On Fri, 20 Feb 1998 14:29:20 -0500 
 Thor Lancelot Simon <tls@panix.com> wrote:

 > The problems seem to mostly be with newer disks or disks which are very
 > aggressive about tagged queueing, AFAICT.  It's noteworthy that even the
 > ahc (AIC7XXX) driver, which many people are so fond of, totally loses with
 > some such disks -- I have a Quantum Atlas II which is basically useless with
 > the ahc unless I turn off tagged queueing in the driver.

Yes, tagged queueing seems to be the common factor is almost all of
the reported problems.

 > And, once more: it's the *exact same* driver that's in FreeBSD.  The only
 > difference which seems noteworthy to me is that in FreeBSD, the driver makes
 > sure the command script is in physically contiguous RAM, but the last time
 > I looked there was no interface to do that under NetBSD.  I doubt that that

Yes, there is.  bus_dmamem_alloc(), part of the bus_dma(9) suite.

 > We have another NCR 53c[78xx] driver in the tree, actually.  As well as a nice
 > script assembler which would make writing a new, clean ncr driver fairly easy.
 > What should really happen, if anyone is looking for a project, is that the
 > existing 53c7XX driver should become bus-independent, learn about tagged
 > queueing and cards with different kinds of script storage (the newer 8xx chips
 > have a local script cache as well as the ability to get scripts from host
 > RAM), and get bus front-ends which would replace the existing PCI 53c8xx
 > attachment and the VME (is there another?) 53c7xx attachment.
 > 
 > That really wouldn't be so painful.  Most of the code is already done.

The other driver is the "siop" driver, in the Amiga port.  It supports the
53c710 and 53c725 (perhaps; not sure on the latter).  As I recall, some
research indicated that a single driver would not be possible for the
53c710 and 53c8xx, but a good chunk of the code could be shared.

Charles knows the details of this, I think...

Jason R. Thorpe                                       thorpej@nas.nasa.gov
NASA Ames Research Center                            Home: +1 408 866 1912
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