Message-Id: <WM!da6c96198354db7af9f225c848a09d5c6e064c622dbfcc6b4670fb1c3db17e0cc67ee54b34600a69dd8059b643e30774!@dg.advantech.com>
Date:   Tue, 31 Jan 2017 16:42:31 -0800
From:   "Ken.Lin" <ken.lin@...antech.com>
To:     Peter Rosin <peda@...ntia.se>,
        "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



> -----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/

Cheers,
Ken Lin

> Cheers,
> peda
> 
> > [ 3785.107740] Hardware name: Freescale i.MX6 Quad/DualLite (Device
> > Tree) [ 3785.114285] task: ed54ec00 task.stack: ee2bc000 [
> > 3785.118834] PC is at 0x0 [ 3785.121397] LR is at
> > iio_read_channel_info_avail+0x40/0x280
> > [ 3785.126992] pc : [<00000000>]    lr : [<c06fbc1c>]    psr: a0070013
> > [ 3785.126992] sp : ee2bdda8  ip : 00000000  fp : ee2bddf4 [
> > 3785.138490] r10: c0a53c74  r9 : ed79f000  r8 : ee8d1018 [
> > 3785.143733] r7 : 00001000  r6 : 00000fff  r5 : ee8b9a00  r4 :
> > ed79f000 [ 3785.150276] r3 : ee2bddc4  r2 : ee2bddbc  r1 : c0a86dcc
> > r0 : ee8d1000 [ 3785.156820] Flags: NzCv  IRQs on  FIQs on  Mode
> > SVC_32  ISA ARM  Segment none [ 3785.163971] Control: 10c5387d  Table:
> > 3cc3c04a  DAC: 00000051 [ 3785.169734] Process cat (pid: 1051, stack
> > limit = 0xee2bc210) [ 3785.175497] Stack: (0xee2bdda8 to 0xee2be000)
> > [ 3785.179880] dda0:                   ee2bddc0 00000002 c016d720 c016d394
> ed54ec00 00000000
> > [ 3785.188084] ddc0: 60070013 ed413780 00000001 edffd480 ee8b9a00
> > 00000fff 00001000 ee8d1018 [ 3785.196286] dde0: ed79f000 c0a53c74
> > ee2bde0c ee2bddf8 c0513c58 c06fbbe8 edffd480 edffd540 [ 3785.204488]
> > de00: ee2bde3c ee2bde10 c0293474 c0513c40 c02933e4 ee2bde60 00000001
> > ed413780 [ 3785.212688] de20: 00000001 ed413780 00000000 edffd480
> > ee2bde4c ee2bde40 c0291d00 c02933f0 [ 3785.220889] de40: ee2bde9c
> > ee2bde50 c024679c c0291ce0 edffd4b0 b6e37000 00020000 ee2bdf78 [
> > 3785.229089] de60: 00000000 00000000 ed54ec00 ed013200 00000817
> > c0a111fc edffd540 ed413780 [ 3785.237289] de80: b6e37000 00020000
> > 00020000 ee2bdf78 ee2bded4 ee2bdea0 c0292890 c0246604 [ 3785.245491]
> > dea0: c0117940 c016ba50 00000025 c0a111fc b6e37000 ed413780 ee2bdf78
> > 00020000 [ 3785.253691] dec0: ee2bc000 b6e37000 ee2bdf44 ee2bded8
> > c021d158 c0292770 c0117764 b6e36004 [ 3785.261893] dee0: c0f0d7c4
> > ee2bdfb0 b6f89228 00021008 ee2bdfac ee2bdf00 c0101374 c0117770 [
> > 3785.270093] df00: 00000000 00000000 ee2bc000 00000000 ee2bdf34
> > ee2bdf20 c016ba04 c0171080 [ 3785.278292] df20: 00000000 00020000
> > ed413780 b6e37000 00000000 ee2bdf78 ee2bdf74 ee2bdf48 [ 3785.286493]
> > df40: c021e7a0 c021d130 c023e300 c023e280 ee2bdf74 00000000 00000000
> > ed413780 [ 3785.294693] df60: ed413780 00020000 ee2bdfa4 ee2bdf78
> c021e870 c021e71c 00000000 00000000 [ 3785.302892] df80: 00020000
> 00020000 b6e37000 00000003 c0108084 00000000 00000000 ee2bdfa8 [
> 3785.311092] dfa0: c0107ee0 c021e838 00020000 00020000 00000003
> b6e37000 00020000 0001a2b4 [ 3785.319292] dfc0: 00020000 00020000
> b6e37000 00000003 7fffe000 00000000 00000000 00020000 [ 3785.327492]
> dfe0: 00000000 be98eb4c 0000c740 b6f1985c 60070010 00000003 00000000
> 00000000 [ 3785.335679] Backtrace:
> > [ 3785.338175] [<c06fbbdc>] (iio_read_channel_info_avail) from
> > [<c0513c58>] (dev_attr_show+0x24/0x50) [ 3785.347162]  r10:c0a53c74
> > r9:ed79f000 r8:ee8d1018 r7:00001000 r6:00000fff r5:ee8b9a00 [
> > 3785.355005]  r4:edffd480 [ 3785.357571] [<c0513c34>] (dev_attr_show)
> > from [<c0293474>] (sysfs_kf_seq_show+0x90/0x110) [ 3785.365764]
> > r5:edffd540 r4:edffd480 [ 3785.369365] [<c02933e4>]
> > (sysfs_kf_seq_show) from [<c0291d00>] (kernfs_seq_show+0x2c/0x30) [
> > 3785.377652]  r10:edffd480 r9:00000000 r8:ed413780 r7:00000001
> > r6:ed413780 r5:00000001 [ 3785.385498]  r4:ee2bde60 r3:c02933e4 [
> > 3785.389101] [<c0291cd4>] (kernfs_seq_show) from [<c024679c>]
> > (seq_read+0x1a4/0x4e0) [ 3785.396780] [<c02465f8>] (seq_read) from
> > [<c0292890>] (kernfs_fop_read+0x12c/0x1cc) [ 3785.404460]
> > r10:ee2bdf78 r9:00020000 r8:00020000 r7:b6e37000 r6:ed413780
> > r5:edffd540 [ 3785.412303]  r4:c0a111fc [ 3785.414862] [<c0292764>]
> > (kernfs_fop_read) from [<c021d158>] (__vfs_read+0x34/0x118) [
> > 3785.422627]  r10:b6e37000 r9:ee2bc000 r8:00020000 r7:ee2bdf78
> > r6:ed413780 r5:b6e37000 [ 3785.430470]  r4:c0a111fc [ 3785.433029]
> > [<c021d124>] (__vfs_read) from [<c021e7a0>] (vfs_read+0x90/0x11c) [
> > 3785.440185]  r8:ee2bdf78 r7:00000000 r6:b6e37000 r5:ed413780
> > r4:00020000 [ 3785.446909] [<c021e710>] (vfs_read) from [<c021e870>]
> > (SyS_read+0x44/0x90) [ 3785.453804]  r8:00020000 r7:ed413780
> > r6:ed413780 r5:00000000 r4:00000000 [ 3785.460537] [<c021e82c>]
> > (SyS_read) from [<c0107ee0>] (ret_fast_syscall+0x0/0x1c) [
> > 3785.468042]  r10:00000000 r8:c0108084 r7:00000003 r6:b6e37000
> > r5:00020000 r4:00020000 [ 3785.476238] Code: bad PC value [
> > 3785.490358] ---[ end trace 9c4938ccd0389004 ]---
> >
> > Thank you
> >
> > Cheers,
> > Ken Lin
> >
> 
> 
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