On Mar 17, 2006, at 12:54 PM, Kumar Gala wrote:
I'm looking at porting the i2c-virtual code from 2.4 to 2.6. One
thing I'm not clear on is the use of i2c_add_adapter_nolock() by
the old code. The only reference I can find related to this is:
http://archives.andrew.net.au/lm-sensors/msg31060.html
I can't think of a reason why locking would be in issue when adding
or removing of a virtual adapter. Anyone have an additional ides
on this?
Ok, so I figured out why the _nolock() versions exist. In
i2c_driver_register we take the core_list lock. Eventually we will
call i2c_probe() which should call driver->attach_adapter(). For a
virtual bus the driver's attach_adapter() will end up calling
i2c_virt_create_adapter() which will end up calling i2c_add_adapter()
which will never get the core_list lock.
So should we integrate the concept of virtual adapters into the i2c
core and have it such that i2c_virt_create_adapter()/
i2c_virt_remove_adapter() expects the caller to have the core_list
lock already?
- kumar
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