Bug#308098: acknowledged by developer (Re: Bug#308098: libsane: fail my canon N650U on USB hub, works fine without the hub)

2005-05-08 Thread Jean-Louis MOUNIER 




Debian Bug Tracking System a écrit :

  This is an automatic notification regarding your Bug report
#308098: libsane: fail my canon N650U on USB hub, works fine without the hub,
which was filed against the libsane package.

It has been closed by one of the developers, namely
Julien BLACHE <[EMAIL PROTECTED]>.

Their explanation is attached below.  If this explanation is
unsatisfactory and you have not received a better one in a separate
message then please contact the developer, by replying to this email.

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Subject: Re: Bug#308098: libsane: fail my canon N650U on USB hub, works fine
 without the hub
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From: Julien BLACHE <[EMAIL PROTECTED]>
Date: Sun, 08 May 2005 10:14:48 +0200
In-Reply-To: <[EMAIL PROTECTED]> (Jean-Louis Mounier's message
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Jean-Louis Mounier <[EMAIL PROTECTED]> wrote:

  
  
The scanner works fine when plugged directly on the PC, it fails when using a
USB HUB betwwen the scanner and the PC. I get a device IO error.
with "cat /proc/bus/usb/devices", I get "driver=none" for the scanner.

  
  
Then the USB hub you use is the problem. Simple, really.

If your scanner is bus-powered, and your USB hub didn't come with an
AC adapter of its own, then your scanner can't get enough power from
the USB bus and there's nothing the software can do to get it to work.

Get an AC adapter for your hub if possible, or get one for the
scanner if possible, or get another, less crappy, USB hub.

JB.

  

Bonjour Julien,

Sorry folk, it was late and I didn't realize that the power consumption
of the hub is 100mA and the hub uses 500mA . So the hub needed to be
self powered (the scanner doesn't have power supply, which is very
practical). After plugging the hub power supply, all works fine.

The bug can be closed.

The main lesson would be to improve error detection on USB, the scanner
was detected by sane-find-scanner but was not usable, that is what made
me submit this (my first ) bug report.
.
Thank you

Bug#308098: acknowledged by developer (Re: Bug#308098: libsane: fail my canon N650U on USB hub, works fine without the hub)

2005-05-08 Thread Julien BLACHE 
Jean-Louis MOUNIER <[EMAIL PROTECTED]> wrote:

> Sorry folk, it was late and I didn't realize that the power
> consumption of the hub is 100mA and the hub uses 500mA . So the hub
> needed to be self powered (the scanner doesn't have power supply,
> which is very practical). After plugging the hub power supply, all
> works fine.

When it's not a power issue, it's a bandwidth issue... USB hubs are
evil.

> The main lesson would be to improve error detection on USB, the
> scanner was detected by sane-find-scanner but was not usable, that is
> what made me submit this (my first ) bug report.

There's not much that can be done in this regard, unfortunately :(

JB.

-- 
 Julien BLACHE - Debian & GNU/Linux Developer - <[EMAIL PROTECTED]> 
 
 Public key available on  - KeyID: F5D6 5169 
 GPG Fingerprint : 935A 79F1 C8B3 3521 FD62 7CC7 CD61 4FD7 F5D6 5169 


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