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    SubjectRe: OpenGL-based framebuffer concepts
    On 5/30/06, Dave Airlie <airlied@gmail.com> wrote:
    > Actually the suspend/resume has to be in userspace, X just re-posts
    > the video ROM and reloads the registers... so the repost on resume has
    > to happen... so some component needs to be in userspace..

    I'd like to see the simple video POST program get finished. All of the
    pieces are lying around. A key step missing is to getting klibc added
    to the kernel tree which is being worked on.

    BenH has the emu86 code. I agree that is simpler to always use emu86
    and not bother with vm86. He also pointed out that we need to copy the
    image back into the kernel after the ROM runs. Right now you can only
    read the ROM image from the sysfs attribute. The ROM code has support
    for keeping an image in RAM, it just isn't hooked up to the sysfs
    attribute for writing it.

    The pci device struct tracks primary vs secondary cards. How does this
    reposting work on laptops where the primary ROM may not really be
    there? We have the shadow copy, is it always safe to rerun it?

    At boot, inside the kernel device driver of the video card there would
    be a small piece of logic that check the pci device struct, if
    secondary it uses call_userspace() to trigger the reset program. The
    driver has to suspend at this point until user space hits an sysfs
    attribute and tells it that it is safe to proceed. This mechanism will
    allow us to reset secondary cards at boot.

    Small programs like this are the same way I would handle mode setting
    for cards that have to do it in user space. A normal user could use an
    IOCTL to set the mode and then the driver uses call_userspace() to do
    the actual mode setting in root context. This lets you set your mode
    without being root and it stops you from setting the mode on video
    hardware that you don't own. Everything happens through a device node
    making it easy for PAM to assign ownership.

    --
    Jon Smirl
    jonsmirl@gmail.com
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