Commit bd0e6c9614b9 ("usb: hub: try old enumeration scheme first for high speed devices") changed the way the hub driver enumerates high-speed devices. Instead of using the "new" enumeration scheme first and switching to the "old" scheme if that doesn't work, we start with the "old" scheme. In theory this is better because the "old" scheme is slightly faster -- it involves resetting the device only once instead of twice.
However, for a long time Windows used only the "new" scheme. Zeng T said that Windows 8 and later use the "old" scheme for high-speed devices, but apparently there are some devices that don't like it. William B reports that the Ricoh webcam built into his Sony Vaio laptop not only doesn't enumerate under the "old" scheme, it gets hung up so badly that it won't then enumerate under the "new" scheme! Only a cold reset will fix it.
Therefore we will revert the commit and go back to trying the "new" scheme first for high-speed devices.
Joined: 12 May 2008 Posts: 2190 Location: N.E. USA
Posted: Sat 02 May 2020, 22:16 Post subject:
I've seen this quite a bit in several series 4/5 kernels. While not modern, the 3.16.83 rev has fewer reverts, and infrequently updated. _________________ Linux user #498913 "Some people need to reimagine their thinking."
"Zuckerberg: a large city inhabited by mentally challenged people."
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