linux-kernel - PROBLEM: USB keyboards works only 4 per PC host port

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Date:	Fri, 8 Aug 2008 07:02:24 +0100
From:	Aivils Stoss <aivils@...net.lv>
To:	linux-input@...r.kernel.org, jkosina@...e.cz,
	linux-kernel@...r.kernel.org,
	linuxconsole-dev@...ts.sourceforge.net
Subject: PROBLEM: USB keyboards works only 4 per PC host port

Hello All!

PROBLEM: USB keyboards works only 4 per PC host port.

I work for project which will use 15 - 25 keyboards for children teaching.
I discover current Linux 2.6.22 , 2.6.24, 2.6.26 dot not support more
than 4 keyboards per single PC host port. All plugged in keyboards
are listed as USB devices, listed as input devices, but capable to
send input events are only 4 keyboards, no matter where keyboards
are plugged in to HUB cascade. All plugged in keyboards switch LED's,
when i press NumLock.

I tested various usb-hub units and various host PC hardware, i even
replace hub power supplay units from 5V1A to 5V3A. All tested cases
give best results - 4 keyboards per PC host port and worstest - some PC
cannot do more than 8 keyboards at all.
I suppose this is Linux kernel bug because i test keyboards under
Windows, which support any schema of cascading of usb hubs.

I will send any log file if that is necessary, but trouble will pop up
in a row of kernels. 2.6.22 didn't have error messages. 2.6.24, 2.6.26
tend to total slow down with eternal reset messages:
Jul 25 07:16:00 awork kernel: input,hiddev97: USB HID v1.10 Mouse 
[USB-compliant keyboard] on usb-0000:00:1d.0-1.1.2
Jul 25 07:16:01 awork kernel: usb 2-1.1.1: reset low speed USB device using 
uhci_hcd and address 17
Jul 25 07:16:01 awork kernel: usb 2-1.1.2: reset low speed USB device using 
uhci_hcd and address 18
Jul 25 07:16:02 awork kernel: usb 2-1.1.1: reset low speed USB device using 
uhci_hcd and address 17

Best regards,
Aivils Stoss
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