HAL_VideoSetDAG (changes)

Showing changes from revision #3 to #4: Added | Removed | Changed

Hardware Abstraction Layer

HAL entry points from RISC OS

» HAL_Video_SetDAG HAL_VideoSetDAG

HAL_Video_SetDAG HAL_VideoSetDAG

(HAL entry #47)

  void HAL_Video_SetDAG(uint HAL_VideoSetDAG(uint DAG, uint paddr)

Use

This is an internal call for OS use only and should not be used by user software. User software should use GraphicsV instead of interacting with the HAL directly.

The OS has a video buffer which is >= total display size, and may be using bank switching (several display buffers) or hardware scroll within the total video buffer.

• DAG=1 will be start address of current total video buffer
• DAG=2 will be end address (exclusive) of current total video buffer
• DAG=0 will be start address in buffer for current display

HALs should respond differently depending on whether hardware scroll is supported or not. (The OS will already know this from HAL_Video_Features). HAL_VideoFeatures).

No hardware scroll

Only DAG=0 is significant, and the end address of the current display is implied by the size of the current mode. Calls with DAG=1,2 should be ignored.

Hardware scroll

DAG=0 again defines display start. DAG=2 defines the last address (exclusive) that should be displayed before wrapping back (if reached within display size), and DAG=1 defines the address to which accesses should wrap back.

See also

• HAL Video API

Information source: Kernel.Docs.HAL.HAL_API in CVS