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    SubjectRe: [RFC PATCHv2] usb: USB Type-C Connector Class
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    On Wed, 2016-06-22 at 12:31 +0300, Heikki Krogerus wrote:

    Hi,

    > > Now correct me, if I am misreading the spec. I am sure the system
    > > will boot unless it needs ridiculous amounts of power, but
    > > will we see anything on the screen? As far as I can tell the spec
    > > actually says that you cannot enter an alternate mode without having
    > > established a power contract.
    > > If we really leave entering modes up to user space, we have lost
    > > printk before getting into the initrd at the earliest.
    >
    > With these boards, you will not see anything on the screen that is
    > attached to a Type-C connector until the OS has booted to the point
    > where it has negotiated the power contract and entered a mode.
    >
    > If the system has BIOS/FW/EC capable of negotiating the power contract
    > and enter a mode, but where we still are expected to take over the
    > whole TCPM in OS, I think the connection will be reset.

    Think about a DP over type C display with a USB PD power brick on a
    daisy chain.
    If the host needs more than 15W or more than 5V, a reset is suicide.

    And losing earlyprintk hurts a lot.
    This means we need USB PD statically in the kernel. And a kernel
    based policy that brings up all displays.

    Regards
    Oliver


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