Add an isa device for SGA

This patch adds a dummy legacy ISA device whose responsibility is to
deploy sgabios, an option rom for a serial graphics adapter.
The proposal is that this device is always-on when -nographics,
but can otherwise be enable in any setup when -device sga is used.

[v2: suggestions on qdev by Markus ]
[v3: cleanups and documentation, per list suggestions ]

Signed-off-by: Glauber Costa <glommer@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/hw/pc.c b/hw/pc.c
index 810619756b..a3e8539dc6 100644
--- a/hw/pc.c
+++ b/hw/pc.c
@@ -1070,6 +1070,15 @@ void pc_vga_init(PCIBus *pci_bus)
             isa_vga_init();
         }
     }
+
+    /*
+     * sga does not suppress normal vga output. So a machine can have both a
+     * vga card and sga manually enabled. Output will be seen on both.
+     * For nographic case, sga is enabled at all times
+     */
+    if (display_type == DT_NOGRAPHIC) {
+        isa_create_simple("sga");
+    }
 }
 
 static void cpu_request_exit(void *opaque, int irq, int level)