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Mailbox property interface
- The response overwrites the request.
- The callee is not allowed to return a different buffer address, this allows the caller to make independent asynchronous requests.
- The buffer itself is 16-byte aligned as only the upper 28 bits of the address can be passed via the mailbox.
- All u64/u32/u16 values are in host CPU endian order.
- Unknown tags are ignored (the response bit will not be set).
- Response may include unsolicited tags.
- Response tag lengths may be longer than expected if additional information is provided in a future format.
- The response is truncated to the provided buffer length.
- Incompatible changes require a new tag so that where the buffer is the size required by a previous version the truncated part should be readable as per the previous version.
- Response length indicates the desired length even when it is longer than the buffer size filled.
- Tag value length can be used to infer the version of the request/response.
- Tags should be processed in order except where an interface requires multiple tags for a single operation (like the frame buffer).
Mailbox messages:
- The mailbox interface has 28 bits (MSB) available for the value and 4 bits (LSB) for the channel.
- Request message: 28 bits (MSB) buffer address
- Response message: 28 bits (MSB) buffer address
- Channels 8 and 9 are used.
- Channel 8: Request from ARM for response by VC
- Channel 9: Request from VC for response by ARM (none currently defined)
Buffer contents:
- u32: buffer size in bytes (including the header values, the end tag and padding)
- u32: buffer request/response code
- Request codes:
- 0x00000000: process request
- All other values reserved
- Response codes:
- 0x80000000: request successful
- 0x80000001: error parsing request buffer (partial response)
- All other values reserved
- Request codes:
- u8...: sequence of concatenated tags
- u32: 0x0 (end tag)
- u8...: padding
Tag format:
- u32: tag identifier
- u32: value buffer size in bytes
- u32:
- Request codes:
- b31 clear: request
- b30-b0: reserved
- Response codes:
- b31 set: response
- b30-b0: value length in bytes
- Request codes:
- u8...: value buffer
- u8...: padding to align the tag to 32 bits.
- Tag: 0x00000001
- Request:
- Length: 0
- Response:
- Length: 4
- Value:
- u32: firmware revision
- Tag: 0x00010001
- Request:
- Length: 0
- Response:
- Length: 4
- Value:
- u32: board model
- Tag: 0x00010002
- Request:
- Length: 0
- Response:
- Length: 4
- Value:
- u32: board revision
- Tag: 0x00010003
- Request:
- Length: 0
- Response:
- Length: 6
- Value:
- u8...: MAC address in network byte order
- Tag: 0x00010004
- Request:
- Length: 0
- Response:
- Length: 8
- Value:
- u64: board serial
- Tag: 0x00010005
- Request:
- Length: 0
- Response:
- Length: 8
- Value:
- u32: base address in bytes
- u32: size in bytes
Future formats may specify multiple base+size combinations.
- Tag: 0x00010006
- Request:
- Length: 0
- Response:
- Length: 8
- Value:
- u32: base address in bytes
- u32: size in bytes
Future formats may specify multiple base+size combinations.
- Tag: 0x00010007
- Request:
- Length: 0
- Response:
- Length: variable (multiple of 8)
- Value:
- u32: parent clock id (0 for a root clock)
- u32: clock id
- (repeated)
Returns all clocks that exist in top down breadth first order. Clocks that depend on another clock should be defined as children of that clock. Clocks that depend on no other clocks should have no parent. Clock IDs are as in the clock section below.
(swarren: This clock message is much less well defined than the other clock message below. To be useful, you'd need to either return a clock name along with each clock so the caller knew what they all were, or pre-define the list of valid clock IDs as the other clock message does below)
(lp0: I've now made it clear that the clock IDs are as below, which is why I reserved 0)
- Tag: 0x00050001
- Request:
- Length: 0
- Response:
- Length: variable
- Value:
- u8...: ASCII command line string
Caller should not assume the string is null terminated.
- Tag: 0x00060001
- Request:
- Length: 0
- Response:
- Length: 4
- Value:
- u32: mask
- Mask:
- Bits 0-15: DMA channels 0-15 (0=do not use, 1=usable)
- Bits 16-31: reserved for future use
Caller assumes that the VC has enabled all the usable DMA channels.
