For testing, we want a reproducible PRNG, a plain linear congruent
generator is suitable for our very limited selftests.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/Kconfig | 5 +++++
drivers/gpu/drm/Makefile | 1 +
drivers/gpu/drm/lib/drm_rand.c | 51 ++++++++++++++++++++++++++++++++++++++++++
drivers/gpu/drm/lib/drm_rand.h | 9 ++++++++
4 files changed, 66 insertions(+)
create mode 100644 drivers/gpu/drm/lib/drm_rand.c
create mode 100644 drivers/gpu/drm/lib/drm_rand.h
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index fd341ab69c46..04d1d0a32c5c 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -48,10 +48,15 @@ config DRM_DEBUG_MM
If in doubt, say "N".
+config DRM_LIB_RAND
+ bool
+ default n
+
config DRM_DEBUG_MM_SELFTEST
tristate "kselftests for DRM range manager (struct drm_mm)"
depends on DRM
depends on DEBUG_KERNEL
+ select DRM_LIB_RAND
default n
help
This option provides a kernel module that can be used to test
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index c8aed3688b20..363eb1a23151 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-$(CONFIG_DRM_LIB_RAND) += lib/drm_rand.o
obj-$(CONFIG_DRM_DEBUG_MM_SELFTEST) += selftests/test-drm_mm.o
drm-$(CONFIG_COMPAT) += drm_ioc32.o
diff --git a/drivers/gpu/drm/lib/drm_rand.c b/drivers/gpu/drm/lib/drm_rand.c
new file mode 100644
index 000000000000..f203c47bb525
--- /dev/null
+++ b/drivers/gpu/drm/lib/drm_rand.c
@@ -0,0 +1,51 @@
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#include "drm_rand.h"
+
+u32 drm_lcg_random(u32 *state)
+{
+ u32 s = *state;
+
+#define rol(x, k) (((x) << (k)) | ((x) >> (32 - (k))))
+ s = (s ^ rol(s, 5) ^ rol(s, 24)) + 0x37798849;
+#undef rol
+
+ *state = s;
+ return s;
+}
+EXPORT_SYMBOL(drm_lcg_random);
+
+int *drm_random_reorder(int *order, int count, u32 *state)
+{
+ int n;
+
+ for (n = count-1; n > 1; n--) {
+ int r = drm_lcg_random(state) % (n + 1);
+ if (r != n) {
+ int tmp = order[n];
+ order[n] = order[r];
+ order[r] = tmp;
+ }
+ }
+
+ return order;
+}
+EXPORT_SYMBOL(drm_random_reorder);
+
+int *drm_random_order(int count, u32 *state)
+{
+ int *order;
+ int n;
+
+ order = kmalloc_array(count, sizeof(*order), GFP_TEMPORARY);
+ if (!order)
+ return order;
+
+ for (n = 0; n < count; n++)
+ order[n] = n;
+
+ return drm_random_reorder(order, count, state);
+}
+EXPORT_SYMBOL(drm_random_order);
diff --git a/drivers/gpu/drm/lib/drm_rand.h b/drivers/gpu/drm/lib/drm_rand.h
new file mode 100644
index 000000000000..a3f22d115aac
--- /dev/null
+++ b/drivers/gpu/drm/lib/drm_rand.h
@@ -0,0 +1,9 @@
+#ifndef __DRM_RAND_H__
+#define __DRM_RAND_H
+
+u32 drm_lcg_random(u32 *state);
+
+int *drm_random_reorder(int *order, int count, u32 *state);
+int *drm_random_order(int count, u32 *state);
+
+#endif /* __DRM_RAND_H__ */
--
2.11.0
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