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

[Frediano Ziglio <freddy77@xxxxxxxxx>]

Modern notebook support 136x768 resolution. The resolution width is
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 ?
- 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?

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,
                                                             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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