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    SubjectRe: [PATCH V4] leds: trigger: Introduce an USB port trigger
    On 4 September 2016 at 02:24, Alan Stern <stern@rowland.harvard.edu> wrote:
    > On Sat, 3 Sep 2016, Jacek Anaszewski wrote:
    >
    >> >> The remaining issue is the sysfs interface design for defining and
    >> >> presenting multiple USB ports. I'm still in favour of a single
    >> >> attribute with space separated list. This scheme is commonly used
    >> >> in existing interfaces.
    >> >
    >> > No such interface is needed if you do things the way I outlined above.
    >> > Each trigger would require the user to specify either one port, one
    >> > hub, or nothing at all. Multiple ports would not be used.
    >>
    >> The patch assumes that it is possible to register trigger for many
    >> ports.
    >
    > The patch could be changed to remove that assumption.

    I did this assumption for a reason. There are many devices with more
    than 1 USB port and these ports are handled by the same controllers,
    just different ports. Let me share USB details of my SmartRG SR400ac
    device with 2 physical USB ports:

    Physical USB 3.0 port is handled by following controllers and their
    root hub ports:
    1) OHCI's port 1
    2) EHCI's port 1
    3) XHCI's port 1

    Physical USB 2.0 port is handled by following controllers and their
    root hub ports:
    1) OHCI's port 2
    2) EHCI's port 2


    This devices has 3 separated LEDs. I'll list them and tell which ports
    should be assigned to them:

    bcm53xx:green:usb3 should have assigned:
    1) OHCI's port 1
    2) EHCI's port 1

    bcm53xx:white:usb3 should have assigned:
    1) XHCI's port 1

    bcm53xx:white:usb2 should have assigned:
    1) OHCI's port 2
    2) EHCI's port 2


    As you can see, I need to specify ports precisely. Assigning a single
    port is not enough. Assigning whole hub is too much. So none of:
    > echo usb1-4.2 >/sys/class/led/foo/trigger
    > echo hub1-4 >/sys/class/led/foo/trigger
    > echo usb >/sys/class/led/foo/trigger
    would be sufficient here :(

    --
    Rafał

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