lkml.org 
[lkml]   [2011]   [Nov]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [lm-sensors] [PATCH] hwmon: (max1111) change sysfs interface to in[0-3]_input in millivolts
On Wed, Nov 9, 2011 at 8:51 PM, Jean Delvare <khali@linux-fr.org> wrote:
> On Wed, 9 Nov 2011 20:33:27 +0800, Eric Miao wrote:
>> On Wed, Nov 9, 2011 at 8:22 PM, Jean Delvare <khali@linux-fr.org> wrote:
>> > Hi Eric,
>> >
>> > On Wed,  9 Nov 2011 19:15:03 +0800, Eric Miao wrote:
>> >> This patch fixed the inconsistent max1111 sysfs interface as pointed
>> >> out by Jean Delvare:
>> >>
>> >>     It was pointed to me that the max1111 driver doesn't implement the
>> >>     standard sysfs interface for hwmon drivers (as described in
>> >>     Documentation/hwmon/sysfs-interface). It exports files adc[0-3]_in,
>> >>     which
>> >>     aren't part of the standard interface. Presumably these should be
>> >>     renamed to in[0-3]_input. Renaming them is probably not sufficient
>> >>     though, as I see no scaling done in the driver. As the MAX1111 chip has
>> >>     a documented full scale of 2.048V, I take it that the LSB of the ADC
>> >>     has a weight of 8 mV. Exporting raw register values to user-space is
>> >>     not OK.
>> >>
>> >> Reported-by: Jean Delvare <khali@linux-fr.org>
>> >> Signed-off-by: Eric Miao <eric.y.miao@gmail.com>
>> >> ---
>> >>  drivers/hwmon/max1111.c |   13 +++++++------
>> >>  1 files changed, 7 insertions(+), 6 deletions(-)
>> >>
>> >> diff --git a/drivers/hwmon/max1111.c b/drivers/hwmon/max1111.c
>> >> index c97b78e..0e9fcfd 100644
>> >> --- a/drivers/hwmon/max1111.c
>> >> +++ b/drivers/hwmon/max1111.c
>> >> @@ -106,11 +106,12 @@ static ssize_t show_adc(struct device *dev,
>> >>       if (ret < 0)
>> >>               return ret;
>> >>
>> >> -     return sprintf(buf, "%d\n", ret);
>> >> +     /* assume the reference voltage to be 2.048V */
>> >> +     return sprintf(buf, "%d\n", 2048 * 256 / ret);
>> >
>> > I bet you did not actually test your changes? ret == 0 would obviously
>> > crash the driver. The formula looks wrong anyway, should be 2048 *
>> > ret / 256. Or in short ret * 8, i.e. LSB weight of the ADC is 8 mV.
>> >
>>
>> Oops, shame to death.
>>
>> How about simply '2048 * ret / 256' to make it clear and leave it to
>> the compiler to optimize?
>
> I find the concept of LSB weight clear enough, but ultimately that's up
> to you, as long as the compiler actually optimizes it.

Sounds good, updated and resubmitted.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2011-11-09 14:05    [W:0.104 / U:0.008 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site