Re: [discuss] Re: kgdb for x86_64 2.6 kernels

[George Anzinger <george@mvista.com>]

Greg KH wrote:
> On Wed, Jan 14, 2004 at 04:02:45PM -0800, George Anzinger wrote:
> 
>>Greg KH wrote:
>>
>>>On Wed, Jan 14, 2004 at 12:02:02PM -0800, George Anzinger wrote:
>>>
>>>
>>>>Right.  I had hoped that we might one day be able to use the USB and I am 
>>>>sure there are others.
>>>
>>>
>>>Raw USB?  Or some kind of USB to serial device?
>>>
>>>Remember, USB needs interrupts to work, see the kdb patches for the mess
>>>that people have tried to go through to send usb data without interrupts
>>>(doesn't really work...)
>>
>>I gave up on USB when I asked the following questions:
>>1. How many different HW USB master devices need to be supported (i.e. 
>>appear on your normal line of MBs)? (answer, too many)
> 
> 
> There are only 3, UHCI, OHCI, and EHCI.  You can forget about EHCI, as
> all EHCI controllers contain either a UHCI or OHCI controller embedded
> in them (EHCI only handles the USB2 high speed data.)  So you really
> only have to handle 2.
> 
> 
>>2. Can I isolate a USB port from the kernel so that it does not even know 
>>it is there? (answer: NO)
> 
> 
> Sorry, this is correct.  Unless you want to take over the whole pci
> device that the USB controller is on.  That's a possiblity you might
> want to look into.

Each cpu, usually, has several USB controllers.  I would only want to take over 
one.  Is that possible?  If not, it means we can not debug USB drivers...


-- 
George Anzinger   george@mvista.com
High-res-timers:  http://sourceforge.net/projects/high-res-timers/
Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml