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That's not technically true - you can probe for I2C devices by only sending a START, an address, waiting for the client device to ACK (or not), and then sending a STOP. I don't think the linux kernel driver allows us to do this, but I've implemented this on some microcontrollers with lower-level control over the I2C hardware. It worked on all clients I tried it on.

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You can install i2c-tools and run i2cdetect from userspace.

https://learn.adafruit.com/scanning-i2c-addresses/raspberry-...

"Warning This program can confuse your I2C bus, cause data loss and worse!"

This is true. As stated elsewhere, sending START conditions to random I2C devices may confuse certain parts. It may also interrupt a driver that's already talking to a part on the bus. But in my lifetime working with I2C, I've never seen a part just go haywire because you scanned it this way.

Indeed, I’ve also done the same. It’s frustrating how Linux doesn’t allow this.

Part of me wonders if all devices actually handle a STOP before the first data byte correctly — without side effects…

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