linux-kernel - Re: [PATCHv6 1/5] lib/genalloc.c: Add power aligned algorithm

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Date:	Fri, 8 Aug 2014 15:36:35 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Laura Abbott <lauraa@...eaurora.org>
Cc:	Will Deacon <will.deacon@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Russell King <linux@....linux.org.uk>,
	David Riley <davidriley@...omium.org>,
	linux-arm-kernel@...ts.infradead.org,
	Ritesh Harjain <ritesh.harjani@...il.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Thierry Reding <thierry.reding@...il.com>,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCHv6 1/5] lib/genalloc.c: Add power aligned algorithm

On Fri,  8 Aug 2014 13:23:13 -0700 Laura Abbott <lauraa@...eaurora.org> wrote:

> 
> One of the more common algorithms used for allocation
> is to align the start address of the allocation to
> the order of size requested. Add this as an algorithm
> option for genalloc.
> 
> --- a/lib/genalloc.c
> +++ b/lib/genalloc.c
> @@ -481,6 +481,27 @@ unsigned long gen_pool_first_fit(unsigned long *map, unsigned long size,
>  EXPORT_SYMBOL(gen_pool_first_fit);
>  
>  /**
> + * gen_pool_first_fit_order_align - find the first available region
> + * of memory matching the size requirement. The region will be aligned
> + * to the order of the size specified.
> + * @map: The address to base the search on
> + * @size: The bitmap size in bits
> + * @start: The bitnumber to start searching at
> + * @nr: The number of zeroed bits we're looking for
> + * @data: additional data - unused

`data' is used.

> + */
> +unsigned long gen_pool_first_fit_order_align(unsigned long *map,
> +		unsigned long size, unsigned long start,
> +		unsigned int nr, void *data)
> +{
> +	unsigned long order = (unsigned long) data;

Why pass a void*?  Why not pass "unsigned order;"?

> +	unsigned long align_mask = (1 << get_order(nr << order)) - 1;
> +
> +	return bitmap_find_next_zero_area(map, size, start, nr, align_mask);
> +}
> +EXPORT_SYMBOL(gen_pool_first_fit_order_align);
> +
> +/**
>   * gen_pool_best_fit - find the best fitting region of memory
>   * macthing the size requirement (no alignment constraint)
>   * @map: The address to base the search on

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