Unique device IDs:
- 0x00000000: SD Card
- 0x00000001: UART0
- 0x00000002: UART1
- 0x00000003: USB HCD
- 0x00000004: I2C0
- 0x00000005: I2C1
- 0x00000006: I2C2
- 0x00000007: SPI
- 0x00000008: CCP2TX
- 0x00000009: Unknown (RPi4)
- 0x0000000a: Unknown (RPi4)
- Tag: 0x00020001
- Request:
- Length: 4
- Value:
- u32: device id
- Response:
- Length: 8
- Value:
- u32: device id
- u32: state
- State:
- Bit 0: 0=off, 1=on
- Bit 1: 0=device exists, 1=device does not exist
- Bits 2-31: reserved for future use
Response indicates current state.
- Tag: 0x00020002
- Request:
- Length: 4
- Value:
- u32: device id
- Response:
- Length: 8
- Value:
- u32: device id
- u32: enable wait time in microseconds
Response indicates wait time required after turning a device on before power is stable. Returns 0 wait time if the device does not exist.
- Tag: 0x00028001
- Request:
- Length: 8
- Value:
- u32: device id
- u32: state
- State:
- Bit 0: 0=off, 1=on
- Bit 1: 0=do not wait, 1=wait
- Bits 2-31: reserved for future use (set to 0)
- Response:
- Length: 8
- Value:
- u32: device id
- u32: state
- State:
- Bit 0: 0=off, 1=on
- Bit 1: 0=device exists, 1=device does not exist
- Bits 2-31: reserved for future use
Response indicates new state, with/without waiting for the power to become stable.
Unique clock IDs:
- 0x000000000: reserved
- 0x000000001: EMMC
- 0x000000002: UART
- 0x000000003: ARM
- 0x000000004: CORE
- 0x000000005: V3D
- 0x000000006: H264
- 0x000000007: ISP
- 0x000000008: SDRAM
- 0x000000009: PIXEL
- 0x00000000a: PWM
- 0x00000000b: HEVC
- 0x00000000c: EMMC2
- 0x00000000d: M2MC
- 0x00000000e: PIXEL_BVB
(swarren: I imagine there are more clocks than that; the clock message earlier returned clock parent information, and I doubt any of the clocks listed here are parents of each-other. At the very least I'd expect one more defined clock ID to represent the root crystal/PLL, and I'd expect there are a actually a variety of intermediate clocks between this and these peripherals).
All clocks are the base clocks for those peripherals, e.g. 3MHz for UART, 50/100MHz for EMMC, not the dividers applied using the peripheral.
- Tag: 0x00030001
- Request:
- Length: 4
- Value:
- u32: clock id
- Response:
- Length: 8
- Value:
- u32: clock id
- u32: state
- State:
- Bit 0: 0=off, 1=on
- Bit 1: 0=clock exists, 1=clock does not exist
- Bits 2-31: reserved for future use
- Tag: 0x00038001
- Request:
- Length: 8
- Value:
- u32: clock id
- u32: state
- State:
- Bit 0: 0=off, 1=on
- Bit 1: 0=clock exists, 1=clock does not exist
- Bits 2-31: reserved for future use (set to 0)
- Response:
- Length: 8
- Value:
- u32: clock id
- u32: state
- State:
- Bit 0: 0=off, 1=on
- Bit 1: 0=clock exists, 1=clock does not exist
- Bits 2-31: reserved for future use
(swarren: it doesn't seem to make sense for the request to have a "clock exists" bit, only the response)
(lp0: the lack of a response makes it unclear if the tag itself was unsupported)
- Tag: 0x00030002
- Request:
- Length: 4
- Value:
- u32: clock id
- Response:
- Length: 8
- Value:
- u32: clock id
- u32: rate (in Hz)
Next enable rate should be returned even if the clock is not running. A rate of 0 is returned if the clock does not exist.
- Tag: 0x00030041
- Request:
- Length: 0
- Response:
- Length: 8
- Value:
- u32: pin number
- u32: status
- Pin:
- 42: status led
- 130: power led
Response is the LED pin number and its status (0 or 1).
- Tag: 0x00034041
- Request:
- Length: 0
- Response:
- Length: 8
- Value:
- u32: pin number
- u32: status
- Pin:
- 42: status led
- 130: power led
Response is the LED pin number and its status (0 or 1).
- Tag: 0x00038041
- Request:
- Length: 8
- Value:
- u32: pin number
- u32: status
- Pin:
- 42: status led
- 130: power led
- Response:
- Length: 8
- Value:
- u32: pin number
- u32: status
- Pin:
- 42: status led
- 130: power led
Response is the LED pin number and the status to set (0 or 1) .
