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GraphicsV 14

GraphicsV
» GraphicsV 14

Graphics Vector (42)

Entry  
R0 Bits 0-15: Offset within device
Bits 16-23: IIC base address
Bits 24-31: Reserved
R1 Pointer to buffer
R2 Byte count
R4 Bits 0-15: 14 (reason code)
Bits 16-23: Head number
Bits 24-31: Driver number
Exit  
R0 Return code
R1 Advanced by how many bytes read/written
R2 Number of bytes not transferred
R4 0
- All other registers preserved

Use

This call is used to perform IIC operations on the IIC busses managed by the driver.
Typically this will be DDC or EDID data from the attached monitor, for example the IIC base address for reading EDID data is 0xA1.

Notes

Due to its behaviour, it is not possible for a user of GraphicsV to make use of the EDID segment pointer by performing a write to bus address &60. Instead, it is the drivers responsibility to (where possible) automatically write to the segment pointer when asked to access an EDID address >= 256.

To protect against accidental corruption of EDID, it’s recommended that drivers do not allow EDID writes (i.e. operations to bus address &A0).

See also

  • GraphicsV
Revised on July 25, 2014 13:53:52 by Jeffrey Lee (213) (195.72.173.131)
Edit | Back in time (5 revisions) | See changes | History | Views: Print | Source | Linked from: HAL_VideoIICOp, HAL Video API, GraphicsV, Proposed GraphicsV enhancements

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