[PATCH v4 05/38] drm: Add a simple generator of random permutations

Chris Wilson
2016-12-22T08:36:08Z

When testing, we want a random but yet reproducible order in which to
process elements. Here we create an array which is a random (using the
Tausworthe PRNG) permutation of the order in which to execute.

Note these are simple helpers intended to be merged upstream in lib/

v2: Tidier code by David Herrmann
v3: Add reminder that this code is intended to be temporary, with at
least the bulk of the prandom changes going to lib/

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: David Herrmann <dh.herrmann@gmail.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
---
drivers/gpu/drm/Kconfig | 4 ++++
drivers/gpu/drm/Makefile | 1 +
drivers/gpu/drm/lib/drm_random.c | 41 ++++++++++++++++++++++++++++++++++++++++
drivers/gpu/drm/lib/drm_random.h | 25 ++++++++++++++++++++++++
4 files changed, 71 insertions(+)
create mode 100644 drivers/gpu/drm/lib/drm_random.c
create mode 100644 drivers/gpu/drm/lib/drm_random.h

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index ebfe8404c25f..45a1c7468e88 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -321,3 +321,7 @@ config DRM_SAVAGE
chipset. If M is selected the module will be called savage.

endif # DRM_LEGACY
+
+config DRM_LIB_RANDOM
+ bool
+ default n
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index b9ae4280de9d..6bb416360ae4 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -18,6 +18,7 @@ drm-y := drm_auth.o drm_bufs.o drm_cache.o \
drm_plane.o drm_color_mgmt.o drm_print.o \
drm_dumb_buffers.o drm_mode_config.o

+drm-$(CONFIG_DRM_LIB_RANDOM) += lib/drm_random.o
drm-$(CONFIG_COMPAT) += drm_ioc32.o
drm-$(CONFIG_DRM_GEM_CMA_HELPER) += drm_gem_cma_helper.o
drm-$(CONFIG_PCI) += ati_pcigart.o
diff --git a/drivers/gpu/drm/lib/drm_random.c b/drivers/gpu/drm/lib/drm_random.c
new file mode 100644
index 000000000000..7b12a68c3b54
--- /dev/null
+++ b/drivers/gpu/drm/lib/drm_random.c
@@ -0,0 +1,41 @@
+#include <linux/bitops.h>
+#include <linux/kernel.h>
+#include <linux/random.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#include "drm_random.h"
+
+static inline u32 drm_prandom_u32_max_state(u32 ep_ro, struct rnd_state *state)
+{
+ return upper_32_bits((u64)prandom_u32_state(state) * ep_ro);
+}
+
+void drm_random_reorder(unsigned int *order, unsigned int count,
+ struct rnd_state *state)
+{
+ unsigned int i, j;
+
+ for (i = 0; i < count; ++i) {
+ BUILD_BUG_ON(sizeof(unsigned int) > sizeof(u32));
+ j = drm_prandom_u32_max_state(count, state);
+ swap(order[i], order[j]);
+ }
+}
+EXPORT_SYMBOL(drm_random_reorder);
+
+unsigned int *drm_random_order(unsigned int count, struct rnd_state *state)
+{
+ unsigned int *order, i;
+
+ order = kmalloc_array(count, sizeof(*order), GFP_TEMPORARY);
+ if (!order)
+ return order;
+
+ for (i = 0; i < count; i++)
+ order[i] = i;
+
+ drm_random_reorder(order, count, state);
+ return order;
+}
+EXPORT_SYMBOL(drm_random_order);
diff --git a/drivers/gpu/drm/lib/drm_random.h b/drivers/gpu/drm/lib/drm_random.h
new file mode 100644
index 000000000000..a78644bea7f9
--- /dev/null
+++ b/drivers/gpu/drm/lib/drm_random.h
@@ -0,0 +1,25 @@
+#ifndef __DRM_RANDOM_H__
+#define __DRM_RANDOM_H__
+
+/* This is a temporary home for a couple of utility functions that should
+ * be transposed to lib/ at the earliest convenience.
+ */
+
+#include <linux/random.h>
+
+#define DRM_RND_STATE_INITIALIZER(seed__) ({ \
+ struct rnd_state state__; \
+ prandom_seed_state(&state__, (seed__)); \
+ state__; \
+})
+
+#define DRM_RND_STATE(name__, seed__) \
+ struct rnd_state name__ = DRM_RND_STATE_INITIALIZER(seed__)
+
+unsigned int *drm_random_order(unsigned int count,
+ struct rnd_state *state);
+void drm_random_reorder(unsigned int *order,
+ unsigned int count,
+ struct rnd_state *state);
+
+#endif /* !__DRM_RANDOM_H__ */
--
2.11.0

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