hw/display/bcm2835_fb: fix fb_use_offsets condition

It is common practice when implementing double-buffering on VideoCore
to do so by multiplying the height of the virtual buffer by the
number of virtual screens desired (i.e., two - in the case of
double-bufferring).

At present, this won't work in QEMU because the logic in
fb_use_offsets require that both the virtual width and height exceed
their physical counterparts.

This appears to be unintentional/a typo and indeed the comment
states; "Experimentally, the hardware seems to do this only if the
viewport size is larger than the physical screen".  The
viewport/virtual size would be larger than the physical size if
either virtual dimension were larger than their physical counterparts
and not necessarily both.

Signed-off-by: SamJakob <me@samjakob.com>
Message-id: 20240713160353.62410-1-me@samjakob.com
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
1 file changed