[i2c] Identifying I2C busses

[David Brownell]

On Wednesday 07 March 2007 12:42 pm, David Brownell wrote:

>		 But again, I may decide I like your
> notion of device struct as handle, at which point this issue vanishes too.

OK, unfortunately that idea can't work.  I should have remembered:

    /sys/devices/pci0000:00/0000:00:01.1> ls
    broken_parity_status  device  i2c-1       msi_bus    resource5         uevent
    bus                   driver  irq         power      subsystem         vendor
    class                 enable  local_cpus  resource   subsystem_device
    config                i2c-0   modalias    resource4  subsystem_vendor
    /sys/devices/pci0000:00/0000:00:01.1> 

Note: both i2c-0 and i2c-1 are parented by the same PCI device.

On embedded systems there's essentially always a one-to-one mapping between
driver model devices and I2C busses.  But that's not true on many common
PCI based systems ... like the one above, and various video adapters.

Unless that mapping is one-to-one, there's no way to use physical device
nodes as the persistent identifiers for I2C busses.  So, when I refresh
that patch it's going to still use bus numbers as handles.

- Dave