Hi,

Since you have only one attribute, it is working for you.
There is a dereference error in *channels.

Check the attached diff, which will fix this.

Thanks,
Srinivas

On 07/09/2014 03:12 PM, Reyad Attiyat wrote:
> Hey Srinivas,
>
> I did look into the panic you sent. I wasn't sure exactly what caused
> the NULL pointer.
> I tested it with out applying the last rotation from north patch, so
> no hid usages are found, my device only has rotation_from_north, and
> hid_parse_report() would return -EINVAL.
> I added another check to make sure a iio channel were set up, and
> return -EINVAL if not, but couldn't think of anything else.
>
> Could you test this version with dynamic debugging and see if it is
> finding any hid usage attributes.
> Any ideas what could cause this? I think I'm handling errors properly
> by returning what parse_report returns (-EINVAL or -ENOMEM) in probe
>
> Thanks,
> Reyad Attiyat
>
> On Wed, Jul 9, 2014 at 2:45 PM, Srinivas Pandruvada
> <srinivas.pandruvada@linux.intel.com> wrote:
>> On 07/09/2014 12:30 PM, Reyad Attiyat wrote:
>>> This series of patches modifies magn-3d driver to handle the rotation
>>> from north usage. This is done by scanning the report and then building
>>> the iio arrays (vals and channels) dynamically.
>>>
>>> Changes from V4
>>> I use the address field of struct iio_chan_spec to hold the array index
>>> of the usage attribute. The scan_index field is generated when creating
>>> an iio channel.
>>>
>>> Reyad Attiyat (4):
>>>     iio: Documentation: Add documentation for rotation from north sensor
>>>       usage attributes
>>>     iio: types: Added support for rotation from north usage attributes
>>>     iio: hid-sensor-magn-3d: Scan for usage attributes before setting up
>>>       iio channels
>>>     iio: hid-sensor-magn-3d: Add support for rotation from north
>>>
>>>    Documentation/ABI/testing/sysfs-bus-iio       |  82 +++++++++++
>>>    drivers/iio/industrialio-core.c               |   4 +
>>>    drivers/iio/magnetometer/hid-sensor-magn-3d.c | 199
>>> ++++++++++++++++++++------
>>>    include/linux/iio/types.h                     |   4 +
>>>    4 files changed, 245 insertions(+), 44 deletions(-)
>>>
>> Did you get chance to look at the cause of panic?
>>
>> Thanks,
>> Srinivas