Please add MCP23008 I2C I/O extender overlay

[soosp]

Describe the bug
There is an overlay for MCP23017 but there is no one for MCP23008
The kernel driver (pinctrl_mcp23s08) is present and properly loaded by the following command:
echo mcp23008 0x20 > /sys/class/i2c-adapter/i2c-1/new_device

To reproduce
ls /boot/overlays/mcp23*
/boot/overlays/mcp23017.dtbo /boot/overlays/mcp23s17.dtbo

Expected behaviour
The prsence of the overlay.

Actual behaviour
Missing overlay

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]

This modified mcp23017 overlay accepts an extra parameter - mcp23008 - that should make it compatible with the MCP23008. Please download it, copy it to /boot/overlays (you'll need to sudo cp mcp23017.dtbo /boot/overlays...), then edit your config.txt to include the new parameter, e.g.:

dtoverlay=mcp23017,mcp23008,addr=0x20,gpiopin=4

That can become the new mcp23017 overlay if it works for you.

[soosp]

Thank you for quick response!
I made a quick test, and it works.

My /boot/config.txt entry:

# Enable MCP23008 I/O expander
dtoverlay=mcp23017,mcp23008,addr=0x20

The result:

lsmod | grep mcp23
pinctrl_mcp23s08       24576  8

for i in `seq 504 511`; do
        echo $i > /sys/class/gpio/export
        echo out > /sys/class/gpio/gpio$i/direction
done

ls -1 /sys/class/gpio/
export
gpio504
gpio505
gpio506
gpio507
gpio508
gpio509
gpio510
gpio511
gpiochip0
gpiochip100
gpiochip128
gpiochip504
unexport

I tested some gpios to toggle relays and it worked for me.

[pelwell]

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