[Spice-devel] [PATCH] miniport/qxl: FillVideoMode: only allow word aligned strides

[Christophe Fergeau]

On Thu, Oct 11, 2012 at 12:23:21PM +0200, Alon Levy wrote:
> This is a pixman requirement. If it isn't enforced spice crashes, qemu
> with it. That should be fixed, but there is no simple way to allow for
> non word aligned strides, and the only down side is that for 16 bit
> modes we will require even widths. And we already have the same
> implementation detail in the X driver, only there it is a multiple of 8,
> not 4.
> ---
>  miniport/qxl.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/miniport/qxl.c b/miniport/qxl.c
> index 55e55d3..f177d91 100644
> --- a/miniport/qxl.c
> +++ b/miniport/qxl.c
> @@ -469,17 +469,24 @@ VP_STATUS FillVidModeInfo(VIDEO_MODE_INFORMATION *pMode, ULONG xres, ULONG yres,
>  /* Fills given video mode structure */
>  VP_STATUS FillVidModeInfo(VIDEO_MODE_INFORMATION *pMode, ULONG xres, ULONG yres, ULONG bpp, ULONG index)
>  {
> +    unsigned bytes_pp = (bpp + 7) / 8;
> +
>      if (xres <= 0 || yres <= 0)
>          return ERROR_INVALID_DATA;
>  
>      VideoPortZeroMemory(pMode, sizeof(VIDEO_MODE_INFORMATION));
>  
> +    /* Honor pixmap's stride % 4 == 0 limitation. Pixmap is used by spice-server. */
> +    if (xres * bytes_pp % 4 != 0) {
> +        xres = ((xres * bytes_pp) & ~0x3) / bytes_pp;
> +    }
> +
>      /*Common entries*/
>      pMode->Length                       = sizeof(VIDEO_MODE_INFORMATION);
>      pMode->ModeIndex                    = index;
>      pMode->VisScreenWidth               = xres;
>      pMode->VisScreenHeight              = yres;
> -    pMode->ScreenStride                 = xres * ((bpp + 7) / 8);
> +    pMode->ScreenStride                 = xres * bytes_pp;

Shouldn't we keep VisScreenWidth unchanged, and just round ScreenStride up
so that it's a multiple of 4? Ie don't change xres at all, and set
ScreenStride to (xres * bytes_pp + 3)/4.

Christophe
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