Re: [PATCH v2 1/3] hwmon: ltc2990: refactor value conversion

[Guenter Roeck <linux@roeck-us.net>]

On 11/18/2016 12:18 AM, Tom Levens wrote:
> Hi Guenter,
>
> On Thu, 17 Nov 2016, Guenter Roeck wrote:
>
>> On 11/17/2016 08:23 AM, Tom Levens wrote:
>>>  Hi Guenter,
>>>
>>>  Thanks for taking the time to review the patch.
>>>
>>>  On Thu, 17 Nov 2016, Guenter Roeck wrote:
>>>
>>> >  Hi Tom,
>>> > >  On 11/17/2016 04:10 AM, Tom Levens wrote:
>>> > >   Conversion from raw values to signed integers has been refactored > >   using
>>> > >   the macros in bitops.h.
>>> > > >  Please also mention that this fixes a bug in negative temperature >  conversions.
>>>
>>>  Yes, of course, I will include the information in v3.
>>>
>>> > > >   Signed-off-by: Tom Levens <tom.levens@cern.ch>
>>> > >   ---
>>> > >    drivers/hwmon/ltc2990.c |   27 ++++++++++-----------------
>>> > >    1 files changed, 10 insertions(+), 17 deletions(-)
>>> > > > >   diff --git a/drivers/hwmon/ltc2990.c b/drivers/hwmon/ltc2990.c
>>> > >   index 8f8fe05..0ec4102 100644
>>> > >   --- a/drivers/hwmon/ltc2990.c
>>> > >   +++ b/drivers/hwmon/ltc2990.c
>>> > >   @@ -9,8 +9,12 @@
>>> > >     * This driver assumes the chip is wired as a dual current monitor, > >     and
>>> > >     * reports the voltage drop across two series resistors. It also > >     reports
>>> > >     * the chip's internal temperature and Vcc power supply voltage.
>>> > >   + *
>>> > >   + * Value conversion refactored
>>> > >   + * by Tom Levens <tom.levens@cern.ch>
>>> > >  Kind of unusual to do that for minor changes like this. Imagine if >  everyone would do that.
>>> >  The commit log is what gives you credit.
>>>
>>>  Good point, thanks for the hint. I will remove it from v3.
>>>
>>> > >     */
>>> > > > >   +#include <linux/bitops.h>
>>> > >    #include <linux/err.h>
>>> > >    #include <linux/hwmon.h>
>>> > >    #include <linux/hwmon-sysfs.h>
>>> > >   @@ -34,19 +38,10 @@
>>> > >    #define LTC2990_CONTROL_MODE_CURRENT    0x06
>>> > >    #define LTC2990_CONTROL_MODE_VOLTAGE    0x07
>>> > > > >   -/* convert raw register value to sign-extended integer in 16-bit > >   range */
>>> > >   -static int ltc2990_voltage_to_int(int raw)
>>> > >   -{
>>> > >   -    if (raw & BIT(14))
>>> > >   -        return -(0x4000 - (raw & 0x3FFF)) << 2;
>>> > >   -    else
>>> > >   -        return (raw & 0x3FFF) << 2;
>>> > >   -}
>>> > >   -
>>> > >   /* Return the converted value from the given register in uV or mC */
>>> > >   -static int ltc2990_get_value(struct i2c_client *i2c, u8 reg, int > >   *result)
>>> > >   +static int ltc2990_get_value(struct i2c_client *i2c, u8 reg, s32 > >   *result)
>>> > >   {
>>> > >   -    int val;
>>> > >   +    s32 val;
>>> > >  Please just leave the variable type alone. it is also used for the >  return value
>>> >  from i2c_smbus_read_word_swapped(), which is an int, and changing it to >  s32 doesn't really make the code better.
>>>
>>>  According to i2c.h the return type for i2c_smbus_read_word_swapped() is
>>>  s32, which is why I modified it here. But it could be changed back if you
>>>  think it is better to leave it as an int.
>>>
>> Ah, ok. Good to know. Please leave it anyway, reason being that there is no real
>> reason to change it. Effectively those are just whitespace changes (unlike the rest,
>> which is part bug fix, part cleanup).
>>
>>> >  Can you send me a register map for the chip ? I would like to write a >  module test.
>>>
>>>  Here is an example register dump:
>>
>> I meant the output of i2cdump (something like "i2cdump -y -f <bus> <i2c-address> w").
>>
>
> The register map wraps at 0x0F, so I only sent you the first 16 bytes. But the fully expanded form is:
>
>      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
> 00: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> 10: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> 20: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> 30: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> 40: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> 50: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> 60: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> 70: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> 80: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> 90: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> a0: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> b0: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> c0: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> d0: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> e0: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00
> f0: 00 00 00 00 01 90 07 d0 2c cd 7d 80 7c 29 20 00

Sorry, I wasn't clear. The chip uses 16-bit registers, so the
"w" in the command would be important to report the entire
register content, not just the first 8 bit of each register.

Thanks,
Guenter

>
> Cheers,
>
>> Thanks,
>> Guenter
>>
>>>
>>>  00 00 00 00
>>>  01 90 07 d0
>>>  2c cd 7d 80
>>>  7c 29 20 00
>>>
>>>  The expected values in this case are:
>>>
>>>  in0_input     5000
>>>  in1_input    610
>>>  in2_input    3500
>>>  in3_input    -195
>>>  in4_input    -299
>>>  temp1_input     25000
>>>  temp2_input     125000
>>>  temp3_input    -40000
>>>  curr1_input    38840
>>>  curr2_input    -12428
>>>
>>>  Testing with lltc,mode set to <5>, <6> and <7> should give you all
>>>  measurements.
>>>
>>> >  Thanks,
>>> >  Guenter
>>>
>>>  Cheers,
>>>
>>
>>
>