Date: Fri, 20 Sep 1996 11:01:17 -0700 From: Amancio Hasty <hasty@rah.star-gate.com> To: Janice McLaughlin <janus@freegate.net> Cc: "'hackers@freebsd.org'" <hackers@FreeBSD.org> Subject: Re: Plug and Play naivety Message-ID: <199609201801.LAA04635@rah.star-gate.com> In-Reply-To: Your message of "Fri, 20 Sep 1996 10:42:57 PDT." <01BBA6E0.7D655A60@ws40.freegate.net>
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>From The Desk Of Janice McLaughlin : > > I'm writing a device driver for an ISA card with the Plug and Play > chip on it and have a few questions. (I'm not new to device drivers > but am definately new to ISA and x86 class machines). I'm > runing on 2.2-960801-SNAP. > > A search of the archives shows me that at least I'm not alone > in my problems with PnP. I have also downloaded the latest code > from Sujal Patel on freefall.freebsd.org for PnP support. > > 1. mail from Sujal notes that "if your motherboard supports PnP > devices, then you don't need this code". What does this mean? > I've been told that the BIOS on the machine I'm using has > "Plug and Play" support ... does this mean it's possible that the > BIOS has queried the ISA devices on boot and already has all the > config info? Can I get at this somehow from the kernel? Or is this > only referring to PCI kind of Plug and Play? Some devices may need further initialization and for this you will need driver support. For instance, the GUS PnP after the BIOS or the driver activates the card , the driver then does further initialization specific to the card. The card specific initialization or configuration is usually not due to PnP . Citing again, the GUS cards prior to their PnP implementation one could software program the dma and irq settings for the card. In my case, because it is often difficult for users to modify kernel files, the driver has special hooks so that if the kernel via the kernel configuation passess all the configuration information to the driver , the driver will initialize the card according to the supplied information. The effect is that manually configuring a GUS PnP looks pretty much like any old ISA device in the kernel configuration file. This is useful for cases in which the BIOS PnP implementation is broken , makes a mistake in initializing the card, or the motherboard does not support PnP. > 2. I notice that the recommendation for other cards (eg: 3c509) > is to turn "off" PnP. That's sounds great ... how do I do that? Is > it card specific? When you do this to a (for example) 3c509, does > it stay off only until the next power up? or is there some NVRAM > somewhere that can store this info so you don't have to reconfig > it each time you reboot? Not all ISA PnP devices have a mechanism to disable PnP. Enjoy, Amancio
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