- Tag: 0x00030047
- Request:
- Length: 4
- Value:
- u32: clock id
- Response:
- Length: 8
- Value:
- u32: clock id
- u32: rate (in Hz)
Get the true/actual clock rate (instead of the last requested value returned by "Get clock rate"/0x0003002) which respects clamping, throttling and clock divider limitations.
- Tag: 0x00038002
- Request:
- Length: 12
- Value:
- u32: clock id
- u32: rate (in Hz)
- u32: skip setting turbo
- Response:
- Length: 8
- Value:
- u32: clock id
- u32: rate (in Hz)
Next supported enable rate should be returned even if the clock is not running. A rate of 0 is returned if the clock does not exist. The clock rate may be clamped to the supported range.
By default when setting arm freq above default, other turbo settings will be enabled (e.g. voltage, sdram and gpu frequencies). You can disable this effect by setting "skip setting turbo" to 1.
(swarren: As lp0 mentioned in the issue, min/max rates, and a list of valid parents would be useful response data from some message. Also, a set parent message might be useful if there are messages to get parenting information)
- Tag: 0x00030004
- Request:
- Length: 4
- Value:
- u32: clock id
- Response:
- Length: 8
- Value:
- u32: clock id
- u32: rate (in Hz)
Return the maximum supported clock rate for the given clock. Clocks should not be set higher than this.
- Tag: 0x00030007
- Request:
- Length: 4
- Value:
- u32: clock id
- Response:
- Length: 8
- Value:
- u32: clock id
- u32: rate (in Hz)
Return the minimum supported clock rate for the given clock. This may be used when idle.
- Tag: 0x00030009
- Request:
- Length: 4
- Value:
- u32: id
- Response:
- Length: 8
- Value:
- u32: id
- u32: level
Get the turbo state for index id. id should be 0. level will be zero for non-turbo and one for turbo.
- Tag: 0x00038009
- Request:
- Length: 8
- Value:
- u32: id
- u32: level
- Response:
- Length: 8
- Value:
- u32: id
- u32: level
Set the turbo state for index id. id should be zero. level will be zero for non-turbo and one for turbo. This will cause GPU clocks to be set to maximum when enabled and minimum when disabled.
Unique voltage IDs:
- 0x000000000: reserved
- 0x000000001: Core
- 0x000000002: SDRAM_C
- 0x000000003: SDRAM_P
- 0x000000004: SDRAM_I
- Tag: 0x00030003
- Request:
- Length: 4
- Value:
- u32: voltage id
- Response:
- Length: 8
- Value:
- u32: voltage id
- u32: value (absolute voltage in microvolts)
The voltage value may be clamped to the supported range. A value of 0x80000000 means the id was not valid.
- Tag: 0x00038003
- Request:
- Length: 8
- Value:
- u32: voltage id
- u32: value (specified as follows:
- value <= 16: relative to platform-specific typical voltage, in 25mV steps
- 16 < value < 500000: relative to platform-specific typical voltage, in microvolts
- value >= 500000: absolute voltage in microvolts
- Response:
- Length: 8
- Value:
- u32: voltage id
- u32: value (absolute voltage in microvolts)
The voltage value may be clamped to the supported range. A value of 0x80000000 means the id was not valid.
- Tag: 0x00030005
- Request:
- Length: 4
- Value:
- u32: voltage id
- Response:
- Length: 8
- Value:
- u32: voltage id
- u32: value (absolute voltage in microvolts)
Return the maximum supported voltage rate for the given id. Voltages should not be set higher than this.
- Tag: 0x00030008
- Request:
- Length: 4
- Value:
- u32: voltage id
- Response:
- Length: 8
- Value:
- u32: voltage id
- u32: value (absolute voltage in microvolts)
Return the minimum supported voltage rate for the given id. This may be used when idle.
- Tag: 0x00030006
- Request:
- Length: 4
- Value:
- u32: temperature id
- Response:
- Length: 8
- Value:
- u32: temperature id
- u32: value
Return the temperature of the SoC in thousandths of a degree C. id should be zero.
- Tag: 0x0003000a
- Request:
- Length: 4
- Value:
- u32: temperature id
- Response:
- Length: 8
- Value:
- u32: temperature id
- u32: value
Return the maximum safe temperature of the SoC in thousandths of a degree C. id should be zero. Overclock may be disabled above this temperature.
