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

[Uri Lublin]

On 10/11/2012 12:23 PM, 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;
> +    }
> +

Hi Alon,

I think this calculation is wrong. For example assume xres=3 and bytes_pp=5
     xres = (15 & ~0x3) / 5   =   12 / 5  =  2

but now xres * bytes_pp = 10

Are there assumptions I'm missing ?

Thanks,
     Uri.