Changes between Version 18 and Version 19 of USB


Ignore:
Timestamp:
07/26/2021 03:35:51 PM (3 years ago)
Author:
Tim Harvey
Comment:

added section about runtime driver binding

Legend:

Unmodified
Added
Removed
Modified

  • USB

    v18 v19  
    326326== Linux USB Auto-suspend
    327327USB autosuspend is problematic with several embedded SoC's due to host controller chip errata. This is the case for both the i.MX6 on Ventana and the CN80XX on Newport. To work around these errata we find it safest to just disable USB autosuspend with a kernel command-line argument of 'usbcore.autosuspend=-1'. This is done in several of our bootscripts.
     328
     329
     330[=#driver-binding]
     331== Driver Binding based on Vendor ID and Device ID
     332USB drivers bind to devices based on 16bit vendor ID device ID numbers that the card reports during bus enumeration.
     333
     334Sometimes a new USB device is not bound to a driver because it's ID's have not yet been added. You can overcome this at runtime by adding the hex ID's via the drivers sysfs 'new_id' node.
     335
     336For example, to allow the qmi_wwan driver to bind to a card who's VID/PID is 0x1bc7 0x110a:
     337{{{#!bash
     338echo "1bc7 110a" > /sys/bus/usb/drivers/qmi_wwan/new_id
     339}}}