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    SubjectRe: USB gadget with drivers "on board"
    Michał Nazarewicz schrieb:
    > On Mon, 26 Apr 2010 22:14:54 +0200, Josua Dietze
    > <digidietze@draisberghof.de> wrote:
    >
    >> Important for the Linux handling is that "mode 1" is clearly
    >> distinguishable from "mode 2", either by using a different product ID
    >> or by setting a different class for the device or interface 0 (will
    >> most likely be "8" for the install mode).
    >
    > So it will be enough to change the USB device class for the zeroth
    > interface for udev to recognise the mass storage to be ejected? Note
    > that I will use mass storage in the second mode as well.

    This is often the case with the common "zero-cd" devices, but
    they have the storage on upper interface numbers after switching.

    The point is to enable udev or any other tool to distinguish
    between "unswitched" and "switched"; otherwise the procedure
    for switching will be executed on *both* modes which might
    disturb the device or the system.

    A change in one of the attributes like iProduct or iSerial
    could be detected as well of course.

    > Also, I think that it might be a good idea to make some "standardised"
    > mechanism for all such devices so that a generic udev code could be
    > written. Adding things to the descriptors may be difficult in a way,
    > but maybe adding "[NoCD]" to the interface name would be enough.

    That is up to the (countless) manufacturers of course; on the
    other hand, the Windows drivers need to recognize the mode as
    well so there should always be one way or the other to
    accomplish that.


    Josua Dietze
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