addresses call this function with log_addrs set to NULL or with >> +log_addrs->num_log_addrs set to 0. The block argument is ignored when >> +unconfiguring. This function will just return if the physical address is >> +invalid. Once the physical address becomes valid, then the framework will >> +attempt to claim these logical addresses. > > > > Thanks, > Mauro > -- > To unsubscribe from this list: send the line "unsubscribe linux-media" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
