This is a preliminary proposal for an extension to the v4l2 api.
To be discussed at the V4L2 'brainstorming' meeting in Warsaw, March 2011
Purpose: Provide basic controls for HDMI and DVI devices.
sink : HDMI/DVI/VGA receiver
source: HDMI/DVI/VGA transmitter
New Controls:
=============
These controls rely on control events to be able to notify the
application of any change.
The idea is to create an event that will be triggered by the control
framework whenever a control changes value.
TX source:
----------
Control: V4L2_CID_DV_TX_HOTPLUG
type: bitmask (output), read only
name: Hotplug
Hotplug is present on each output.
The hotplug is issued by the sink to indicate that an
edid exists and should be read by the source.
Not applicable for VGA connectors.
Control: V4L2_CID_DV_TX_RXSENSE
type: bitmask (output), read only
name: Rx Sense
Rx sense is present on each output.
Rx Sense is detection of pull-ups on the TMDS clock lines.
Normally means that the sink has left/entered standby.
Not applicable for VGA connectors.
Control: V4L2_CID_DV_TX_EDID_SEGMENT0_PRESENT
type: bitmask (output), read only
name: Edid segment 0
The source driver has read edid segment 0 from the sink.
Control: V4L2_CID_DV_TX_DVI_HDMI_MODE
type: menu, read and write
name: Hdmi/Dvi mode
Settings:
"HDMI"
"DVI-D"
RX sink:
--------
Control: V4L2_CID_DV_RX_5V
type: bitmask (input), read only
name: Rx 5V
The source must supply the sink with a +5v via the HDMI/DVI cable.
This is often used to power an eeprom which contains edid information,
such that the source can read the edid even if the sink
is in standby/power off.
Control: V4L2_CID_DV_CABLE_DETECT
type: bitmask (input), read only
name: Cable detect
This is not a part of the HDMI/DVI standards.
But many sinks (read monitors) uses a + 5v pull-up on a
ground pin (typically pin 15 on dvi) to detect if a cable is
is connected and terminated at the source end.
Control: V4L2_CID_DV_FORMAT_STATUS
type: menu, read only
name: Format status
Format status for the current selected input.
Statuses:
"No signal"
"Unknown"
"Unsupported"
"Encrypted"
"Valid/supported"
The input signal has changed format or status.
In the case of a valid signal use the
vidioc_query_dv_preset to read the new format.
Alternatively this could also be implemented as a bitmask with bits
for: 'signal present', 'encrypted', 'supported format'.
Or as three separate boolean controls.
New Events:
===========
V4L2_EVENT_TX_EDID
struct v4l2_event_tx_edid {
__u32 output;
__u32 present;
__u32 segment;
}
The source driver has read an edid segment from the sink.
One segment is 256 bytes and will contain one or two 128
bytes blocks. Most HDMI and DVI sinks will have only segment 0.
The driver should read segment 0 when hotplug is detected and
report this to userspace. The application can then use the
V4L2_G_EDID ioctl to get the actual edid data.
If the EDID data indicates the presence of further extension blocks the
userspace application can use the V4L2_REQ_EDID ioctl to trigger a read.
When the driver has read that extended segment it will generate a
V4L2_EVENT_TX_EDID event.
New Ioctls:
===========
TX source:
----------
V4L2_REQ_EDID
struct v4l2_req_edid {
__u32 output;
__u32 segment;
}
Trigger a read of a 256 bytes segment. Normally the driver will
read segment 0 by itself when hotplug is detected, But this ioctl
may also be used to trigger a re-read of segment 0.
V4L2_G_EDID
struct v4l2_g_edid {
__u32 output;
__u32 segment;
__u8 edid[256];
}
Get the edid segment indicated in the V4L2_EVENT_TX_EDID
RX sink:
--------
V4L2_S_EDID
struct v4l2_s_edid {
__u32 input;
__u32 segment;
__u8 _edid[256];
}
Set the edid information in the source.
Additional Controls and Status:
===============================
Controls and statuses we want to add.
Currently based on HDMI version 1.3a, must be updated
From Info frames
* Y0, Y1 RGB or YCBCR indicator.
* A0 Active Information Present. Indicates whether field
R0...R3 is valid. See
CEA-861-D table 8 for details.
* B0, B1 Bar Info data valid. See CEA-861-D table 8 for details.
HDMI Licensing, LLC Page 113 of 156
High-Definition Multimedia Interface
Specification Version 1.3a
* S0, S1 Scan Information (i.e. overscan, underscan). See
CEA-861-D table 8 for
details.
* C0, C1 Colorimetry (ITU BT.601, BT.709 etc.). See CEA-861-D
table 9 for
details.
* EC0, EC1, EC2 Extended Colorimetry (IEC 61966-2-4 etc.). See
CEA-861-D table 11 for
details.
* Q1, Q0 Quantization range (Full vs. Limited, etc.). See
CEA-861-D table 11 for
details.
* ITC IT Content. See CEA-861-D table 11 for details.
* M0, M1 Picture Aspect Ratio (4:3, 16:9). See CEA-861-D
table 9 for details.
* R0...R3 Active Format Aspect Ratio. See CEA-861-D table 10
and Annex H for
details.
* VIC0...VIC6 Video Format Identification Code. When transmitting
any video format in
section 6.2.4, above, an HDMI Source shall set
the VIC field to the Video
Code for that format. See CEA-861-D section 6.4
for details.
* PR0...PR3 Pixel Repetition factor. See CEA-861-D table 13 for
details.
* SC1, SC0 Non-uniform Picture Scaling. See CEA-861-D table 11.
A lot of these handle colorspace information. It is not clear yet
whether this
should be set up using S_FMT/mediabus APIs, or by explicit controls.
Martin Bugge
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