Xserver res support

[Adam Jackson]

On 4/6/11 1:33 PM, display wrote:

> I am wondering whether X server has any built in checks and balances to
> limit any resolutions. Can someone shed light on this? Trying to
> understand X limitations before planning to support smaller resolutions
> (320x240, 640x320, 640x240 etc) via X driver.

The server itself has only two intrinsic limitations on resolution 
sizes: they must be at least 1x1, and must not be larger than 32767x32767.

Beyond that, the server offers a relatively rich set of filtering logic 
that drivers may hook into to eliminate certain modes based on various 
criteria: memory bandwidth usage, minimum and maximum pitch, dotclock, 
horizontal and vertical sync ranges, etc.  Whether a given mode is 
supported or not ultimately depends on the driver.

> Btw, if wanted to use default "vesa" or "vga" driver, does it support
> resolutions smaller than 640x480 given underlying firmware (VBIOS)
> support them?

The vga driver - which is dead, and was never very good - has no BIOS 
interaction at all.  The supported modes are described in its 
documentation, but don't bother trying to use it.

The vesa driver supports whatever modes the video BIOS claims to 
support.  Some earlier versions of the vesa driver had an arbitrary 
upper limit of 2048x2048, but this is fixed in vesa 2.3.0 and later.

- ajax