Subject: New pseudo bus, new device
To: None <>
From: Gary Thorpe <>
List: tech-kern
Date: 05/07/2002 23:03:50

I am currently porting the ppc driver from FreeBSD to NetBSD (this is a low 
level driver for a AT-style parallel port chipset). While this work is 
progressing nicely (device can be probed, attached and configured for 
generic chipsets), it is still ongoing (specific chipset probes are not used 
right now). The ppc driver is MI as far as I can tell (currently this ppc 
device exists on the ISA bus, because that is my machines setup). I believe 
'AT-style' parallel ports do exist on non-x86 machines (some alphas).

My main concern is the next major step in porting. I am at a loss on how to 
implement the ppbus 'pseudo' bus on top of this ppc device. The ppbus bus is 
used by almost all of the higher level drivers in the FreeBSD code, so 
reusing it is critical to port these drivers over (the drivers include lpt, 
iomega zip, ieee 1248, and PLIP). The reason this code is worth porting over 
is because NetBSD's current lpt support only supports centronics mode 
printers, while the FreeBSD code can use newer standards and support faster 
devices (as well as PLIP, which may be useful for systems with limited 
communications options).

I am trying to look at ATAPI and SCSI for examples of higher level buses 
which 'attach' to lower level devices, but I am wondering if there is any 
standard/specific way to accomplish this on NetBSD. I would appreciate any 
comments, suggestions or indications on how to proceed.


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