diff options
Diffstat (limited to 'Documentation/media/kapi')
| -rw-r--r-- | Documentation/media/kapi/cec-core.rst | 38 | ||||
| -rw-r--r-- | Documentation/media/kapi/csi2.rst | 61 | ||||
| -rw-r--r-- | Documentation/media/kapi/dtv-core.rst | 8 |
3 files changed, 85 insertions, 22 deletions
diff --git a/Documentation/media/kapi/cec-core.rst b/Documentation/media/kapi/cec-core.rst index 88c33b53ec13..81c6d8e93774 100644 --- a/Documentation/media/kapi/cec-core.rst +++ b/Documentation/media/kapi/cec-core.rst @@ -37,9 +37,8 @@ The struct cec_adapter represents the CEC adapter hardware. It is created by calling cec_allocate_adapter() and deleted by calling cec_delete_adapter(): .. c:function:: - 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); + struct cec_adapter *cec_allocate_adapter(const struct cec_adap_ops *ops, void *priv, + const char *name, u32 caps, u8 available_las); .. c:function:: void cec_delete_adapter(struct cec_adapter *adap); @@ -66,20 +65,19 @@ 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: .. c:function:: - int cec_register_adapter(struct cec_adapter \*adap); + int cec_register_adapter(struct cec_adapter *adap, struct device *parent); + +where parent is the parent device. To unregister the devices call: .. c:function:: - void cec_unregister_adapter(struct cec_adapter \*adap); + 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 @@ -106,13 +104,13 @@ your driver: 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); + void (*adap_status)(struct cec_adapter *adap, struct seq_file *file); /* High-level callbacks */ ... }; -The three low-level ops deal with various aspects of controlling the CEC adapter +The five low-level ops deal with various aspects of controlling the CEC adapter hardware: @@ -238,6 +236,18 @@ When a CEC message was received: Speaks for itself. +Implementing the interrupt handler +---------------------------------- + +Typically the CEC hardware provides interrupts that signal when a transmit +finished and whether it was successful or not, and it provides and interrupt +when a CEC message was received. + +The CEC driver should always process the transmit interrupts first before +handling the receive interrupt. The framework expects to see the cec_transmit_done +call before the cec_received_msg call, otherwise it can get confused if the +received message was in reply to the transmitted message. + Implementing the High-Level CEC Adapter --------------------------------------- @@ -247,11 +257,11 @@ CEC protocol driven. The following high-level callbacks are available: .. code-block:: none struct cec_adap_ops { - /\* Low-level callbacks \*/ + /* Low-level callbacks */ ... - /\* High-level CEC message callback \*/ - int (\*received)(struct cec_adapter \*adap, struct cec_msg \*msg); + /* 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 @@ -263,7 +273,7 @@ received CEC message 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. +it will not do anything with it. CEC framework functions diff --git a/Documentation/media/kapi/csi2.rst b/Documentation/media/kapi/csi2.rst new file mode 100644 index 000000000000..2004db00b12b --- /dev/null +++ b/Documentation/media/kapi/csi2.rst @@ -0,0 +1,61 @@ +MIPI CSI-2 +========== + +CSI-2 is a data bus intended for transferring images from cameras to +the host SoC. It is defined by the `MIPI alliance`_. + +.. _`MIPI alliance`: http://www.mipi.org/ + +Transmitter drivers +------------------- + +CSI-2 transmitter, such as a sensor or a TV tuner, drivers need to +provide the CSI-2 receiver with information on the CSI-2 bus +configuration. These include the V4L2_CID_LINK_FREQ and +V4L2_CID_PIXEL_RATE controls and +(:c:type:`v4l2_subdev_video_ops`->s_stream() callback). These +interface elements must be present on the sub-device represents the +CSI-2 transmitter. + +The V4L2_CID_LINK_FREQ control is used to tell the receiver driver the +frequency (and not the symbol rate) of the link. The +V4L2_CID_PIXEL_RATE is may be used by the receiver to obtain the pixel +rate the transmitter uses. The +:c:type:`v4l2_subdev_video_ops`->s_stream() callback provides an +ability to start and stop the stream. + +The value of the V4L2_CID_PIXEL_RATE is calculated as follows:: + + pixel_rate = link_freq * 2 * nr_of_lanes / bits_per_sample + +where + +.. list-table:: variables in pixel rate calculation + :header-rows: 1 + + * - variable or constant + - description + * - link_freq + - The value of the V4L2_CID_LINK_FREQ integer64 menu item. + * - nr_of_lanes + - Number of data lanes used on the CSI-2 link. This can + be obtained from the OF endpoint configuration. + * - 2 + - Two bits are transferred per clock cycle per lane. + * - bits_per_sample + - Number of bits per sample. + +The transmitter drivers must configure the CSI-2 transmitter to *LP-11 +mode* whenever the transmitter is powered on but not active. Some +transmitters do this automatically but some have to be explicitly +programmed to do so. + +Receiver drivers +---------------- + +Before the receiver driver may enable the CSI-2 transmitter by using +the :c:type:`v4l2_subdev_video_ops`->s_stream(), it must have powered +the transmitter up by using the +:c:type:`v4l2_subdev_core_ops`->s_power() callback. This may take +place either indirectly by using :c:func:`v4l2_pipeline_pm_use` or +directly. diff --git a/Documentation/media/kapi/dtv-core.rst b/Documentation/media/kapi/dtv-core.rst index a3c4642eabfc..ff86bf0abeae 100644 --- a/Documentation/media/kapi/dtv-core.rst +++ b/Documentation/media/kapi/dtv-core.rst @@ -8,14 +8,6 @@ Digital TV Common functions .. kernel-doc:: drivers/media/dvb-core/dvbdev.h - - -.. kernel-doc:: drivers/media/dvb-core/dvb_math.h - :export: drivers/media/dvb-core/dvb_math.c - -.. kernel-doc:: drivers/media/dvb-core/dvbdev.h - :export: drivers/media/dvb-core/dvbdev.c - Digital TV Ring buffer ---------------------- |