Add a note about the two-step process.
v2(Tvrtko):
- Also document the other method of just passing in a buffer which is
large enough, which avoids two ioctl calls. Can make sense for
smaller query items.
Suggested-by: Daniel Vetter <daniel@xxxxxxxx>
Signed-off-by: Matthew Auld <matthew.auld@xxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
Cc: Jordan Justen <jordan.l.justen@xxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx>
Cc: Kenneth Graunke <kenneth@xxxxxxxxxxxxx>
Cc: Jason Ekstrand <jason@xxxxxxxxxxxxxx>
Cc: Dave Airlie <airlied@xxxxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: mesa-dev@xxxxxxxxxxxxxxxxxxxxx
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
---
include/uapi/drm/i915_drm.h | 61 ++++++++++++++++++++++++++++++-------
1 file changed, 50 insertions(+), 11 deletions(-)
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index d79b51c12ff2..12f375c52317 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -2218,14 +2218,23 @@ struct drm_i915_perf_oa_config {
__u64 flex_regs_ptr;
};
+/**
+ * struct drm_i915_query_item - An individual query for the kernel to process.
+ *
+ * The behaviour is determined by the @query_id. Note that exactly what
+ * @data_ptr is also depends on the specific @query_id.
+ */
struct drm_i915_query_item {
+ /** @query_id: The id for this query */
__u64 query_id;
#define DRM_I915_QUERY_TOPOLOGY_INFO 1
#define DRM_I915_QUERY_ENGINE_INFO 2
#define DRM_I915_QUERY_PERF_CONFIG 3
/* Must be kept compact -- no holes and well documented */
- /*
+ /**
+ * @length:
+ *
* When set to zero by userspace, this is filled with the size of the
* data to be written at the data_ptr pointer. The kernel sets this
* value to a negative value to signal an error on a particular query
@@ -2233,21 +2242,26 @@ struct drm_i915_query_item {
*/
__s32 length;
- /*
+ /**
+ * @flags:
+ *
* When query_id == DRM_I915_QUERY_TOPOLOGY_INFO, must be 0.
*
* When query_id == DRM_I915_QUERY_PERF_CONFIG, must be one of the
- * following :
- * - DRM_I915_QUERY_PERF_CONFIG_LIST
- * - DRM_I915_QUERY_PERF_CONFIG_DATA_FOR_UUID
- * - DRM_I915_QUERY_PERF_CONFIG_FOR_UUID
+ * following:
+ *
+ * - DRM_I915_QUERY_PERF_CONFIG_LIST
+ * - DRM_I915_QUERY_PERF_CONFIG_DATA_FOR_UUID
+ * - DRM_I915_QUERY_PERF_CONFIG_FOR_UUID
*/
__u32 flags;
#define DRM_I915_QUERY_PERF_CONFIG_LIST 1
#define DRM_I915_QUERY_PERF_CONFIG_DATA_FOR_UUID 2
#define DRM_I915_QUERY_PERF_CONFIG_DATA_FOR_ID 3
- /*
+ /**
+ * @data_ptr:
+ *
* Data will be written at the location pointed by data_ptr when the
* value of length matches the length of the data to be written by the
* kernel.
@@ -2255,16 +2269,41 @@ struct drm_i915_query_item {
__u64 data_ptr;
};
+/**
+ * struct drm_i915_query - Supply an array of drm_i915_query_item for the kernel
+ * to fill out.
+ *
+ * Note that this is generally a two step process for each drm_i915_query_item
+ * in the array:
+ *
+ * 1. Call the DRM_IOCTL_I915_QUERY, giving it our array of drm_i915_query_item,
+ * with drm_i915_query_item.size set to zero. The kernel will then fill in
+ * the size, in bytes, which tells userspace how memory it needs to allocate
+ * for the blob(say for an array of properties).
+ *
+ * 2. Next we call DRM_IOCTL_I915_QUERY again, this time with the
+ * drm_i915_query_item.data_ptr equal to our newly allocated blob. Note that
+ * the i915_query_item.size should still be the same as what the kernel
+ * previously set. At this point the kernel can fill in the blob.
+ *
+ * Note that for some query items it can make sense for userspace to just pass
+ * in a buffer/blob equal to or larger than the required size. In this case only
+ * a single ioctl call is needed. For some smaller query items this can work
+ * quite well.
+ *
+ */
struct drm_i915_query {
+ /** @num_items: The number of elements in the @items_ptr array */
__u32 num_items;
- /*
- * Unused for now. Must be cleared to zero.
+ /**
+ * @flags: Unused for now. Must be cleared to zero.
*/
__u32 flags;
- /*
- * This points to an array of num_items drm_i915_query_item structures.
+ /**
+ * @items_ptr: This points to an array of num_items drm_i915_query_item
+ * structures.
*/
__u64 items_ptr;
};
--
2.26.3
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