drm/ttm: return ENOSPC from ttm_bo_mem_space v3

Only convert it to ENOMEM in ttm_bo_validate.

This allows ttm_bo_validate to distinguish between an out of memory
situation and just out of space in a placement domain.

v2: improve commit message
v3: fix kerneldoc typos

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Zack Rusin <zack.rusin@broadcom.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240112125158.2748-3-christian.koenig@amd.com

Author: ChristianKoenigAMD

drivers/gpu/drm/ttm/ttm_bo.c

@@ -770,7 +770,7 @@ static int ttm_bo_mem_force_space(struct ttm_buffer_object *bo,
  * This function may sleep while waiting for space to become available.
  * Returns:
  * -EBUSY: No space available (only if no_wait == 1).
- * -ENOMEM: Could not allocate memory for the buffer object, either due to
+ * -ENOSPC: Could not allocate space for the buffer object, either due to
  * fragmentation or concurrent allocators.
  * -ERESTARTSYS: An interruptible sleep was interrupted by a signal.
  */
@@ -830,7 +830,7 @@ int ttm_bo_mem_space(struct ttm_buffer_object *bo,
 			goto error;
 	}
 
-	ret = -ENOMEM;
+	ret = -ENOSPC;
 	if (!type_found) {
 		pr_err(TTM_PFX "No compatible memory type found\n");
 		ret = -EINVAL;
@@ -916,6 +916,9 @@ int ttm_bo_validate(struct ttm_buffer_object *bo,
 		return -EINVAL;
 
 	ret = ttm_bo_move_buffer(bo, placement, ctx);
+	/* For backward compatibility with userspace */
+	if (ret == -ENOSPC)
+		return -ENOMEM;
 	if (ret)
 		return ret;