linux-kernel - Re: [PATCH] bitops: simplify get_count_order

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Date:   Thu, 28 May 2020 22:18:22 +0000
From:   Wei Yang <richard.weiyang@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Wei Yang <richard.weiyang@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        christian.brauner@...ntu.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bitops: simplify get_count_order_long()

On Wed, May 27, 2020 at 04:05:08PM -0700, Andrew Morton wrote:
>On Wed, 27 May 2020 22:45:42 +0000 Wei Yang <richard.weiyang@...il.com> wrote:
>
>> /* a tiny module only meant to test get_count_order/long */
>> unsigned int order_comb[][2] = {
>> 	{0x00000003,  2},
>> 	{0x00000004,  2},
>> 	{0x00001fff, 13},
>> 	{0x00002000, 13},
>> 	{0x50000000, 32},
>> 	{0x80000000, 32},
>> };
>> 
>> static int __init test_getorder_startup(void)
>> {
>> 	int i;
>> 
>> 	for (i = 0; i < ARRAY_SIZE(order_comb); i++) {
>> 		if (order_comb[i][1] != get_count_order(order_comb[i][0]))
>> 			pr_warn("get_count_order wrong for %lx\n",
>> 					order_comb[i][0]);
>> 	}
>> 
>> 	return 0;
>> }
>> 
>> Since I don't get a way to iterate all the possibilities, some random
>> combination is chosen. Is this one looks good?
>
>Looks good.
>
>You might want to add a less-negative number as well?  0x80030000. 
>Something that won't turn positive if it has 1 subtracted from it.

Thanks, this is a good suggestion.

-- 
Wei Yang
Help you, Help me