NOTE: As of Linux kernel 2.6.10, there is a generic ACPI video driver called "video" that lives at
/proc/acpi/video . This may be a suitable alternative to controlling video with toshiba_acpi.
The driver uses a standard Toshiba HCI register to read the video output status. In contrast, when altering the output it uses the
\_SB_.VALX.DSSX ACPI method. For the Toshiba Libretto L series, on which the driver was developed, it was found that setting the HCI register alone is not sufficient. Likely this is because the graphics chip settings need to be changed also, and the ACPI method takes care of this.
The problem seems to be that the
\_SB_.VALX.DSSX method does not exist on all Toshiba machines with ACPI. The symptom is that you write to /proc/acpi/toshiba/video, but it has no effect on the status. Currently the driver does not check the result of the
\_SB_.VALX.DSSX method call, so no error is reported.
In the ToshibaAcpi document in the section "More Disassembly Practice", someone has confirmed that
\_SB_.VALX.DSSX doesn't exist on his machine. The reporter says that
\_SB.PCI0.PCI1.VGA.CRT._DSS, etc., presumably lower-level methods, can be used instead. However, the device location seems to be hard-coded in the method names. Using this may require per-model adjustments or introspection of the ACPI method tree.