Re: binary drivers and development

[John Richard Moser <nigelenki@comcast.net>]

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Peter Chubb wrote:
>>>>>>"John" == John Richard Moser <nigelenki@comcast.net> writes:
> 
> 
> 
> John> I've done more thought, here's a small list of advantages on
> John> using binary drivers, specifically considering UDI.  You can
> John> consider a different implementation for binary drivers as well,
> John> with most of the same advantages.
> 
> Almost all these advantages are also present for user-mode drivers...
> and getting drivers out of the kernel, where possible, is a much
> better approach IMHO than trying to maintain a leaky in-kernel
> interface.  The problem with in-kernel interfaces, even if set in
> concrete, is that any binary driver can go outside the interface ---
> there's no encapsulation --- and so break when the kernel changes.
> 

CPL=3 scares me; context switches are expensive.  can they have direct
hardware access?  I'm sure a security model to isolate user mode drivers
could be in place. . .

. . . huh.  Xen seems to run Linux at CPL=3 and give direct hardware
access, so I guess user mode drivers are possible *shrug*.  Linux isn't
a microkernel though.

> Peter C
> 
> 
> 

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