Fully disable poulsbo detearing code at run time rather than as a compile time option

[Colin Ian King]

Ubuntu-hardy-lum, netbook-lpia branch.

The psb de-tearing code is currently a compile time option and the default is to have de-tearing enabled by #defining PSB_DETEAR in psb_drv.h. Some of the de-tearing code path can be disabled with the psb module parameter detear=0 but this does not fully disable all the of de-tearing code paths.

The the semantics of the psb detear module parameter should totally disable the de-tearing code paths so the code is functionally identical to compiling the code with PSB_DETEAR disabled.

This will enable the driver to totally disable de-tearing at module load time rather than at compile time.

Disabling de-tearing is a workaround to a couple of known issues on some hardware:

1) Playing MS-MPEG4 encoded video with Xv which causes X to crash
2) Playing a video while the screen is turned off (with DPMPS or
xrandr) which causes X to hang

..so it is advantageous to be able to enable/disable de-tearing at run time for different hardware variants where necessary.

[Colin Ian King (colin-king)]

Committed: http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-hardy-lum.git;a=commit;h=16163f4ba2ae13dc556d3f09d9d1b68fd78f3370