vga: disable default VGA if appropriate -device is used

This is a partial revert of commits a369da5f (vga: improve VGA logic,
committed 2012-01-22) and c5bd4f3d (vga: fix -nodefaults -device VGA,
2012-01-24) which broke command-line option parsing in different ways.

Since commit a369da5f it has become impossible to specify a VGA device
entirely with QemuOpts-enabled options, i.e. without needing an explicit
"-vga none".

In addition, until commit c5bd4f3d -nodefaults would not disable the device
you specified with the legacy "-vga" option, independent of the order.
Since commit c5bd4f3d QEMU -nodefaults will override a previous -vga
option.

I did not reintroduce machine->no_vga.  Boards can simply ignore the
vga_interface_type variable, and most will indeed do so.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>

vl.c

@@ -273,6 +273,7 @@ static int default_monitor = 1;
 static int default_floppy = 1;
 static int default_cdrom = 1;
 static int default_sdcard = 1;
+static int default_vga = 1;
 
 static struct {
     const char *driver;
@@ -288,6 +289,12 @@ static struct {
     { .driver = "virtio-serial-pci",    .flag = &default_virtcon   },
     { .driver = "virtio-serial-s390",   .flag = &default_virtcon   },
     { .driver = "virtio-serial",        .flag = &default_virtcon   },
+    { .driver = "VGA",                  .flag = &default_vga       },
+    { .driver = "isa-vga",              .flag = &default_vga       },
+    { .driver = "cirrus-vga",           .flag = &default_vga       },
+    { .driver = "isa-cirrus-vga",       .flag = &default_vga       },
+    { .driver = "vmware-svga",          .flag = &default_vga       },
+    { .driver = "qxl-vga",              .flag = &default_vga       },
 };
 
 static void res_free(void)
@@ -2277,7 +2284,7 @@ int main(int argc, char **argv, char **envp)
     const char *loadvm = NULL;
     QEMUMachine *machine;
     const char *cpu_model;
-    const char *vga_model = NULL;
+    const char *vga_model = "none";
     const char *pid_file = NULL;
     const char *incoming = NULL;
 #ifdef CONFIG_VNC
@@ -2709,6 +2716,7 @@ int main(int argc, char **argv, char **envp)
                 break;
             case QEMU_OPTION_vga:
                 vga_model = optarg;
+                default_vga = 0;
                 break;
             case QEMU_OPTION_g:
                 {
@@ -3118,7 +3126,7 @@ int main(int argc, char **argv, char **envp)
                 default_floppy = 0;
                 default_cdrom = 0;
                 default_sdcard = 0;
-                vga_model = "none";
+                default_vga = 0;
                 break;
             case QEMU_OPTION_xen_domid:
                 if (!(xen_available())) {
@@ -3488,14 +3496,11 @@ int main(int argc, char **argv, char **envp)
     if (foreach_device_config(DEV_DEBUGCON, debugcon_parse) < 0)
         exit(1);
 
-    /* must be after qdev registration but before machine init */
-    if (vga_model) {
-        select_vgahw(vga_model);
-    } else if (cirrus_vga_available()) {
-        select_vgahw("cirrus");
-    } else {
-        select_vgahw("none");
+    /* If no default VGA is requested, the default is "none".  */
+    if (default_vga && cirrus_vga_available()) {
+        vga_model = "cirrus";
     }
+    select_vgahw(vga_model);
 
     if (qemu_opts_foreach(qemu_find_opts("device"), device_help_func, NULL, 0) != 0)
         exit(0);