Message-ID: <40060966.80204@mvista.com>
Date: Wed, 14 Jan 2004 19:30:46 -0800
From: George Anzinger <george@mvista.com>
Organization: MontaVista Software
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To: Greg KH <greg@kroah.com>
CC: Matt Mackall <mpm@selenic.com>, "Amit S. Kale" <amitkale@emsyssoft.com>,
       Andrew Morton <akpm@osdl.org>, jim.houston@comcast.net,
       discuss@x86-64.org, ak@suse.de, shivaram.upadhyayula@wipro.com,
       lkml <linux-kernel@vger.kernel.org>, Pavel Machek <pavel@ucw.cz>
Subject: Re: [discuss] Re: kgdb for x86_64 2.6 kernels
References: <000e01c3d476$2ebe03a0$4008720a@shivram.wipro.com> <200401101611.53510.amitkale@emsyssoft.com> <400237F0.9020407@mvista.com> <200401122020.08578.amitkale@emsyssoft.com> <40046296.1050702@mvista.com> <20040114063155.GF28521@waste.org> <4005A03A.40409@mvista.com> <20040114232631.GB9983@kroah.com> <4005D8A5.3010002@mvista.com> <20040115002334.GC10153@kroah.com>
In-Reply-To: <20040115002334.GC10153@kroah.com>
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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

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