Re: [PATCH] add PCI ROMs to sysfs

From: Alan Cox (alan_at_lxorguk.ukuu.org.uk)
Date: 08/12/04

  • Next message: Jack Steiner: "Re: [Lse-tech] [PATCH] cpusets - big numa cpu and memory placement" 
    To: Jon Smirl <jonsmirl@yahoo.com>
Date:	Thu, 12 Aug 2004 12:51:32 +0100

    On Iau, 2004-08-12 at 00:31, Jon Smirl wrote:
    > How are we supposed to implement this without a copy? Once the device
    > driver is loaded there is never a safe way access the ROM again because
    > an interrupt or another CPU might use the PCI decoders to access the
    > other hardware and disrupt the ROM read. You have to copy the ROM when
    > the driver says it is safe.

    It's never safe essentially. The only way you can make it safe for this
    case is to put the knowledge in the device driver for that specific card
    rather than sysfs.

    > Still another scheme would be to make the drivers for this class of
    > card implement a lock around PCI address decoder use. That would get
    > complex with interrupt routines.

    That would be impossible in fact because of DMA and SMM activity.

    > How much trouble do we want to go to handling a case that only applies
    > to very few cards? I believe old QLogic disk controllers have this
    > problem, are there others? I'm not aware of any video cards with this
    > problem. 99%+ of PCI ROMs don't need the copy.

    It would be better to just to blacklist those corner cases

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  • Next message: Jack Steiner: "Re: [Lse-tech] [PATCH] cpusets - big numa cpu and memory placement"

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