C-Media / usb device bug ?

C-Media / usb device bug ?

[Pablo Yaggi]

(sorry if this come twice, i think i miss posted first one)

Hi,
 I'm working in a multi-capture application with alsa and i discovered
if i attach two "c-media usb headphone set" adapters to an usb hub which
is attached to my computer when i try to read from the two devices the
first one read (also open) errors with (-77) bad file descriptor status
and the other one keep working. When i attach the two devices directly to
the usb connectors (without hub) all works fine, the two devices can be
read at the same time. I proved Hubs version 1.0 and 2.0 .

Regards
Pablo


 This is the /proc/asound/cards when i attach them to the hub:
(yes i also have an intel device)

0 [ICH6           ]: ICH4 - Intel ICH6
                      Intel ICH6 with AD1980 at 0xd0201000, irq 20
 1 [default        ]: USB-Audio - C-Media USB Headphone Set
                      C-Media USB Headphone Set   at usb-0000:00:1d.1-1.3,
full speed
 2 [default_1      ]: USB-Audio - C-Media USB Headphone Set
                      C-Media USB Headphone Set   at usb-0000:00:1d.1-1.2,
full speed

and this is when i attach them directly to the computer:
0 [ICH6           ]: ICH4 - Intel ICH6
                      Intel ICH6 with AD1980 at 0xd0201000, irq 20
 1 [default        ]: USB-Audio - C-Media USB Headphone Set
                      C-Media USB Headphone Set   at usb-0000:00:1d.0-1,
full speed
 2 [default_1      ]: USB-Audio - C-Media USB Headphone Set
                      C-Media USB Headphone Set   at usb-0000:00:1d.3-2,
full speed

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Re: C-Media / usb device bug ?

[Clemens Ladisch]

Pablo Yaggi wrote:
>  I'm working in a multi-capture application with alsa and i discovered
> if i attach two "c-media usb headphone set" adapters to an usb hub which
> is attached to my computer when i try to read from the two devices the
> first one read (also open) errors with (-77) bad file descriptor status
> and the other one keep working. When i attach the two devices directly to
> the usb connectors (without hub) all works fine, the two devices can be
> read at the same time.

What kernel version are you using?

The EHCI transaction translator code (which is responsible for moving
audio data through an high speed hub) got a bugfix in 2.6.17, but still
artificially limits the bandwidth.  It will be rewritten in 2.6.18.


HTH
Clemens

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Re: C-Media / usb device bug ?

[Pablo Yaggi]

On Tuesday 19 September 2006 03:36, Clemens Ladisch wrote:
> Pablo Yaggi wrote:
> >  I'm working in a multi-capture application with alsa and i discovered
> > if i attach two "c-media usb headphone set" adapters to an usb hub which
> > is attached to my computer when i try to read from the two devices the
> > first one read (also open) errors with (-77) bad file descriptor status
> > and the other one keep working. When i attach the two devices directly to
> > the usb connectors (without hub) all works fine, the two devices can be
> > read at the same time.
> 
> What kernel version are you using?
> 
> The EHCI transaction translator code (which is responsible for moving
> audio data through an high speed hub) got a bugfix in 2.6.17, but still
> artificially limits the bandwidth.  It will be rewritten in 2.6.18.
> 
> 
> HTH
> Clemens
> 

I tested it on 2.6.15, 2.6.16 and 2.6.17,
so you think the problem is EHCI ?  is there anyway to check it ?
is it yet in rewriting process ? 
Thank's
Pablo

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