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Xref: sserve comp.os.386bsd.development:2566 comp.os.386bsd.questions:13284 Path: sserve!newshost.anu.edu.au!harbinger.cc.monash.edu.au!news.cs.su.oz.au!news.adelaide.edu.au!gateway.dircsa.org.au!cleese.apana.org.au!apanix.apana.org.au!hart From: hart@apanix.apana.org.au (Leigh Hart) Newsgroups: comp.os.386bsd.development,comp.os.386bsd.questions Subject: Kernel device driver template? Date: 20 Sep 94 13:21:26 GMT Organization: Apanix Public Access Unix, +61 8 373 5485 (5 lines) Lines: 41 Message-ID: <hart.780067286@apanix.apana.org.au> NNTP-Posting-Host: seldon.apanix.apana.org.au For a college project next year I plan to build a video frame grabber for the PC, and write a FreeBSD kernel device driver and Xwindows interface to the card. I have found a kit for the card (the hardware side of things isn't the major component of the project) and have the basic specs for interfacing to the card. Is there a device driver template available for FreeBSD (apart from snarfing the interuptless printer driver code) that I can use to write a driver for this card? It's nothing special, two byte port access (control, data) _without_ memory mapping. Frames are stored in 64K of static ram on the card, holding a 256x256 pix 256 grey scale image. Should, for example, the driver accept ioctl's for a read request and then read in the full 64K into a buffer (pointed to by ioctl argument)? Or is it more efficient to have the driver lock the card into a grab and then return one byte at a time to the calling program? I think returning a full 64k chunk would prevent the driver getting into a confused state, if for example the calling program stopped polling for bytes before the 64k was read. How would this slow down the OS if it was spending 0.N seconds in kernel mode reading 64K chunks? Any advice on this would be GREATLY appreciated :-) Also, any good references to writing an X graphics app? :-) I guess I have a few long days trawling through xv.c for inspiration otherwise :( Cheers Leigh -- | "By the time they had diminished | Leigh Hart | | from 50 to 8, the other dwarves | <hart@eppie.apana.org.au> | | began to suspect 'Hungry' ..." | C/- 195 Gilles Street | | -- Gary Larson, "The Far Side" | Adelaide SA 5006 |