drm: radeon: implement RADEON_PARAM_SCRATCH_OFFSET getparam

When this succeeds, userspace can read the scratch register contents from th    mapped writeback page directly.

Signed-off-by: Dave Airlie <airlied@linux.ie>

diff --git a/drivers/char/drm/radeon_state.c b/drivers/char/drm/radeon_state.c
index 99589fe..0433ff8 100644 (file)
--- a/drivers/char/drm/radeon_state.c
+++ b/drivers/char/drm/radeon_state.c
@@ -2987,7 +2987,11 @@ static int radeon_cp_getparam(DRM_IOCTL_ARGS)
        case RADEON_PARAM_GART_TEX_HANDLE:
                value = dev_priv->gart_textures_offset;
                break;
-       
+       case RADEON_PARAM_SCRATCH_OFFSET:
+               if (!dev_priv->writeback_works)
+                       return DRM_ERR(EINVAL);
+               value = RADEON_SCRATCH_REG_OFFSET;
+               break;
        case RADEON_PARAM_CARD_TYPE:
                if (dev_priv->flags & CHIP_IS_PCIE)
                        value = RADEON_CARD_PCIE;