| Entry | |
|---|---|
| R0 | Head number (0-based) |
| R4 | Bits 0-23: 15 (reason code) |
| Bits 24-31: Display number |
| Exit | |
|---|---|
| R0 | 0 or error block pointer |
| R4 | 0 |
| - | All other registers preserved |
This call is used to switch the display output from one graphics card head to another.
If the call is left unclaimed, the kernel has no HAL-based fallback in place.