From: David Liontooth <liontooth@cogweb.net>
To: linux-kernel@vger.kernel.org
Subject: USB devices fail unnecessarily on unpowered hubs
Date: Thu, 01 Jun 2006 02:18:20 -0700 [thread overview]
Message-ID: <447EB0DC.4040203@cogweb.net> (raw)
Starting with 2.6.16, some USB devices fail unnecessarily on unpowered
hubs. Alan Stern explains,
"The idea is that the kernel now keeps track of USB power budgets. When a
bus-powered device requires more current than its upstream hub is capable
of providing, the kernel will not configure it.
Computers' USB ports are capable of providing a full 500 mA, so devices
plugged directly into the computer will work okay. However unpowered hubs
can provide only 100 mA to each port. Some devices require (or claim they
require) more current than that. As a result, they don't get configured
when plugged into an unpowered hub."
http://www.mail-archive.com/linux-usb-devel@lists.sourceforge.net/msg43480.html
This is generating a lot of grief and appears to be unnecessarily
strict. Common USB sticks with a MaxPower value just above 100mA, for
instance, typically work fine on unpowered hubs supplying 100mA.
Is a more user-friendly solution possible? Could the shortfall
information be passed to udev, which would allow rules to be written per
device?
David
next reply other threads:[~2006-06-01 9:20 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-06-01 9:18 David Liontooth [this message]
2006-05-30 20:01 ` USB devices fail unnecessarily on unpowered hubs Pavel Machek
2006-06-03 9:29 ` Oliver Neukum
2006-06-05 14:32 ` [linux-usb-devel] " David Brownell
2006-06-06 7:43 ` Oliver Neukum
2006-06-08 7:01 ` Pavel Machek
2006-06-08 8:34 ` [PATCH] limit power budget on spitz Pavel Machek
2006-06-08 8:50 ` Richard Purdie
2006-06-08 9:02 ` Pavel Machek
2006-06-08 9:22 ` Richard Purdie
2006-06-08 17:09 ` Russell King
2006-06-08 18:26 ` David Brownell
2006-06-08 20:06 ` Richard Purdie
2006-06-08 20:38 ` [linux-usb-devel] " David Brownell
2006-06-08 21:22 ` Richard Purdie
2006-06-08 21:40 ` David Brownell
2006-06-08 21:49 ` Richard Purdie
2006-06-08 23:44 ` David Brownell
2006-06-09 1:25 ` Nicolas Pitre
2006-06-09 2:03 ` David Brownell
2006-06-09 2:34 ` Nicolas Pitre
2006-06-01 10:01 ` USB devices fail unnecessarily on unpowered hubs Andrew Morton
2006-06-01 11:42 ` Daniel Drake
2006-06-01 14:58 ` Alan Stern
2006-06-01 15:09 ` linux-os (Dick Johnson)
2006-06-01 15:23 ` Lennart Sorensen
2006-06-01 21:39 ` Dagfinn Ilmari Mannsåker
2006-06-01 15:53 ` Oliver Neukum
2006-06-01 17:24 ` linux-os (Dick Johnson)
2006-06-01 16:57 ` Alan Stern
2006-06-01 16:43 ` [linux-usb-devel] " Greg KH
2006-06-02 0:03 ` David Liontooth
2006-06-02 1:53 ` [linux-usb-devel] " David Brownell
2006-06-02 7:12 ` Oliver Neukum
2006-06-02 15:11 ` Alan Stern
2006-06-02 19:49 ` David Liontooth
2006-06-01 16:59 ` Andrew Morton
2006-06-01 17:08 ` Alan Stern
2006-06-01 17:34 ` Mark Lord
2006-06-01 17:47 ` Alan Stern
[not found] <6iWP5-2gj-71@gated-at.bofh.it>
[not found] ` <6iX82-2UJ-3@gated-at.bofh.it>
2006-06-01 23:35 ` Robert Hancock
2006-06-01 23:46 ` Randy.Dunlap
[not found] <6iYGP-5hv-3@gated-at.bofh.it>
[not found] ` <6iYQx-5Jc-7@gated-at.bofh.it>
2006-06-01 23:37 ` Robert Hancock
-- strict thread matches above, loose matches on Subject: below --
2006-06-05 11:07 Lee Dowling
[not found] <6kl8h-1Uf-15@gated-at.bofh.it>
2006-06-07 0:51 ` Robert Hancock
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