[Qt-embedded-interest] Linux frame buffer and screen resolutions

[Anil H]

HI,

Thanks for the info
As you have rightly mentioned there was an issue in the driver which was
reading out the entire framebuffer to display even though the mode was
changed.
Currently I have done a workaround and it works fine.

Thanks and regards
Anil

On Fri, Jun 5, 2009 at 12:24 AM, <thomas.cooksey at nokia.com> wrote:

> > The line length provided by ioctl( ,FBIOGET_FSCREENINFO,...,finfo)
> > This length is Fixed screen info which maximum supported by device
> > finfo.linelength is 1280*2 since max width supported is 1280 pixels
> > and number of bytes per line is 1280*2
> >
> > Where as ( ,FBIOGET_VSCREENINFO,...,vinfo)
> > which gives dynamic(variable) screen info in which xres is 720 which
> > is the correct value. So while calculating pitch 720*bytes_per_pixel
> > is to be considered
>
> What framebuffer driver are you using? The fbdev kernel interface is
> designed for fixed-size framebuffers. When you change modes, the size
> of the framebuffer remains the same, it's just that you don't use all
> of it. Usually there's a kernel/module parameter you can use to set
> the size of this framebuffer - but once the module is loaded, it's size
> is fixed. That's why the pitch or line step is stored in the fixed data.
>
> It sounds like a bug in your framebuffer driver which is reading the
> framebuffer out to the display with a different pitch to what it's
> reporting to userspace. Either fix your kerenl driver, or you can easily
> work round the bug by patching qscreenlinuxfb_qws.cpp.
>
>
> Cheers,
>
> Tom
>
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