linux-kernel - Re: [PATCH 2/2] HID: hid-logitech-dj, querying

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Message-ID: <alpine.LNX.2.00.1308051516181.17512@pobox.suse.cz>
Date:	Mon, 5 Aug 2013 15:22:13 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Benjamin Tissoires <benjamin.tissoires@...il.com>
Cc:	Nestor Lopez Casado <nlopezcasad@...itech.com>,
	Andrew de los Reyes <adlr@...omium.org>,
	joseph.salisbury@...onical.com,
	linux-input <linux-input@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] HID: hid-logitech-dj, querying_devices was never
 set

On Fri, 2 Aug 2013, Benjamin Tissoires wrote:

> > Could you please elaborate? (and put an elaborate description to revert
> > commit log perhaps?)
> 
> Sure, so here is the revert commit log:
> 
> --
> 
> Commit "HID: hid-logitech-dj, querying_devices was never set" activate
> a flag which guarantees that we do not ask the receiver for too many
> enumeration. When the flag is set, each following enumeration call is
> discarded (the usb request is not forwarded to the receiver). The flag
> is then released when the driver receive a pairing information event,
> which normally follows the enumeration request.
> However, the USB3 bug makes the driver think the enumeration request
> has been forwarded to the receiver. However, it is actually not the
> case because the USB stack returns -EPIPE. So, when a new unknown
> device appears, the workaround consisting in asking for a new
> enumeration is not working anymore: this new enumeration is discarded
> because of the flag, which is never reset.
> 
> A solution could be to trigger a timeout before releasing it, but for
> now, let's just revert the patch.
> 
> --

Thanks Benjamin.

I'd like to have a bit more clarification about the USB3 bug, as this 
whole issue is not completely clear to me.

To be more specific -- when exactly do we receive -EPIPE, why do we 
receive it and why do we not handle it properly?

Thanks again,

-- 
Jiri Kosina
SUSE Labs
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