Please add overlay for MCP3422/3/4 ADCs

[soosp]

Describe the bug
There is no overlay for these chips but they are supported by linux kernel.
The command
echo mcp3422 0x68 > /sys/class/i2c-adapter/i2c-1/new_device
loads the proper kernel module (mcp3422)

To reproduce
ls /boot/overlays/mcp34*
ls: cannot access '/boot/overlays/mcp34*': No such file or directory

Expected behaviour
Overlay available.

Actual behaviour
Overlay is missing.

System

• Which model of Raspberry Pi?
  Raspberry Pi 3 model B

• Which OS and version (cat /etc/rpi-issue)?
  Raspberry Pi reference 2018-11-13
  Generated using pi-gen, https://github.com/RPi-Distro/pi-gen, 7e0c786c641ba15990b5662f092c106beed40c9f, stage2

• Which firmware version (vcgencmd version)?
  Nov 4 2018 16:31:07
  Copyright (c) 2012 Broadcom
  version ed5baf9520a3c4ca82ba38594b898f0c0446da66 (clean) (release)

• Which kernel version (uname -a)?
  Linux pi3 4.14.79-v7+ USB-Harddrive gets fully powered down #1159 SMP Sun Nov 4 17:50:20 GMT 2018 armv7l GNU/Linux

Logs
If applicable, add the relevant output from dmesg or similar.

Additional context
Add any other relevant context for the problem.

[pelwell]

There's a trial mcp342x overlay here. The README will say:

Name:   mcp342x
Info:   Overlay for activation of Microchip MCP3421-3428 ADCs over I2C
Load:   dtoverlay=mcp342x,<param>=<val>
Params: addr                    I2C bus address of device, for devices with
                                addresses that are configurable, e.g. by
                                hardware links (default=0x68)
        mcp3421                 The device is an MCP3421
        mcp3422                 The device is an MCP3422
        mcp3423                 The device is an MCP3423
        mcp3424                 The device is an MCP3424
        mcp3425                 The device is an MCP3425
        mcp3426                 The device is an MCP3426
        mcp3427                 The device is an MCP3427
        mcp3428                 The device is an MCP3428

[soosp]

Thanks for the quick response! It works well.

Here is my config:

/boot/config.txt:
# Enable MCP3422 ADC
dtoverlay=mcp342x,addr=0x68,mcp3422

The results:

lsmod | grep mcp342*
mcp3422                16384  0
industrialio           73728  1 mcp3422

ls -1 /sys/class/i2c-adapter/i2c-1/1-0068/iio\:device0/
dev
in_voltage0_raw
in_voltage0_scale
in_voltage1_raw
in_voltage1_scale
in_voltage_sampling_frequency
in_voltage_scale_available
name
of_node
power
sampling_frequency_available
subsystem
uevent

cat /sys/class/i2c-adapter/i2c-1/1-0068/iio\:device0/in_voltage0_raw
287

[pelwell]

Thanks - that's now merged, and will be in future releases.