Re: Linux USB Documentation

May be Srinivas is just learning the higher level codes which call his
USB driver - as I understand - and so the following is my attempt in
this aspect.   Please criticize if there is any error.

First, is the rest_init() function (don't ask who called this
function), which will setup a kernel thread calling kernel_init().

Then kernel_init()  (init/main.c)==> do_basic_setup():

static void __init do_basic_setup(void)
{
        /* drivers will send hotplug events */
        init_workqueues();
        usermodehelper_init();
        driver_init();
        init_irq_proc();
        do_initcalls();
}

And driver_init() is as follows - note the ordering of
devices-specific drivers, bus, and finally class drivers.

void __init driver_init(void)
{
        devices_init();
        buses_init();
        classes_init();
        firmware_init();
        hypervisor_init();
        platform_bus_init();
        system_bus_init();
        cpu_dev_init();
        memory_dev_init();
        attribute_container_init();
}

And do_initcalls() (a summary article is here:
http://lwn.net/Articles/141730/) will go through all the different
subsys_initcall(), including one of which is subsys_init(usb_init) ==>
calling usb_init() in usb/core/usb.c, and this function will execute
the following list of function in sequence (the ordering of the
function calls is what u are looking for right, I supposed?):

	retval = ksuspend_usb_init();
	retval = bus_register(&usb_bus_type);
	retval = usb_host_init();
	retval = usb_major_init();
	retval = usb_register(&usbfs_driver);
	retval = usb_devio_init();
	retval = usbfs_init();
	retval = usb_hub_init();
	retval = usb_register_device_driver(&usb_generic_driver, THIS_MODULE);

And from these high level function I think it is easier to proceed
ahead with the source code analysis now :-).

On Nov 17, 2007 12:17 AM, Alan Stern <[email protected]> wrote:
> On Fri, 16 Nov 2007, Srinivas G. wrote:
>
> > Dear All,
> >
> > I am a Linux device driver developer. I have developed the USB client
> > driver in the Linux environment. For this, I have followed the Rubini's
> > 3rd Edition LLD book. Now I want to know the interaction among the Linux
> > OS, USB Stack and HCD (Host Controller Driver). I mean, what are the
> > modules exists in the stack and how they interacts with the OS as well
> > as HCD? Suppose, how the HCD driver intimates the stack about when a new
> > device attached to the host controller? I think, it is through some
> > event mechanism, but I need code flow.
>
> > I have gone through the following links.
> > http://www.linux-usb.org
> > http://www.linux-usb.org/USB-guide/book1.html
> > http://it.linux-usb.org/FAQ.html
> > http://tldp.org/
> > http://www.tux.org/lkml/index.html
> > http://www.linux-usb.org/usb2.html
> >
> > I did not get the information that I need (that is flow among OS, Stack
> > and HCD). All these links have old information and I am looking into the
> > latest kernel version 2.6.22.
> >
> > So I would be happy if you could provide me some pointers (links) or
> > some good explanation on it.
>
> There is no detailed documentation; there is only the source code.
>
> If you have some specific questions, you can post them to the mailing
> list.
>
> Alan Stern
>
>
>
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-- 
Peter Teoh
HP: 96809281

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