gallium: Add PIPE_COMPUTE_CAP_MAX_MEM_ALLOC_SIZE v2

v2:
  - Add comment in screen.rst
  - Report OpenCL required minimum for r600g

src/gallium/docs/source/screen.rst

@@ -239,6 +239,8 @@ pipe_screen::get_compute_param.
   resource.  Value type: ``uint64_t``.
 * ``PIPE_COMPUTE_CAP_MAX_INPUT_SIZE``: Maximum size of the INPUT
   resource.  Value type: ``uint64_t``.
+* ``PIPE_COMPUTE_CAP_MAX_MEM_ALLOC_SIZE``: Maximum size of a memory object
+  allocation in bytes.  Value type: ``uint64_t``.
 
 .. _pipe_bind:
 

src/gallium/drivers/r600/r600_pipe.c

@@ -667,6 +667,22 @@ static int r600_get_compute_param(struct pipe_screen *screen,
 		}
 		return sizeof(uint64_t);
 
+	case PIPE_COMPUTE_CAP_MAX_MEM_ALLOC_SIZE:
+		if (ret) {
+			uint64_t max_global_size;
+			uint64_t * max_mem_alloc_size = ret;
+			r600_get_compute_param(screen,
+					PIPE_COMPUTE_CAP_MAX_GLOBAL_SIZE,
+					&max_global_size);
+			/* OpenCL requres this value be at least
+			 * max(MAX_GLOBAL_SIZE / 4, 128 * 1024 *1024)
+			 * I'm really not sure what value to report here, but
+			 * MAX_GLOBAL_SIZE / 4 seems resonable.
+			 */
+			*max_mem_alloc_size = max_global_size / 4;
+		}
+		return sizeof(uint64_t);
+
 	default:
 		fprintf(stderr, "unknown PIPE_COMPUTE_CAP %d\n", param);
 		return 0;

src/gallium/include/pipe/p_defines.h

@@ -557,7 +557,8 @@ enum pipe_compute_cap
    PIPE_COMPUTE_CAP_MAX_GLOBAL_SIZE,
    PIPE_COMPUTE_CAP_MAX_LOCAL_SIZE,
    PIPE_COMPUTE_CAP_MAX_PRIVATE_SIZE,
-   PIPE_COMPUTE_CAP_MAX_INPUT_SIZE
+   PIPE_COMPUTE_CAP_MAX_INPUT_SIZE,
+   PIPE_COMPUTE_CAP_MAX_MEM_ALLOC_SIZE
 };
 
 /**