Re: Exposing ROM's though sysfs

From: Jon Smirl (jonsmirl_at_yahoo.com)
Date: 07/30/04

  • Next message: Andrew Morton: "Re: [PATCH] Improve pci_alloc_consistent wrapper on preemptive kernels" 
    Date:	Fri, 30 Jul 2004 13:03:59 -0700 (PDT)
To: Martin Mares <mj@ucw.cz>

    From what I know minimal decoder cards are ancient PCI cards. None of
    the current hardware does this.

    Caching would only occur:
    1) when a kernel driver for the card loads
    2) and if the kernel driver asks for it

    So normal hardware would never ask for the cache since it isn't needed.
    In the normal hardware case direct ROM access is used. If the
    minimalistic hardware is using a user space driver it won't ask for the
    cache either. The only time you get cached is on minimal hardware and
    when the driver asks for it. Since the driver is asking for the cache
    you have to assume that it needs it so the memory isn't wasted.

    --- Martin Mares <mj@ucw.cz> wrote:

    > Hello!
    >
    > > The caching is only going to happen for cards with minimal address
    > > decoder implementations. As far as I know there is only one card
    > that
    > > does this.
    >
    > Yes, but ...
    >
    > (1) it doesn't change the fact that the caching is in the vast
    > majority
    > of cases just wasting of RAM, even if it will happen only with a
    > couple
    > of cards.
    >
    > (2) not all drivers dwell in the kernel.
    >
    > I would prefer keeping sysfs access the ROM directly, with a little
    > work-around disabling the sysfs file for the devices known for
    > sharing
    > decoders and to offer a boot-time parameter for forcing the copy in
    > case
    > you really need such feature for that particular device.
    >
    > Have a nice fortnight
    > --
    > Martin `MJ' Mares <mj@ucw.cz>
    > http://atrey.karlin.mff.cuni.cz/~mj/
    > Faculty of Math and Physics, Charles University, Prague, Czech Rep.,
    > Earth
    > return(EIEIO); /* Here-a-bug, There-a-bug... */
    >

    =====
    Jon Smirl
    jonsmirl@yahoo.com

                    
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  • Next message: Andrew Morton: "Re: [PATCH] Improve pci_alloc_consistent wrapper on preemptive kernels"

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