I2C Slave questions on i.MX7 board

First this is not a Pi, it's a different SBC (i.MX7).

I've been assigned an interesting task, I need to do I2C Multi-Master where we're transferring a status request and commands between two I2C master. I've not worked with I2C so I don't know how to proceed.

I've been doing a lot of searching and I've found that a device can be an I2C master and a slave (good). The problem I have is that if my daemon (master A) is running I need to use the i2c-x device to be the master and that's okay. I can send a request (write to the slave B). But in order for the other master (B) to send updates randomly to the daemon I need to have the daemon controller (A) also be a slave. But the slave device, like the eeprom sample from the 2015 I2C slave device, is in the sysfs. That makes coding in the daemon a bit messy as I don't get a software interrupt (there is no change on file change). Is there some other way to get the data from the I2C subsystems?

Device A = Master A and Slave A
Device B = Master B and Slave B

Master A issues commands (I2C Write) -> Slave B (Device B)
Master B issues updates (I2C Write) -> Slave A (Device A)

And I have given consideration of having my daemon poll the other master for the status. I just want to cover my bases.

Master A issues commands (I2C Write) -> Slave B
Master A issues poll for status (I2C Read) <- Slave B

Any comments or suggest?

For multi-master, you need a form of bus arbitration.

One way would be unique bus signalling.

Another way would be to use HW signalling.

Originally Posted by rtmistler For multi-master, you need a form of bus arbitration. One way would be unique bus signalling. Another way would be to use HW signalling.

Not going to play with the bus signaling and I can't get an additional hardware signal. But I found a link on using the i2c-stub and a suggestion that one of the ioctl calls will work. So I'll give that a try. I'm not too thrilled with the sysfs interface but I can live with it if I can get something that says 'come and get it'.

https://eraretuya.github.io/2016/12/...tub-in-action/

This is the i2c-stub link. The link that mentioned may have been a different link. Hopefully that will work. Otherwise I'll resort to treachery and drop a cheap Arduino Uno Pro and translate the I2C to plain serial. ;-) Not sure how the main Engineer will like that but he's changing the interface after the demo date and won't tell me what he has in mind.