drm/i915: Fix docbook descriptions for i915_cmd_parser

Fixes the following htmldocs warnings:
drivers/gpu/drm/i915/i915_cmd_parser.c:1420: warning: Excess function parameter 'trampoline' description in 'intel_engine_cmd_parser'
drivers/gpu/drm/i915/i915_cmd_parser.c:1420: warning: Function parameter or member 'jump_whitelist' not described in 'intel_engine_cmd_parser'
drivers/gpu/drm/i915/i915_cmd_parser.c:1420: warning: Function parameter or member 'shadow_map' not described in 'intel_engine_cmd_parser'
drivers/gpu/drm/i915/i915_cmd_parser.c:1420: warning: Function parameter or member 'batch_map' not described in 'intel_engine_cmd_parser'
drivers/gpu/drm/i915/i915_cmd_parser.c:1420: warning: Excess function parameter 'trampoline' description in 'intel_engine_cmd_parser'
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210421120353.544518-1-maarten.lankhorst@linux.intel.comReviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_cmd_parser.c

@@ -1369,6 +1369,20 @@ static int check_bbstart(u32 *cmd, u32 offset, u32 length,
 	return 0;
 }
 
+/**
+ * intel_engine_cmd_parser_alloc_jump_whitelist() - preallocate jump whitelist for intel_engine_cmd_parser()
+ * @batch_length: length of the commands in batch_obj
+ * @trampoline: Whether jump trampolines are used.
+ *
+ * Preallocates a jump whitelist for parsing the cmd buffer in intel_engine_cmd_parser().
+ * This has to be preallocated, because the command parser runs in signaling context,
+ * and may not allocate any memory.
+ *
+ * Return: NULL or pointer to a jump whitelist, or ERR_PTR() on failure. Use
+ * IS_ERR() to check for errors. Must bre freed() with kfree().
+ *
+ * NULL is a valid value, meaning no allocation was required.
+ */
 unsigned long *intel_engine_cmd_parser_alloc_jump_whitelist(u32 batch_length,
 							    bool trampoline)
 {
@@ -1401,7 +1415,9 @@ unsigned long *intel_engine_cmd_parser_alloc_jump_whitelist(u32 batch_length,
  * @batch_offset: byte offset in the batch at which execution starts
  * @batch_length: length of the commands in batch_obj
  * @shadow: validated copy of the batch buffer in question
- * @trampoline: whether to emit a conditional trampoline at the end of the batch
+ * @jump_whitelist: buffer preallocated with intel_engine_cmd_parser_alloc_jump_whitelist()
+ * @shadow_map: mapping to @shadow vma
+ * @batch_map: mapping to @batch vma
  *
  * Parses the specified batch buffer looking for privilege violations as
  * described in the overview.