Who can explain the diff between Xserver-1.6.4 version and >1.7 version about the ExaGetPixmapAddress?

[Cui, Hunk]

Hi, Maarten,
	You can see my attachment screenshot, in this example, when run to the line 177-178, the pPixData is 0xb62b000, pExaScr->info->memoryBase is 0xb5e2b000,pExaScr->info->memorySize is 17825792, if only have "<", the judge will not come into existence. 
	You can try it. If not come into existence. The fb_ptr address value is 0x0.

Thanks,
Hunk Cui


-----Original Message-----
From: Maarten Maathuis [mailto:madman2003 at gmail.com] 
Sent: Wednesday, June 09, 2010 5:47 PM
To: Cui, Hunk
Cc: xorg-devel at lists.x.org; Huang, FrankR; Writer, Tim; Torres, Rigo
Subject: Re: Who can explain the diff between Xserver-1.6.4 version and >1.7 version about the ExaGetPixmapAddress?

On Wed, Jun 9, 2010 at 10:23 AM, Cui, Hunk <Hunk.Cui at amd.com> wrote:
> Hi, Maarten,
>
>         As your commit:
> http://cgit.freedesktop.org/xorg/xserver/commit/?id=12aeddf5ad41902a180f8108623f356642b3e911
>
>         About Scratch pixmap with gpu memory – Framebuffer. Now in > 1.7
> version, the exaModifyPixmapHeader function have been become
> exaModifyPixmapHeader_classic (
> http://cgit.freedesktop.org/xorg/xserver/tree/exa/exa_classic.c?id=ac7ac913fd98ea359c05c89968ab53a3223615b4
> Line 144).
>
>         When I debug to this point (my AMD xf86-video-geode), the line
> 171-172, why only have the “<” judge. For general, I think “((CARD8
> *)pPixData - pExaScr->info->memoryBase) <= pExaScr->info->memorySize)”,
> because rotate_mem offset should equal to the pExaScr->info->memorySize
> (e.g: displayed frame buffer). If only have the “<”, It will not go into
> this judge, so the fb_ptr address value is 0x0, then the value will affect
> the exaGetPixmapOffset function (in exa.c
> http://cgit.freedesktop.org/xorg/xserver/tree/exa/exa.c?id=ac7ac913fd98ea359c05c89968ab53a3223615b4
> line 62) about “return (CARD8 *)pExaPixmap->fb_ptr -
> pExaScr->info->memoryBase”, the range will be exceed, if run the
> driver_do_composite (It is lx_do_composite in our geode_driver), the
> dstOffset is a error value.
>
>         Could you explain this issue? Let me know why only have “<”.

If your memory base is 20000, your offscreen memory size is 10000,
then 20000 to 29999 are valid addresses. If you enter 30000 - 10000 <=
20000, then that would be true, which is wrong, that's why it's just
"<", because addressing starts from 0 not 1.

>
> Thanks,
>
> Hunk Cui
>
>



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