From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1KiL1T-0006XV-K5 for qemu-devel@nongnu.org; Tue, 23 Sep 2008 23:26:39 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1KiL1S-0006XJ-HD for qemu-devel@nongnu.org; Tue, 23 Sep 2008 23:26:39 -0400 Received: from [199.232.76.173] (port=35540 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1KiL1S-0006XG-DO for qemu-devel@nongnu.org; Tue, 23 Sep 2008 23:26:38 -0400 Received: from mail-gx0-f19.google.com ([209.85.217.19]:59482) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1KiL1S-0004cs-9W for qemu-devel@nongnu.org; Tue, 23 Sep 2008 23:26:38 -0400 Received: by gxk12 with SMTP id 12so5545334gxk.10 for ; Tue, 23 Sep 2008 20:26:37 -0700 (PDT) Message-ID: <48D9B333.90200@codemonkey.ws> Date: Tue, 23 Sep 2008 22:25:39 -0500 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH 3 of 6] vga shared buffer References: <48CA51E6.1010305@eu.citrix.com> <48CE8819.8070204@codemonkey.ws> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org andrzej zaborowski wrote: > 2008/9/15 Anthony Liguori : > >> Stefano Stabellini wrote: >> >>> Signed-off-by: Stefano Stabellini >>> >>> >> I need to carve out some time to test this series and think about whether it >> can be done without adding a new DisplayState hook. I should be able to >> respond or apply within a few days. >> > > Any news? I think this change makes sense and it can help remove the > DIRECT_VRAM hack from vmware_vga.c. > > >> I'm concerned about the complexity this adds to back-ends. It's not clear >> to me whether the performance justifies the added complexity. >> > > One way to simplify this and everything else is use Stefano's code to > stop the backends (SDL, VNC) from managing the framebuffer altogether > and only support what these patches call shared buffer. This is sort of what I've been thinking about. If we're going to do this at all, we should move to a model where the backends stop managing the framebuffers completely. > Then if the > given backed doesn't support given colorspace conversion in hardware, > it's its call to implement this, it could unify the color conversion > in qemu more generally. The drawback is it's hard to support weird > colorspaces like those supported by OMAP2 display susbsystem, and even > harder to do features like overlaid framebuffers with different > colorspaces (but it's not currently implemented anyway). > It's slightly less optimal when you aren't going from a real framebuffer. For instance, right now when in VGA planar mode, we're able to basically write pixels in the SDL buffer directly from the mmio callbacks. If we switched to having the VGA devices manage their buffers, we would have to write to a buffer and then rely on SDL conversion functions to flip the buffer. I don't know that it's really worth optimizing for things like VGA planar mode but I think that's really the trade off that we're making. Regards, Anthony Liguori > Regards > > >