linux-kernel - Re: kernel 4.10-rcx iio helper question

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Date:   Wed, 01 Feb 2017 17:25:08 +0000
From:   Jonathan Cameron <jic23@...23.retrosnub.co.uk>
To:     Peter Rosin <peda@...ntia.se>, "Ken.Lin" <ken.lin@...antech.com>,
        "jic23@...nel.org" <jic23@...nel.org>
CC:     "knaack.h@....de" <knaack.h@....de>,
        "pmeerw@...erw.net" <pmeerw@...erw.net>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Akshay Bhat <akshay.bhat@...esys.com>,
        "Peter.Stretz" <peter.stretz@...antech.com>,
        "Peter.Chiang" <peter.chiang@...antech.com>
Subject: Re: kernel 4.10-rcx iio helper question



On 1 February 2017 05:50:12 GMT+00:00, Peter Rosin <peda@...ntia.se> wrote:
>On 2017-02-01 01:42, Ken.Lin wrote:
>> 
>> 
>>> -----Original Message-----
>>> From: Peter Rosin [mailto:peda@...ntia.se]
>>> Sent: Tuesday, January 31, 2017 1:10 PM
>>> To: Ken.Lin; jic23@...nel.org
>>> Cc: knaack.h@....de; pmeerw@...erw.net; linux-iio@...r.kernel.org;
>linux-
>>> kernel@...r.kernel.org; Akshay Bhat; Peter.Stretz; Peter.Chiang
>>> Subject: Re: kernel 4.10-rcx iio helper question
>>>
>>> On 2017-01-31 19:19, Ken.Lin wrote:
>>>> Hi,
>>>>
>>>> I find the latest kernel introduces new iio sys attributes.
>>>> https://patchwork.kernel.org/patch/9391771/
>>>> https://patchwork.kernel.org/patch/9391259/
>>>>
>>>> Is there anyone has some ideas about how the new iio sys attribute
>-
>>> in_pressure_scale_available works?
>>>> I'm not sure if it's the regression issue or it's just the usage
>issue or something
>>> when I tried to read in_pressure_scale_available attribute.
>>>
>>>> # cat /sys/bus/iio/devices/iio\:device1/in_pressure_scale_available
>>>> Segmentation fault
>>>
>>> What driver is providing iio:device1?
>>>
>>>> [ 3785.077014] Unable to handle kernel NULL pointer dereference at
>>>> virtual address 00000000 [ 3785.085138] pgd = ecc3c000 [
>3785.087929]
>>>> [00000000] *pgd=87f91831 [ 3785.091563] Internal error: Oops:
>80000007
>>>> [#1] SMP ARM [ 3785.096806] Modules linked in:
>>>> [ 3785.099892] CPU: 1 PID: 1051 Comm: cat Not tainted
>>>> 4.10.0-rc5-00009-gffd8858-dirty #3
>>>
>>> Looks like you have a couple of local changes? What are those?
>>>
>> 
>> I didn't make any changes to the iio drivers locally and MPL3115A2
>pressure/temperature sensor driver (drivers/iio/pressure/mpl3115.c) is
>the driver which provides iio:device1.
>> 
>>> My WAG is that you added the IIO_CHAN_INFO_SCALE bit to one of the
>>> .info_mask_*_available fields in the channel spec but failed to
>provide a
>>> .read_avail operation in the driver. Am I close?
>>>
>> 
>> I could read iio:device0/in_accel_scale and
>device0/in_accel_available, which are provided by NXP 3-axis
>accelerometers driver (drivers/iio/accel/mma8452.c).
>> The attribute iio:/device1/in_pressure_scale is missing unless I
>reverted the commits.
>> https://patchwork.kernel.org/patch/9391771/
>> https://patchwork.kernel.org/patch/9391259/
>
>Whoops, sorry for suggesting you did something wrong...
>
>Can you try this patch?
Gah. My eyes passed straight over that.

Thanks Ken, nice regression report and thank peda for the fix.

Phew, single driver bug rather than a general regression!

Jonathan
>
>Cheers,
>peda
>
>diff --git a/drivers/iio/pressure/mpl115.c
>b/drivers/iio/pressure/mpl115.c
>index 73f2f0c46e62..8f2bce213248 100644
>--- a/drivers/iio/pressure/mpl115.c
>+++ b/drivers/iio/pressure/mpl115.c
>@@ -137,6 +137,7 @@ static const struct iio_chan_spec mpl115_channels[]
>= {
> 	{
> 		.type = IIO_TEMP,
> 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
>+		.info_mask_shared_by_type =
> 			BIT(IIO_CHAN_INFO_OFFSET) | BIT(IIO_CHAN_INFO_SCALE),
> 	},
> };
>diff --git a/drivers/iio/pressure/mpl3115.c
>b/drivers/iio/pressure/mpl3115.c
>index cc3f84139157..525644a7442d 100644
>--- a/drivers/iio/pressure/mpl3115.c
>+++ b/drivers/iio/pressure/mpl3115.c
>@@ -190,7 +190,7 @@ static const struct iio_chan_spec
>mpl3115_channels[] = {
> 	{
> 		.type = IIO_PRESSURE,
> 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
>-			BIT(IIO_CHAN_INFO_SCALE),
>+		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
> 		.scan_index = 0,
> 		.scan_type = {
> 			.sign = 'u',
>@@ -203,7 +203,7 @@ static const struct iio_chan_spec
>mpl3115_channels[] = {
> 	{
> 		.type = IIO_TEMP,
> 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
>-			BIT(IIO_CHAN_INFO_SCALE),
>+		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
> 		.scan_index = 1,
> 		.scan_type = {
> 			.sign = 's',

-- 
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