linux-kernel - Re: PROBLEM: USB ACM device does not work

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Date:	Wed, 1 Jul 2009 12:56:46 +0200
From:	Oliver Neukum <oliver@...kum.org>
To:	Arseniy Lartsev <ars3n@...dex.ru>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	USB list <linux-usb@...r.kernel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: PROBLEM: USB ACM device does not work

Am Mittwoch, 1. Juli 2009 11:01:06 schrieb Arseniy Lartsev:
> On Wednesday 01 July 2009 01:01:00 Alan Stern wrote:
> > This looks like your problem.  Low-speed devices are not allowed to
> > have bulk endpoints.  Linux internally changes them to interrupt
> > endpoints with interval = 1 and maxpacket size no larger than 8.
>
> Maybe this device is a little "buggy". But Linux should support buggy
> devices as well.

Yes, it should. We just needed to understand why it failed.


> +		ep = (usb_pipein(acm->rx_endpoint) ? acm->dev->ep_in : acm->dev->ep_out)
> +				[usb_pipeendpoint(acm->rx_endpoint)];
> +		if (usb_endpoint_xfer_int(&ep->desc))
> +			usb_fill_int_urb(rcv->urb, acm->dev,
> +					 acm->rx_endpoint,
> +					 buf->base,
> +					 acm->readsize,
> +					 acm_read_bulk, rcv, 0xff);

The patch is good except for this.
We should make sure this interval matches usbcore's value.
Would you care to redo it with that change?

	Regards
		Oliver

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