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

[Daniel Vetter]

On Thu, Dec 22, 2016 at 08:36:08AM +0000, Chris Wilson wrote:
> 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/

Is that happening? I mean including some kernel-doc and all that fun?
-Daniel

> 
> 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 at chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: David Herrmann <dh.herrmann at gmail.com>
> Reviewed-by: Joonas Lahtinen <joonas.lahtinen at 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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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch