Re: [Qemu-devel] [RFC PATCH] vga: Start supporting resolution not multiple of 16 correctly.

[Frediano Ziglio]

2013/7/23 Gerd Hoffmann <address@hidden>

  Hi,

> Tested-by: Fabio Fantoni <address@hidden>
>
> I tested it for a long time with spice on xen (because qxl will be fully
> working only after adding SSE support on hvm domUs). It works, I think
> it is good to add this and the respective vgabios patch on upstream.

>>          case VBE_DISPI_INDEX_XRES:
>> -            if ((val <= VBE_DISPI_MAX_XRES) && ((val & 7) == 0)) {
>> +            if ((val <= VBE_DISPI_MAX_XRES) && ((val & 1) == 0)) {
>>                  s->vbe_regs[s->vbe_index] = val;
>>              }
>>              break;

It's not that simple.  With 32bit depths common today it will work fine,
but for lower depths (especially those lower than 8bit) this will give
you broken scanline alignment.

cheers,
  Gerd

In the card I tested the scanline is keep aligned but for this reason is not directly computed by maxx * bits but is something bigger.

Frediano