3) following from the 2) -- why do we have to request resources in interface opening method (dev->open), if irq etc. have been already assigned to structure members earlier, when code initialized 'net_device' (for example, rtle8139 does it PCI probing routine).
A the time of net_device initialization (generally at the time of PCI probing), the irq and other resources have only been STORED in the net_device structure for future reference. They have not yet been requested from the system. The actual request for resources is delayed till the device open time because no one would actually be using those resources prior to opening the device. If we allocate the resources at initialization time only, we would be wasting precious resources without needing them, despite the same resources could have been used by some other device in use, while our device has yet not been "opened". Also consider that once we request the irq, our ISR will be called at every irq seen at that line whether it was generated by our device or not. Even if it was generated by our device, we could have safely chosen to ignore it. Hence linux delays the actual allocation of resources as much as possible. Regards, Rajat -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
