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
