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Re: [Qemu-devel] [PATCH 6/8] hw/display/bcm2835_fb: Fix handling of virt

From: Richard Henderson
Subject: Re: [Qemu-devel] [PATCH 6/8] hw/display/bcm2835_fb: Fix handling of virtual framebuffer
Date: Thu, 23 Aug 2018 21:44:07 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1

On 08/14/2018 07:44 AM, Peter Maydell wrote:
> 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 <address@hidden>
> ---
>  include/hw/display/bcm2835_fb.h |  6 ++++--
>  hw/display/bcm2835_fb.c         | 28 ++++++++++++++++++++++------
>  hw/misc/bcm2835_property.c      | 21 +++++++++++++++------
>  3 files changed, 41 insertions(+), 14 deletions(-)

Reviewed-by: Richard Henderson <address@hidden>


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