Re: [PATCH v8] i2c: virtio: add a virtio i2c frontend driver

From: Viresh Kumar
Date: Thu Mar 18 2021 - 23:55:18 EST

On 18-03-21, 15:52, Arnd Bergmann wrote:
> Allowing multiple virtio-i2c controllers in one system, and multiple i2c
> devices attached to each controller is clearly something that has to work.


> I don't actually see a limitation though. Viresh, what is the problem
> you see for having multiple controllers?

I thought this would be a problem in that case as we are using the global
virtio_adapter here.

+ vi->adap = &virtio_adapter;
+ i2c_set_adapdata(vi->adap, vi);

Multiple calls to probe() will end up updating the same pointer inside adap.

+ vi->adap->dev.parent = &vdev->dev;

Same here, overwrite.

+ /* Setup ACPI node for controlled devices which will be probed through ACPI */
+ ACPI_COMPANION_SET(&vi->adap->dev, ACPI_COMPANION(pdev));
+ vi->adap->timeout = HZ / 10;

These may be fine, but still not ideal I believe.

+ ret = i2c_add_adapter(vi->adap);
This should be a problem as well, we must be adding this to some sort of list,
doing some RPM stuff, etc ?

Jie, the solution is to allocate memory for adap at runtime in probe and remove
the virtio_adapter structure completely.