Hello Peter,
>> Get square root of a 64-bit digit on 32bit platforms. CSR SiRFSoC
>> touchscreen driver needs it.
> maybe the code could be #MACRO()'d to avoid duplication
Do you mean to define int64_sqrt() directly as int_sqrt() on a 64 bit platform where sizeof(long) == sizeof(long long)?
Yibo
________________________________________
From: Peter Meerwald [pmeerw@xxxxxxxxxx]
Sent: Monday, June 23, 2014 5:52 PM
To: Barry Song
Cc: dmitry.torokhov@xxxxxxxxx; dtor@xxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx; linux-input@xxxxxxxxxxxxxxx; DL-SHA-WorkGroupLinux; Yibo Cai; Barry Song
Subject: Re: [PATCH 1/2] lib: int_sqrt: add int64_sqrt routine
> Get square root of a 64-bit digit on 32bit platforms. CSR SiRFSoC
> touchscreen driver needs it.
maybe the code could be #MACRO()'d to avoid duplication
see comment below
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index 4c52907..6e63081 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -418,6 +418,7 @@ struct pid;
> extern struct pid *session_of_pgrp(struct pid *pgrp);
>
> unsigned long int_sqrt(unsigned long);
> +unsigned long long int64_sqrt(unsigned long long);
>
> extern void bust_spinlocks(int yes);
> extern int oops_in_progress; /* If set, an oops, panic(), BUG() or die() is in progress */
> diff --git a/lib/int_sqrt.c b/lib/int_sqrt.c
> index 1ef4cc3..2aa9fcc 100644
> --- a/lib/int_sqrt.c
> +++ b/lib/int_sqrt.c
> @@ -36,3 +36,30 @@ unsigned long int_sqrt(unsigned long x)
> return y;
> }
> EXPORT_SYMBOL(int_sqrt);
> +
> +/*
> + * Square root of a 64-bit digit.
> + * Same as int_sqrt on 64-bit platforms where "long" equals "long long"
> + */
> +unsigned long long int64_sqrt(unsigned long long x)
> +{
> + unsigned long long m = 0, y = 0, b = 0;
initialization for b, m not needed
the original int_sqrt() code correctly skips initialization
> +
> + if (x <= 1)
> + return x;
> +
> + m = 1ULL << (BITS_PER_LONG_LONG - 2);
> + while (m != 0) {
> + b = y + m;
> + y >>= 1;
> +
> + if (x >= b) {
> + x -= b;
> + y += m;
> + }
> + m >>= 2;
> + }
> +
> + return y;
> +}
> +EXPORT_SYMBOL(int64_sqrt);
>
--
Peter Meerwald
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