Re: [PATCH 0/2] i2c-dev: Don't let userspace block adapter

[Lars-Peter Clausen]

On 07/06/2016 04:57 AM, Viresh Kumar wrote:
> Hi Wolfram/Jean,
> 
> I am part of the kernel team for Google's projectara [1], where we are
> building a module smart phone.
> 
> This series tries to fix one of the problems we hit on our system as we
> are required to hotplug pretty much every thing on the phone and so this
> fixes hotplug issues with i2c-dev.
> 
> As described in the second patch, the current implementation of i2c-dev
> file operations doesn't let the modules (hardware attached to the phone)
> eject from the phone as the cleanup path for the module hasn't finished
> yet (i2c adapter not removed).
> 
> We can't let the userspace block the kernel devices forever in such
> cases.
> 
> I was able to test them on the ARA phone with kernel 3.10 only and not
> mainline.

This sounds like you want hot-unplug. This is currently not support by the
I2C framework for adapters. A better approach compared to this series might
be to implement full hot-unplug support for I2C adapters. This will probably
also be useful for additional usecases.