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

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 15 Mar 2013, Frediano Ziglio wrote:
> Modern notebook support 136x768 resolution. The resolution width is
                            ^this can't be right

> not multiple of 16 causing some problems.
> 
> Qemu VGA emulation require width resolution to be multiple of 8.
> 
> VNC implementation require width resolution to be multiple of 16.
> 
> This patch remove these limits. Was tested with a Windows machine with
> standard vga and 1366x768 as resolution. I had to update vgabios as
> version in qemu (pc-bios/vgabios-stdvga.bin) is quite old. I also had
> to add some patches on top of VGABIOS 0.7a to add some new
> resolutions.
> 
> I have some doubt about this patch
> - are other UI (sdl, cocoa, qxl) happy if resolution is not multiple of 16 ?

It's worth testing at least sdl and gtk


> - scanline is computed exactly without any alignment (so 1366 8 bit is
> 1366 bytes) while getting vesa information from a laptop it seems to
> use some kind of alignment (if became 0x580 which is 1408 bytes).
> Perhaps should I change either VGABIOS and Qemu to make this
> alignment?

I don't think there are any requirements to set the scanline bigger than
width*bpp


> Signed-off-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxxx>
> 
> ---
>  hw/vga.c |    2 +-
>  ui/vnc.c |   27 +++++++++++++--------------
>  2 files changed, 14 insertions(+), 15 deletions(-)
> 
> diff --git a/hw/vga.c b/hw/vga.c
> index 1caf23d..d229f06 100644
> --- a/hw/vga.c
> +++ b/hw/vga.c
> @@ -651,7 +651,7 @@ void vbe_ioport_write_data(void *opaque, uint32_t
> addr, uint32_t val)
>              }
>              break;
>          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;
> diff --git a/ui/vnc.c b/ui/vnc.c
> index ff4e2ae..328d14d 100644
> --- a/ui/vnc.c
> +++ b/ui/vnc.c
> @@ -907,26 +907,27 @@ static int vnc_update_client(VncState *vs, int 
> has_dirty)
>          for (y = 0; y < height; y++) {
>              int x;
>              int last_x = -1;
> -            for (x = 0; x < width / 16; x++) {
> -                if (test_and_clear_bit(x, vs->dirty[y])) {
> +            for (x = 0; x < width; x += 16) {
> +                if (test_and_clear_bit(x/16, vs->dirty[y])) {
>                      if (last_x == -1) {
>                          last_x = x;
>                      }
>                  } else {
>                      if (last_x != -1) {
> -                        int h = find_and_clear_dirty_height(vs, y, last_x, x,
> +                        int h = find_and_clear_dirty_height(vs, y,
> last_x/16, x/16,

your mail client must have messed up this patch

>                                                              height);
> 
> -                        n += vnc_job_add_rect(job, last_x * 16, y,
> -                                              (x - last_x) * 16, h);
> +                        n += vnc_job_add_rect(job, last_x, y,
> +                                              (x - last_x), h);
>                      }
>                      last_x = -1;
>                  }
>              }
>              if (last_x != -1) {
> -                int h = find_and_clear_dirty_height(vs, y, last_x, x, 
> height);
> -                n += vnc_job_add_rect(job, last_x * 16, y,
> -                                      (x - last_x) * 16, h);
> +                int h = find_and_clear_dirty_height(vs, y, last_x/16,
> x/16, height);
> +                if (x > width) x = width;
> +                n += vnc_job_add_rect(job, last_x, y,
> +                                      (x - last_x), h);
>              }
>          }
> 
> @@ -1771,7 +1772,7 @@ static void framebuffer_update_request(VncState
> *vs, int incremental,
>                                         int w, int h)
>  {
>      int i;
> -    const size_t width = ds_get_width(vs->ds) / 16;
> +    const size_t width = (ds_get_width(vs->ds)+15) / 16;
> 
>      if (y_position > ds_get_height(vs->ds))
>          y_position = ds_get_height(vs->ds);
> @@ -2595,10 +2596,6 @@ static int vnc_refresh_server_surface(VncDisplay *vd)
>       * Check and copy modified bits from guest to server surface.
>       * Update server dirty map.
>       */
> -    cmp_bytes = 64;
> -    if (cmp_bytes > vnc_server_fb_stride(vd)) {
> -        cmp_bytes = vnc_server_fb_stride(vd);
> -    }
>      if (vd->guest.format != VNC_SERVER_FB_FORMAT) {
>          int width = pixman_image_get_width(vd->server);
>          tmpbuf = qemu_pixman_linebuf_create(VNC_SERVER_FB_FORMAT, width);
> @@ -2619,8 +2616,10 @@ static int vnc_refresh_server_surface(VncDisplay *vd)
>              }
>              server_ptr = server_row;
> 
> -            for (x = 0; x + 15 < width;
> +            cmp_bytes = 64;
> +            for (x = 0; x < width;
>                      x += 16, guest_ptr += cmp_bytes, server_ptr += 
> cmp_bytes) {
> +                if (width - x < 16) cmp_bytes = 4 * (width - x);
>                  if (!test_and_clear_bit((x / 16), vd->guest.dirty[y]))
>                      continue;
>                  if (memcmp(server_ptr, guest_ptr, cmp_bytes) == 0)
> -- 
> 1.7.10.4
> 

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