Mesa (staging/22.1): util/draw: handle draw_count=0 when reading indirect parameters

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Module: Mesa
Branch: staging/22.1
Commit: 9d020c5b524d92073d17586f767112dea98edc1d
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=9d020c5b524d92073d17586f767112dea98edc1d

Author: Mike Blumenkrantz <michael.blumenkrantz at gmail.com>
Date:   Tue Apr 19 16:06:44 2022 -0400

util/draw: handle draw_count=0 when reading indirect parameters

Fixes: 3eb99323172 ("aux/draw: add a util function for reading back indirect draw params")

Reviewed-by: Marek Olšák <marek.olsak at amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15963>
(cherry picked from commit 07437fa3bdd88a51c497aeaa7ee4dce8c2724579)

---

 .pick_status.json                   | 2 +-
 src/gallium/auxiliary/util/u_draw.c | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/.pick_status.json b/.pick_status.json
index 70a41736f3e..98fc5ff02da 100644
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -346,7 +346,7 @@
         "description": "util/draw: handle draw_count=0 when reading indirect parameters",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": "3eb99323172902d34c80782aaa2d110567749cd9"
     },
diff --git a/src/gallium/auxiliary/util/u_draw.c b/src/gallium/auxiliary/util/u_draw.c
index 70721586738..273724f2a0a 100644
--- a/src/gallium/auxiliary/util/u_draw.c
+++ b/src/gallium/auxiliary/util/u_draw.c
@@ -154,6 +154,10 @@ util_draw_indirect_read(struct pipe_context *pipe,
          draw_count = dc_param[0];
       pipe_buffer_unmap(pipe, dc_transfer);
    }
+   if (!draw_count) {
+      *num_draws = draw_count;
+      return NULL;
+   }
    draws = malloc(sizeof(struct u_indirect_params) * draw_count);
    if (!draws)
       return NULL;