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hw/display/bcm2835_fb: Fix handling of virtual framebuffer

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The raspi framebuffir in bcm2835_fb supports the definition
of a virtual "viewport", which is smaller than the full
physical framebuffer size and at an adjustable offset within
it. Only the viewport area is sent to the screen. This allows
the guest to do things like double buffering, or scrolling
by adjusting the viewport origin. Currently QEMU doesn't
implement this at all.

Add support for this feature:
 * the property mailbox code needs to distinguish the
   virtual width/height from the physical width/height
 * the framebuffer code needs to do something with the
   virtual width/height/origin information

Note that the wiki documentation on the semantics of the
virtual and physical height and width has it the wrong way
around -- the virtual size is the size of the allocated
buffer, and the physical size is the size of the display,
so the virtual size is always the same as or larger than
the physical.

If the viewport size is set smaller than the physical
screen size, we ignore the viewport settings completely
and just display the physical screen area.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20180814144436.679-7-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2018-08-24 13:17:49 +01:00
parent 9a1f03f4ee
commit 01f18af98b
3 changed files with 41 additions and 14 deletions
Download patch file Download diff file Expand all files Collapse all files

6
include/hw/display/bcm2835_fb.h
View file

@ -62,7 +62,8 @@ void bcm2835_fb_reconfigure(BCM2835FBState *s, BCM2835FBConfig *newconfig);
*/
static inline uint32_t bcm2835_fb_get_pitch(BCM2835FBConfig *config)
{
return config->xres * (config->bpp >> 3);
uint32_t xres = MAX(config->xres, config->xres_virtual);
return xres * (config->bpp >> 3);
}
/**
@ -71,7 +72,8 @@ static inline uint32_t bcm2835_fb_get_pitch(BCM2835FBConfig *config)
*/
static inline uint32_t bcm2835_fb_get_size(BCM2835FBConfig *config)
{
return config->yres * bcm2835_fb_get_pitch(config);
uint32_t yres = MAX(config->yres, config->yres_virtual);
return yres * bcm2835_fb_get_pitch(config);
}
#endif