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SubjectRe: [OT] RE: UDI and Free Software
Date
In article <linux.kernel.199810071736.NAA05114@dcl.mit.edu>,
Theodore Y. Ts'o <tytso@MIT.EDU> wrote:
>
> > to native drivers... For some hardware it may not make a difference
> > (for example, a scanner). But for other hardware (such as a gigabit
> > ethernet board), my guess is that UDI will be a disaster as far as
> > performance is concerned.
>
> UDI has no concept of other interface libraries or access API's - so
> it lacks stuff like check_region that is central to the Linux philosophy.
> UDI on Linux would also be useless for parallel scanners - UDI can't
> describe talking to the parport management layer
>
>Exactly. So you'd have to do an extra memory copy in the Linux<->UDI
>interface layer.

I guess it depends on the driver. I looked at one of the scsi
drivers to see just what check_region() was used for
(2.0.28:advansys.c, which is a device driver from a vendor, and thus
more likely to be udi'zed if a udi driver interface went into the
kernel and to my application programmer eyes it looks like all it
uses check_region() for is while probing for devices. Now, if we
need to use check_region() to make sure we don't stomp on other
device while we're doing probing, I'm assming that all the other
Unices out there need to do something much the same <provided, of
course, that they aren't stuuupid(tm) and will let drivers trash
the system while they're loading> while they're detecting devices,
but alas there is no large SAMPLE.IMPLEMENTATION directory on
the website for UDI.)

>It'll be slow, but you an make it work.

I've looked through a few of the scsi drivers, seeing what
check_region() is used for. It looks like it's used for
initialization and nothing else? If this is the case, do we care
about Blinding Speed(tm) -- There may be people out there agitating
for the fastest possible driver initialization, but, at least for
disk devices you spend a lot more time actually waiting for the
disks to identify themselves than you do poking at the controller.

____
david parsons \bi/ If UDI doesn't support the abstractions needed to
\/ initialize Linux device drivers, that sounds like
a good place to propose changing the standard to
fit.

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