Date: Thu, 22 Feb 1996 09:52:18 +0530 From: A JOSEPH KOSHY <koshy@india.hp.com> To: Masahiro SEKIGUCHI <seki@sysrap.cs.fujitsu.co.jp> Cc: hackers@FreeBSD.org, smpatel@wam.umd.edu Subject: Re: ISA device irq/mem auto-configuration Message-ID: <199602220422.AA051632939@fakir.india.hp.com> In-Reply-To: Your message of "Wed, 21 Feb 1996 22:30:57 %2B0900." <199602211330.WAA00818@sphinx.sysrap.cs.fujitsu.co.jp>
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>>>>> ms == Masahiro SEKIGUCHI said: >>>>> ms> For IRQ, DMA channel, and/or memory addresses, I support the idea that ms> the driver should use the value detected at boot, *if* the driver can ms> DETECT them but can NOT set them. A question here: if a card is determined (by reading the hardware) to reside at port 0x300 and IRQ 5, can we change the kernel isa_dev structure overwriting the configured values in the structure? The question is: Is this a safe thing to do in general? --- ms> If those settings can be changed by the driver, it *may* be better to ms> use values specified in the config. I cannot just say one scenario is ms> better, in this case. My thinking was that reconfiguring the hardware shouldn't be part of the regular driver. For one it violates the principle of least surprise; for example if a user is running DOS and FreeBSD. We would want the BSD driver to change settings on the card every time it boots forcing the user to re-run his DOS config utilities everytime. Secondly, configuring software configurable cards adds another magnitude of complexity and board model dependence to the driver. Thirdly, FreeBSD's pre-configured idea of interrupts and IO addresses may clash with some other hardware present on the system. So I thought it was better for FreeBSD to obey the hardware settings instead of the other way round. --- Koshy
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