On Tue, Apr 14, 2009 at 1:35 PM, Arjun Joshi <arjun.joshi@xxxxxxxxxxxxxx> wrote: > Hi All, > > I am new to this mailing list and to the linux kernel. So the question below > might seem a little simple. Ok here goes.. > > I read that "struct bus_type" object is registered with the driver core when > the specific subsytem is loaded in the kernel. > > Now in context of USB, I want to know at which point is the USB subsystem > loaded in the kernel and what will be the next sequences of registrations > in the driver core? > it is in drivers/usb/core/usb.c: 1088 subsys_initcall(usb_init); which insert the function usb_init() to be called during subsystem initialization. tracing further, inside usb_init(): 1018 retval = bus_register(&usb_bus_type); 1019 if (retval) 1020 goto bus_register_failed; 1021 retval = bus_register_notifier(&usb_bus_type, &usb_bus_nb); 1022 if (retval) 1023 goto bus_notifier_failed; 1024 retval = usb_host_init(); 1025 if (retval) 1026 goto host_init_failed; 1027 retval = usb_major_init(); 1028 if (retval) 1029 goto major_init_failed; 1030 retval = usb_register(&usbfs_driver); 1031 if (retval) 1032 goto driver_register_failed; 1033 retval = usb_devio_init(); 1034 if (retval) 1035 goto usb_devio_init_failed; 1036 retval = usbfs_init(); 1037 if (retval) 1038 goto fs_init_failed; 1039 retval = usb_hub_init(); and the function call usb_register(&usbfs_driver) gave rise to the earliest usb message in dmesg output as below: 278 usbcore: registered new interface driver usbfs 279 usbcore: registered new interface driver hub 280 usbcore: registered new device driver usb 281 PCI: Using ACPI for IRQ routing hope these helped. > In the linux kernel the "struct device" or "struct device_driver" object are > embedded in a higher layer structure. What is the reason for designing the > kernel in the above way? > it is called drivers model. Meant for function calls propagation downwards, as objects are registered below one another. And it aimed to be generic enough to be used across many variation in hardware types. read this (in kernel source): Documentation/driver-model: porting.txt platform.txt overview.txt interface.txt driver.txt devres.txt class.txt bus.txt binding.txt device.txt -- Regards, Peter Teoh -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
