Entry | |
---|---|
R0 | Reason |
R1 | 223 (&DF) |
R2 | Display number |
R3 | Reason 0: Undefined |
Reason 1: Pointer to device descriptor |
# | Hex # | Action |
---|---|---|
0 | &00 | Device deregistered |
1 | &01 | Device registered |
This service call is issued by the kernel when video drivers register or deregister with the system.
Under RISC OS 5, the display number in R2 corresponds to the GraphicsV driver number. Reason 1 is issued when a driver calls OS_ScreenMode 65, just after the kernel marks the driver as being ready for use. However because GraphicsV does not use device descriptors, the descriptor pointed to by R3 will be empty (a single terminator word). Reason 0 is issued when a driver calls OS_ScreenMode 66, before the kernel marks the driver as having stopped.
Under RISC OS Select, the display number in R2 corresponds to the VideoV? driver number, and the service calls are issued at the appropriate times for the VideoV API.