linux-kernel - Re: [PATCH 3/6] hwmon: jc42: use bitops' sign

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Date:	Tue, 16 Dec 2014 08:17:25 +0100
From:	Martin Kepplinger <martink@...teo.de>
To:	Guenter Roeck <linux@...ck-us.net>
CC:	peterz@...radead.org, mingo@...nel.org, tytso@....edu,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] hwmon: jc42: use bitops' sign_extend16

Am 2014-12-15 um 22:29 schrieb Guenter Roeck:
> On Mon, Dec 15, 2014 at 05:18:34PM +0100, Martin Kepplinger wrote:
>> ---
> 
> Some description would be nice. Also, please consider adding
> relevant subsystem mailing lists and maintainers to your patches.
> 

I shouldn't have added the Signed-off-by line to some of them. Sorry.

The driver-patches are meant to be examples of what can be changed if
the sign_extend functions are added. I don't know if they are taken and
planned to post the driver patches (probably more) thereafter, and of
course to the relevant people.

>>  drivers/hwmon/jc42.c | 5 ++---
>>  1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/hwmon/jc42.c b/drivers/hwmon/jc42.c
>> index 388f8bc..335a2de 100644
>> --- a/drivers/hwmon/jc42.c
>> +++ b/drivers/hwmon/jc42.c
>> @@ -31,6 +31,7 @@
>>  #include <linux/hwmon-sysfs.h>
>>  #include <linux/err.h>
>>  #include <linux/mutex.h>
>> +#include <linux/bitops.h>
>>  
>>  /* Addresses to scan */
>>  static const unsigned short normal_i2c[] = {
>> @@ -215,9 +216,7 @@ static int jc42_temp_from_reg(s16 reg)
>>  {
>>  	reg &= 0x1fff;
>>  
> If I understand the code in sign_extend16 correctly, the above mask
> should no longer be necessary.

exactly. The mask would then be shifting. Thanks!

> 
> Thanks,
> Guenter
> 
>> -	/* sign extend register */
>> -	if (reg & 0x1000)
>> -		reg |= 0xf000;
>> +	reg = sign_extend16(reg, 12);
>>  
>>  	/* convert from 0.0625 to 0.001 resolution */
>>  	return reg * 125 / 2;
>> -- 
>> 2.1.3
>>
>> --
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