iio dummy device doesn't appear in /sys/bus/iio/devices/

["Franziska Näpelt" <franziska.naepelt@googlemail.com>]

Hi,

I=E2=80=99m just playing around with iio dummy drivers and couldn=E2=80=99=
t get it work with kernel 4.9 while everything was fine with=20
kernel 4.4.

Steps for kernel 4.4:
* edit Kconfig to create IIO_SIMPLE_DUMMY module
* build and install kernel
* edit /etc/modules to load iio_dummy
* after reboot there is an iio_dummy module loaded and the device =
appears in sysfs

Steps for kernel 4.9:
* edit Kconfig to create IIO_SW_DEVICE, IIO_SIMPLE_DUMMY, =
IIO_SIMPLE_DUMMY_BUFFER modules
* build and install kernel
* edit /etc/modules to load iio_dummy
* after reboot there is an iio_dummy module loaded but doesn=E2=80=99t =
appear in sysfs

Is there something wrong with the order, loading modules or do I miss =
some dependencies?

Thanks,
Franziska

Here are some more detailed information, as first kernel 4.4, then 4.9:

Linux raspberrypi-3 4.4.50-v7+ #1 SMP Fri Jun 2 00:19:42 CEST 2017 =
armv7l GNU/Linux
---
pi@raspberrypi-3:~/projects $ cat /etc/modules
# /etc/modules: kernel modules to load at boot time.
#
# This file contains the names of kernel modules that should be loaded
# at boot time, one per line. Lines beginning with "#" are ignored.

iio_dummy
---
pi@raspberrypi-3:~/projects/raspi-linux $ git diff =
drivers/staging/iio/Kconfig
diff --git a/drivers/staging/iio/Kconfig b/drivers/staging/iio/Kconfig
index 9d7f000..42d03a3 100644
--- a/drivers/staging/iio/Kconfig
+++ b/drivers/staging/iio/Kconfig
@@ -23,6 +23,7 @@ config IIO_DUMMY_EVGEN
=20
 config IIO_SIMPLE_DUMMY
        tristate "An example driver with no hardware requirements"
+          default y
        help
         Driver intended mainly as documentation for how to write
         a driver. May also be useful for testing userspace code
---
pi@raspberrypi-3:~/projects $ lsmod=20
Module                  Size  Used by
bnep                   10340  2=20
hci_uart               17943  1=20
btbcm                   5929  1 hci_uart
bluetooth             326067  22 bnep,btbcm,hci_uart
brcmfmac              186282  0=20
brcmutil                5661  1 brcmfmac
cfg80211              428833  1 brcmfmac
rfkill                 16018  4 cfg80211,bluetooth
snd_bcm2835            20447  0=20
snd_pcm                75890  1 snd_bcm2835
snd_timer              19288  1 snd_pcm
bcm2835_gpiomem         2976  0=20
snd                    51908  3 snd_bcm2835,snd_timer,snd_pcm
bcm2835_wdt             3225  0=20
uio_pdrv_genirq         3164  0=20
uio                     8000  1 uio_pdrv_genirq
iio_dummy               3072  0=20
industrialio           33826  1 iio_dummy
ipv6                  347563  32=20
---
pi@raspberrypi-3:/sys/bus/iio/devices/iio:device0 $ ll
insgesamt 0
drwxr-xr-x  3 root root    0 Jun  4 13:42 .
drwxr-xr-x 10 root root    0 Jun  4 13:42 ..
-r--r--r--  1 root root 4,0K Jun  4 13:42 dev
-rw-r--r--  1 root root 4,0K Jun  4 13:42 in_accel_x_calibbias
-rw-r--r--  1 root root 4,0K Jun  4 13:42 in_accel_x_calibscale
-rw-r--r--  1 root root 4,0K Jun  4 13:42 in_accel_x_raw
-rw-r--r--  1 root root 4,0K Jun  4 13:42 in_activity_running_input
-rw-r--r--  1 root root 4,0K Jun  4 13:42 in_activity_walking_input
-rw-r--r--  1 root root 4,0K Jun  4 13:42 in_sampling_frequency
-rw-r--r--  1 root root 4,0K Jun  4 13:42 in_steps_calibheight
-rw-r--r--  1 root root 4,0K Jun  4 13:42 in_steps_en
-rw-r--r--  1 root root 4,0K Jun  4 13:42 in_steps_input
-rw-r--r--  1 root root 4,0K Jun  4 13:42 in_voltage0_offset
-rw-r--r--  1 root root 4,0K Jun  4 13:42 in_voltage0_raw
-rw-r--r--  1 root root 4,0K Jun  4 13:42 in_voltage0_scale
-rw-r--r--  1 root root 4,0K Jun  4 13:42 in_voltage1-voltage2_raw
-rw-r--r--  1 root root 4,0K Jun  4 13:42 in_voltage3-voltage4_raw
-rw-r--r--  1 root root 4,0K Jun  4 13:42 in_voltage-voltage_scale
-r--r--r--  1 root root 4,0K Jun  4 13:42 name
-rw-r--r--  1 root root 4,0K Jun  4 13:42 out_voltage0_raw
drwxr-xr-x  2 root root    0 Jun  4 13:42 power
lrwxrwxrwx  1 root root    0 Jun  4 13:42 subsystem -> ../../bus/iio
-rw-r--r--  1 root root 4,0K Jun  4 13:42 uevent
=
--------------------------------------------------------------------------=
-----------------------------------------------
Linux raspberrypi-3 4.9.30-v7+ #1 SMP Sun Jun 4 21:07:31 CEST 2017 =
armv7l GNU/Linux
---
/etc/modules -> is the same
---=20
pi@raspberrypi-3:~/projects/raspi-linux $ git diff drivers/iio/Kconfig=20=

diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
index 6743b18..e804f63 100644
--- a/drivers/iio/Kconfig
+++ b/drivers/iio/Kconfig
@@ -49,6 +49,7 @@ config IIO_CONSUMERS_PER_TRIGGER
 config IIO_SW_DEVICE
        tristate "Enable software IIO device support"
        select IIO_CONFIGFS
+       default y
        help
         Provides IIO core support for software devices. A software
         device can be created via configfs or directly by a driver
---
pi@raspberrypi-3:~/projects/raspi-linux $ git diff =
drivers/iio/dummy/Kconfig
diff --git a/drivers/iio/dummy/Kconfig b/drivers/iio/dummy/Kconfig
index aa5824d..1eb7991 100644
--- a/drivers/iio/dummy/Kconfig
+++ b/drivers/iio/dummy/Kconfig
@@ -11,6 +11,7 @@ config IIO_DUMMY_EVGEN
 config IIO_SIMPLE_DUMMY
        tristate "An example driver with no hardware requirements"
        depends on IIO_SW_DEVICE
+          default y
        help
         Driver intended mainly as documentation for how to write
         a driver. May also be useful for testing userspace code
@@ -29,6 +30,7 @@ config IIO_SIMPLE_DUMMY_BUFFER
        select IIO_BUFFER
        select IIO_TRIGGER
        select IIO_KFIFO_BUF
+       default y
        help
          Add buffered data capture to the simple dummy driver.
---
pi@raspberrypi-3:~/projects/raspi-linux $ lsmod=20
Module                  Size  Used by
bnep                   12051  2=20
hci_uart               20020  1=20
btbcm                   7916  1 hci_uart
bluetooth             365473  22 hci_uart,bnep,btbcm
brcmfmac              222798  0=20
brcmutil                9092  1 brcmfmac
cfg80211              542989  1 brcmfmac
rfkill                 20832  4 bluetooth,cfg80211
snd_bcm2835            24427  0=20
snd_pcm                98565  1 snd_bcm2835
snd_timer              23904  1 snd_pcm
bcm2835_gpiomem         3940  0=20
snd                    70032  3 snd_timer,snd_bcm2835,snd_pcm
uio_pdrv_genirq         3923  0=20
fixed                   3285  0=20
uio                    10268  1 uio_pdrv_genirq
iio_dummy               4984  0=20
industrialio_sw_device     3691  1 iio_dummy
industrialio_configfs     1370  1 industrialio_sw_device
kfifo_buf               3668  1 iio_dummy
industrialio           62929  2 iio_dummy,kfifo_buf
ipv6                  408530  32=20
---
pi@raspberrypi-3:/sys/bus/iio/devices $ ll
insgesamt 0
drwxr-xr-x 2 root root 0 Jun  5 15:33 .
drwxr-xr-x 4 root root 0 Jun  5 15:33 ..