- Tag: 0x0003000c
- Request:
- Length: 12
- Value:
- u32: size
- u32: alignment
- u32: flags
- Response:
- Length: 4
- Value:
- u32: handle
Allocates contiguous memory on the GPU. size and alignment are in bytes. flags contain:
MEM_FLAG_DISCARDABLE = 1 << 0, /* can be resized to 0 at any time. Use for cached data */
MEM_FLAG_NORMAL = 0 << 2, /* normal allocating alias. Don't use from ARM */
MEM_FLAG_DIRECT = 1 << 2, /* 0xC alias uncached */
MEM_FLAG_COHERENT = 2 << 2, /* 0x8 alias. Non-allocating in L2 but coherent */
MEM_FLAG_L1_NONALLOCATING = (MEM_FLAG_DIRECT | MEM_FLAG_COHERENT), /* Allocating in L2 */
MEM_FLAG_ZERO = 1 << 4, /* initialise buffer to all zeros */
MEM_FLAG_NO_INIT = 1 << 5, /* don't initialise (default is initialise to all ones */
MEM_FLAG_HINT_PERMALOCK = 1 << 6, /* Likely to be locked for long periods of time. */
handle != 0 is success.
- Tag: 0x0003000d
- Request:
- Length: 4
- Value:
- u32: handle
- Response:
- Length: 4
- Value:
- u32: bus address
Lock buffer in place, and return a bus address. Must be done before memory can be accessed. bus address != 0 is success.
- Tag: 0x0003000e
- Request:
- Length: 4
- Value:
- u32: handle
- Response:
- Length: 4
- Value:
- u32: status
Unlock buffer. It retains contents, but may move. Needs to be locked before next use. status=0 is success.
- Tag: 0x0003000f
- Request:
- Length: 4
- Value:
- u32: handle
- Response:
- Length: 4
- Value:
- u32: status
Free the memory buffer. status=0 is success.
- Tag: 0x00030010
- Request:
- Length: 28
- Value:
- u32: function pointer
- u32: r0
- u32: r1
- u32: r2
- u32: r3
- u32: r4
- u32: r5
- Response:
- Length: 4
- Value:
- u32: r0
Calls the function at given (bus) address and with arguments given. E.g. r0 = fn(r0, r1, r2, r3, r4, r5); It blocks until call completes. The (GPU) instruction cache is implicitly flushed. Setting the lsb of function pointer address will suppress the instruction cache flush if you know the buffer hasn't changed since last execution.
- Tag: 0x00030014
- Request:
- Length: 4
- Value:
- u32: dispmanx resource handle
- Response:
- Length: 8
- Value:
- u32: 0 is successful
- u32: mem handle for resource
Gets the mem_handle associated with a created dispmanx resource. This can be locked and the memory directly written from the arm to avoid having to copy the image data to GPU.
- Tag: 0x00030020
- Request:
- Length: 4
- Value:
- u32: block number
- Response:
- Length: 136
- Value:
- u32: block number
- u32: status
- 128 bytes: EDID block
This reads the specified EDID block from attached HDMI/DVI device. There will always be at least one block of 128 bytes, but there may be additional blocks. You should keep requesting blocks (starting from 0) until the status returned is non-zero.
- All tags in the request are processed in one operation.
- It is not valid to mix Test tags with Get/Set tags in the same operation and no tags will be returned.
- Get tags will be processed after all Set tags.
- If an allocate buffer tag is omitted when setting parameters, then no change occurs unless it can be accommodated without changing the buffer base or size.
- When an allocate buffer response is returned, the old buffer area (if the base or size has changed) is implicitly freed.
For example:
- The current values/defaults are loaded into a temporary struct
- The tags are used to overwrite some or all of the values
- Validation of Test/Set tags occurs
- The Set changes are applied and responses based on the requested Get/Test/Set tags are written to the buffer
Duplicating the same tag in one request/response is prohibited. The expected result is either an error or implementation specified undefined behaviour (such as only using the last instance of the tag).
- Tag: 0x00040001
- Request:
- Length: 4
- Value:
- u32: alignment in bytes
- Response:
- Length: 8
- Value:
- u32: frame buffer base address in bytes
- u32: frame buffer size in bytes
If the requested alignment is unsupported then the current base and size (which may be 0 if not allocated) is returned and no change occurs.
- Tag: 0x00048001
- Request:
- Length: 0
- Response:
- Length: 0
Releases and disables the frame buffer.
