Add an overlay for the Ti ADS1015 A/D

[eriksejr]

I created this for a project I did recently. This overlay works with the existing ads1015 hwmon kernel driver. I tried to make it as flexible as possible, making most options configurable via config.txt.

I would have liked to target the alias "i2c_arm" rather then the exact path with the memory address but I could not get the enabling/disabling of fragments to work properly as I could not seem to target a previous fragment with a later one. This is my first device tree overlay so there may be a way to do that which I am not aware of.

I created a README.md in my repo for it: https://github.com/eriksejr/rpi_ads1015

Feedback is welcome.

[pelwell]

That's a good attempt, but you'd be better off doing something like this. It uses the exported symbol i2c_arm which is mapped to the correct i2c interface for the model in use. Fragment 0 uses a target property with a phandle reference (<&i2c_arm>), while the others use target-path with an alias as the start of the path and append the name of the added node (i2c_arm/ads1015). You could use the target-path + alias format for fragment 0, but I prefer to use the more common format where possible.

Note that target-path = "alias/subnode"; requires very recent firmware - May 31st 2016 is the first compatible release, available using rpi-update. Prior to that you could only use target-path = "/absolute/path"; or target-path = "alias";.

If your channel numbers are arbitrary then I think it would be less confusing to either make the default numbers match your virtual channel names, i.e. 1-4, or use letters for your virtual channels.

In order to be accepted you will also need to add your overlay to the Makefile and README - observe the strict formatting (80 columns, no TABs) and alphabetical order rules.

[eriksejr]

Phil,
Thank you for the help & feedback. I have made all the changes you suggested and updated the Makefile/README. I upgraded my Pi 3 Rev B to the latest firmware as of tonight (kernel 4.4.12) and re-compiled it including the ads1015 kernel module along with all the changes.

[pelwell]

Add another blank line here.

[pelwell]

Address the comments above, squash the commits down to one (use git rebase -i) and update the PR (git push -f), then I'll merge it.

[eriksejr]

Having problems squashing this, when I caught up my fork there ended up being a few hundred commits between my first commit and my later commits. I'm just going to close this and re-open it with everything as one big commit