On 13/7/24 17:56, SamJakob wrote:
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 <m...@samjakob.com> --- hw/display/bcm2835_fb.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/hw/display/bcm2835_fb.c b/hw/display/bcm2835_fb.c index e40ed2d2e1..650db3da82 100644 --- a/hw/display/bcm2835_fb.c +++ b/hw/display/bcm2835_fb.c @@ -145,7 +145,7 @@ static bool fb_use_offsets(BCM2835FBConfig *config) * viewport size is larger than the physical screen. (It doesn't * prevent the guest setting this silly viewport setting, though...) */ - return config->xres_virtual > config->xres && + return config->xres_virtual > config->xres || config->yres_virtual > config->yres; }
Reviewed-by: Philippe Mathieu-Daudé <phi...@linaro.org>
