linux-kernel - Re: Userspace I/O driver core

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Date:	Thu, 14 Dec 2006 09:54:48 -0800
From:	Greg KH <greg@...ah.com>
To:	Avi Kivity <avi@...o.co.il>
Cc:	arjan@...radead.org, linux-kernel@...r.kernel.org,
	tglx@...utronix.de
Subject: Re: Userspace I/O driver core

On Thu, Dec 14, 2006 at 12:56:29PM +0200, Avi Kivity wrote:
> Arjan van de Ven wrote:
> >On Thu, 2006-12-14 at 12:46 +0200, Avi Kivity wrote:
> >  
> >>Arjan van de Ven wrote:
> >>    
> >>>>I understand one still has to write a kernel driver to shut up the irq. 
> >>>>How about writing a small bytecode interpreter to make event than 
> >>>>unnecessary?
> >>>>    
> >>>>        
> >>>if you do that why not do a real driver.
> >>>
> >>>  
> >>>      
> >>An entire driver in bytecode? 
> >>    
> >
> >no a real, non-bytecode driver.
> >
> >  
> 
> Isn't the whole point of uio is to avoid writing a kernel mode driver?

No.  Did you read the documentation that is written about the uio core?

> As proposed, it doesn't quite accomplish it.  With an additional 
> bytecode interpreter, you can have a 100% userspace driver (the bytecode 
> interpreter would be part of uio, not the driver).

If you want to try to work on something as complex as a bytecode
interpreter that can handle all of the hookups to the pci and other
kernel subsystems that are necessary to get such a driver to work
properly, feel free to.

But until then, you'll have to stick with a tiny kernelspace driver that
handles the basic hardware discovery and initialization logic.

Which, for everyone that I have talked to that needs such a driver, is
not a problem at all.

thanks,

greg k-h
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