- Tag: 0x00040002
- Request:
- Length: 4
- Value:
- u32: state
- State:
- Bit 0: 0=off, 1=on
- Bits 1-31: reserved for future use (set to 0)
- Response:
- Length: 4
- Value:
- u32: state
- State:
- Bit 0: 0=off, 1=on
- Bits 1-31: reserved for future use
- Tag: 0x00040003
- Request:
- Length: 0
- Response:
- Length: 8
- Value:
- u32: width in pixels
- u32: height in pixels
- Tag: 0x00044003
- Request:
- Length: 8
- Value:
- u32: width in pixels
- u32: height in pixels
- Response:
- Length: 8
- Value:
- u32: width in pixels
- u32: height in pixels
Response is the same as the request (or modified), to indicate if this configuration is supported (in combination with all the other settings). Does not modify the current hardware or frame buffer state.
- Tag: 0x00048003
- Request:
- Length: 8
- Value:
- u32: width in pixels
- u32: height in pixels
- Response:
- Length: 8
- Value:
- u32: width in pixels
- u32: height in pixels
The response may not be the same as the request so it must be checked. May be the previous width/height or 0 for unsupported.
- Tag: 0x00040004
- Request:
- Length: 0
- Response:
- Length: 8
- Value:
- u32: width in pixels
- u32: height in pixels
- Tag: 0x00044004
- Request:
- Length: 8
- Value:
- u32: width in pixels
- u32: height in pixels
- Response:
- Length: 8
- Value:
- u32: width in pixels
- u32: height in pixels
Response is the same as the request (or modified), to indicate if this configuration is supported (in combination with all the other settings). Does not modify the current hardware or frame buffer state.
- Tag: 0x00048004
- Request:
- Length: 8
- Value:
- u32: width in pixels
- u32: height in pixels
- Response:
- Length: 8
- Value:
- u32: width in pixels
- u32: height in pixels
The response may not be the same as the request so it must be checked. May be the previous width/height or 0 for unsupported.
- Tag: 0x00040005
- Request:
- Length: 0
- Response:
- Length: 4
- Value:
- u32: bits per pixel
- Tag: 0x00044005
- Request:
- Length: 4
- Value:
- u32: bits per pixel
- Response:
- Length: 4
- Value:
- u32: bits per pixel
Response is the same as the request (or modified), to indicate if this configuration is supported (in combination with all the other settings). Does not modify the current hardware or frame buffer state.
- Tag: 0x00048005
- Request:
- Length: 4
- Value:
- u32: bits per pixel
- Response:
- Length: 4
- Value:
- u32: bits per pixel
The response may not be the same as the request so it must be checked. May be the previous depth or 0 for unsupported.
- Tag: 0x00040006
- Request:
- Length: 0
- Response:
- Length: 4
- Value:
- u32: state
- State:
- 0x0: BGR
- 0x1: RGB
- Tag: 0x00044006
- Request:
- Length: 4
- Value:
- u32: state (as above)
- Response:
- Length: 4
- Value:
- u32: state (as above)
Response is the same as the request (or modified), to indicate if this configuration is supported (in combination with all the other settings). Does not modify the current hardware or frame buffer state.
- Tag: 0x00048006
- Request:
- Length: 4
- Value:
- u32: state (as above)
- Response:
- Length: 4
- Value:
- u32: state (as above)
The response may not be the same as the request so it must be checked.
- Tag: 0x00040007
- Request:
- Length: 0
- Response:
- Length: 4
- Value:
- u32: state
- State: * 0x0: Alpha channel enabled (0 = fully opaque) * 0x1: Alpha channel reversed (0 = fully transparent) * 0x2: Alpha channel ignored
- Tag: 0x00044007
- Request:
- Length: 4
- Value:
- u32: state (as above)
- Response:
- Length: 4
- Value:
- u32: state (as above)
Response is the same as the request (or modified), to indicate if this configuration is supported (in combination with all the other settings). Does not modify the current hardware or frame buffer state.
- Tag: 0x00048007
- Request:
- Length: 4
- Value:
- u32: state (as above)
- Response:
- Length: 4
- Value:
- u32: state (as above)
The response may not be the same as the request so it must be checked.
- Tag: 0x00040008
- Request:
- Length: 0
- Response:
- Length: 4
- Value:
- u32: bytes per line
- Tag: 0x00040009
- Request:
- Length: 0
- Response:
- Length: 8
- Value:
- u32: X in pixels
- u32: Y in pixels
- Tag: 0x00044009
- Request:
- Length: 8
- Value:
- u32: X in pixels
- u32: Y in pixels
- Response:
- Length: 8
- Value:
- u32: X in pixels
- u32: Y in pixels
Response is the same as the request (or modified), to indicate if this configuration is supported (in combination with all the other settings). Does not modify the current hardware or frame buffer state.
