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    SubjectRe: [PATCH 12/12] usb: use IRQ watching
    On Tue, Jun 15, 2010 at 13:05, Jean Delvare <> wrote:
    > On Tue, 15 Jun 2010 12:30:00 +0200, Kay Sievers wrote:
    >> On Tue, Jun 15, 2010 at 00:19, Tejun Heo <> wrote:
    >> > Hmm... maybe what we can do is generating an uevent when an IRQ is
    >> > confirmed to be bad and then let udev notify the user.  That way we'll
    >> > probably have better chance of getting bug reports and users have
    >> > whiny but working system.
    >> Not really, uevents are not picked up by anything that could report an
    >> error to userspace, they are just seen by udev. Also uevents are
    >> usually not the proper passing method. They are not meant to ever
    >> transport higher frequency events, or structured data. They cause to
    >> run the entire udev rule matching machine, and update symlinks and
    >> permissions with every event.
    >> We will need some better error reporting facility. On Linux you don't
    >> even get notified when the kernel mounts your filesystem read-only
    >> because of an error. It will only end up in 'dmesg' as a pretty much
    >> undefined bunch of words. :)
    >> We will need some generic error reporting facility, with structured
    >> data exported, and where userspace stuff can subscribe to.
    >> Uevents/udev can not really properly provide such infrastructure.
    >> Maybe that can be extended somehow, but using kobject_uevent() and
    >> trigger the usual udev rule engine is not what we are looking for, for
    >> sane error reporting.
    > Random idea of the day (I don't know anything about it all): let the
    > kernel connect to D-Bus and use it somehow?

    Yeah, D-Bus is an peer-to-peer IPC mechanism/protocol. The D-Bus
    daemon can filter and multiplex/distibute messages.

    It's very similar to what we can do with netlink. The netlink
    multicast stuff can even provide lots of the functionality the D-Bus
    daemon provides.

    I think we should avoid the D-Bus complexity for the very low-level
    stuff. Very much like udev is not using it, but has efficient
    in-kernel message filtering based on Berkeley Packet Filters, and
    multiple listeners event subscription/distribution based on netlink
    multicast functionality.

    Not sure if netlink is the right answer here, but it's surely easier
    to handle than D-Bus, and would provide a very similar functionality.

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