Showing changes from revision #9 to #10:
Added | Removed | Changed
Entry | |
---|---|
R0 | Suggested mode number or Mode Selector Block |
R4 | Bits 0-15: 16 (reason code) |
Bits 16-23: Head number | |
Bits 24-31: Driver number |
Exit | |
---|---|
R0 | Mode number/selector to use |
R4 | 0 |
- | All other registers preserved |
This call allows a GraphicsV driver to override the choice of screen mode in certain situations, e.g. on driver startup, or the default mode used by the Wimp. For example, a device with a fixed size LCD may want to select a mode which fills the display.
The kernel issues this call from within OS_ReadSysInfo 1 . However However, it will only issue it under certain circumstances – see the OS_ReadSysInfo page for details.
If the mode returned refers to a mode definition which is not one of the kernel’s numbered modes, a suitable mode definition needs to have been loaded, e.g. from a ResourceFS based built in MDF. Service_ModeExtension can then subsequently find it and provide the relevant settings. If there is not a mode definition file, a custom Service_ModeExtension response needs to be provided.