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    SubjectRe: [linux-pm] Re: [2/3] 2.6.22-rc2: known regressions v2

    Chris Newport wrote:
    >
    > Sorry, I did not make myself clear.
    >
    > Linus Torvalds wrote:
    >
    >> On Fri, 25 May 2007, Chris Newport wrote:
    >>
    >>
    >>> Maybe we should take a hint from Solaris.
    >>>
    >>
    >> No. Solaris is shit. They make their decisions based on "we control
    >> the hardware" kind of setup.
    >>
    >>
    > Not really a Solaris feature. This is a feature of the Openboot PROM
    > which is also used by several other vendors.
    > The Openboot PROM knows how to write to disk. The same should
    > apply on Apple hardware and others which use the openboot
    > convention.

    It doesn't, though. It is not part of any specification of Open Firmware
    that you MUST be able to write to any exposed disk. In fact, I know of
    one firmware implementation (ours) where we don't allow it. Apart from
    being a bitch to implement safely (i.e. for people's data) it is also
    quite a security problem to allow the firmware interface to write to
    the disk. You can't make the differentiation between "at the firmware
    console" and "inside a booted OS" unfortunately.

    The 'solution' in Solaris is actually that the filesystem and disk
    write handling is done by the OS bootloader and not the PROM. All
    the PROM knows how to do is read off the bootloader (in a special
    partition in a special filesystem format) and execute it after
    probing the hardware and providing the device tree. The first stage
    boot loader then knows how to read UFS filesystems so it can grab
    the kernel and load kernel modules, and write back a kernel dump
    if it needs to.

    That, and Linux drops OF support like a lead weight very early in boot.
    About all you can rely on is the device tree listing all your disks
    present, and even then, Linux will redetect all of these with native
    drivers and give them new names anyway. In fact, Solaris does the
    same (but it is better about associating the device tree entries
    than Linux)

    --
    Matt Sealey <matt@genesi-usa.com>
    Genesi, Manager, Developer Relations
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