vgaarb: Add user selectability of the number of GPUS in a system

Update the VGA Arbiter to allow the user to select the number
of GPU's supported in a system.

v2: simplify setting of MAX_USER_CARDS, revert back to original default of 16
Signed-off-by: NMike Travis <travis@sgi.com>
LKML-Reference: <4B68D51D.6090401@sgi.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Robin Holt <holt@sgi.com>
Cc: Jack Steiner <steiner@sgi.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: David Airlie <airlied@linux.ie>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

drivers/gpu/vga/Kconfig

@@ -8,3 +8,11 @@ config VGA_ARB
 	  are accessed at same time they need some kind of coordination. Please
 	  see Documentation/vgaarbiter.txt for more details. Select this to
 	  enable VGA arbiter.
+
+config VGA_ARB_MAX_GPUS
+	int "Maximum number of GPUs"
+	default 16
+	depends on VGA_ARB
+	help
+	  Reserves space in the kernel to maintain resource locking for
+	  multiple GPUS.  The overhead for each GPU is very small.

drivers/gpu/vga/vgaarb.c

@@ -688,7 +688,7 @@ EXPORT_SYMBOL(vga_client_register);
  * the arbiter.
  */
 
-#define MAX_USER_CARDS         16
+#define MAX_USER_CARDS         CONFIG_VGA_ARB_MAX_GPUS
 #define PCI_INVALID_CARD       ((struct pci_dev *)-1UL)
 
 /*