- Tag: 0x00048009
- Request:
- Length: 8
- Value:
- u32: X in pixels
- u32: Y in pixels
- Response:
- Length: 8
- Value:
- u32: X in pixels
- u32: Y in pixels
The response may not be the same as the request so it must be checked. May be the previous offset or 0 for unsupported.
- Tag: 0x0004000a
- Request:
- Length: 0
- Response:
- Length: 16
- Value:
- u32: top in pixels
- u32: bottom in pixels
- u32: left in pixels
- u32: right in pixels
- Tag: 0x0004400a
- Request:
- Length: 16
- Value:
- u32: top in pixels
- u32: bottom in pixels
- u32: left in pixels
- u32: right in pixels
- Response:
- Length: 16
- Value:
- u32: top in pixels
- u32: bottom in pixels
- u32: left in pixels
- u32: right in pixels
Response is the same as the request (or modified), to indicate if this configuration is supported (in combination with all the other settings). Does not modify the current hardware or frame buffer state.
- Tag: 0x0004800a
- Request:
- Length: 16
- Value:
- u32: top in pixels
- u32: bottom in pixels
- u32: left in pixels
- u32: right in pixels
- Response:
- Length: 16
- Value:
- u32: top in pixels
- u32: bottom in pixels
- u32: left in pixels
- u32: right in pixels
The response may not be the same as the request so it must be checked. May be the previous overscan or 0 for unsupported.
- Tag: 0x0004000b
- Request:
- Length: 0
- Response:
- Length: 1024
- Value:
- u32...: RGBA palette values (index 0 to 255)
- Tag: 0x0004400b
- Request:
- Length: 24..1032
- Value:
- u32: offset: first palette index to set (0-255)
- u32: length: number of palette entries to set (1-256)
- u32...: RGBA palette values (offset to offset+length-1)
- Response:
- Length: 4
- Value:
- u32: 0=valid, 1=invalid
Response is the same as the request (or modified), to indicate if this configuration is supported (in combination with all the other settings). Does not modify the current hardware or frame buffer state.
- Tag: 0x0004800b
- Request:
- Length: 24..1032
- Value:
- u32: offset: first palette index to set (0-255)
- u32: length: number of palette entries to set (1-256)
- u32...: RGBA palette values (offset to offset+length-1)
- Response:
- Length: 4
- Value:
- u32: 0=valid, 1=invalid
The response may not be the same as the request so it must be checked. Palette changes should not be partially applied.
- Tag: 0x00008010
- Request:
- Length: 24
- Value:
- u32: width
- u32: height
- u32: (unused)
- u32: pointer to pixels
- u32: hotspotX
- u32: hotspotY
- Response:
- Length: 4
- Value:
- u32: 0=valid, 1=invalid
Format is 32bpp (ARGB). Width and height should be >= 16 and (width * height) <= 64.
- Tag: 0x00008011
- Request:
- Length: 16
- Value:
- u32: enable (1=visible, 0=invisible)
- u32: x
- u32: y
- u32: flags
- Response:
- Length: 4
- Value:
- u32: 0=valid, 1=invalid
The flags control: bit0: clean=display coords, set=framebuffer coords
if Set Cursor Info hasn't been called a default cursor will be used (64x64 with hotspot at 0,0).
(swarren: I agree that a single message for each of framebuffer get/test/set might be better - that way, the complete configuration is always available for test or set to operate on, although for test, the individual test messages might be useful alongside the overall configuration test message. What about multi-head; can both HDMI and TV out be active at once, or is there only 1 head? Are options like HDMI YUV vs. RGB, HDMI audio, HDMI EDID retrieval, HDMI reduced CE vs. PC RGB space, ... supported?)
(lp0: having a single message does not imply that the complete configuration is always available - the caller may be using an older version that lacks additional information, and all these extra options would be more easily supported as separate values than adding to a single large struct)
- Tag: 0x00008012
- Request:
- Length: 8
- Value:
- u32: display number
- u32: address of 768 byte gamma table: 256 bytes red, 256 bytes green, 256 blue.
- Response:
- Length: 0
The tag was added on 2019-01-09. As the Pi4 uses a different gamma mechanism, this tag currently doesn't work on the Pi4. The developer has written a small example program.