drm/radeon: add new getparam for number of backends.

This allows userspace to work out how many DBs there are
for conditional rendering to work.
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/radeon_drv.c

@@ -49,7 +49,7 @@
  * - 2.6.0 - add tiling config query (r6xx+), add initial HiZ support (r300->r500)
  *   2.7.0 - fixups for r600 2D tiling support. (no external ABI change), add eg dyn gpr regs
  *   2.8.0 - pageflip support, r500 US_FORMAT regs. r500 ARGB2101010 colorbuf, r300->r500 CMASK, clock crystal query
- *   2.9.0 - r600 tiling (s3tc,rgtc) working, SET_PREDICATION packet 3 on r600 + eg
+ *   2.9.0 - r600 tiling (s3tc,rgtc) working, SET_PREDICATION packet 3 on r600 + eg, backend query
  */
 #define KMS_DRIVER_MAJOR	2
 #define KMS_DRIVER_MINOR	9

drivers/gpu/drm/radeon/radeon_kms.c

@@ -205,6 +205,17 @@ int radeon_info_ioctl(struct drm_device *dev, void *data, struct drm_file *filp)
 		/* return clock value in KHz */
 		value = rdev->clock.spll.reference_freq * 10;
 		break;
+	case RADEON_INFO_NUM_BACKENDS:
+		if (rdev->family >= CHIP_CEDAR)
+			value = rdev->config.evergreen.max_backends;
+		else if (rdev->family >= CHIP_RV770)
+			value = rdev->config.rv770.max_backends;
+		else if (rdev->family >= CHIP_R600)
+			value = rdev->config.r600.max_backends;
+		else {
+			return -EINVAL;
+		}
+		break;
 	default:
 		DRM_DEBUG_KMS("Invalid request %d\n", info->request);
 		return -EINVAL;

include/drm/radeon_drm.h

@@ -908,6 +908,7 @@ struct drm_radeon_cs {
 #define RADEON_INFO_WANT_HYPERZ		0x07
 #define RADEON_INFO_WANT_CMASK		0x08 /* get access to CMASK on r300 */
 #define RADEON_INFO_CLOCK_CRYSTAL_FREQ	0x09 /* clock crystal frequency */
+#define RADEON_INFO_NUM_BACKENDS	0x0a /* DB/backends for r600+ - need for OQ */
 
 struct drm_radeon_info {
 	uint32_t		request;