linux-kernel - dvb-usb stack-memory used for URB-buffers (was: Re: Problem with VMAP

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Message-ID: <20161005094036.3ffa11b5@vdr>
Date:   Wed, 5 Oct 2016 09:40:36 +0200
From:   Patrick Boettcher <patrick.boettcher@...teo.de>
To:     Jiri Kosina <jikos@...nel.org>
Cc:     Jörg Otte <jrg.otte@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Michael Krufky <mkrufky@...uxtv.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org
Subject: dvb-usb stack-memory used for URB-buffers (was: Re: Problem with
 VMAP_STACK=y)

Hi,

On Tue, 4 Oct 2016 15:26:28 +0200 (CEST)
Jiri Kosina <jikos@...nel.org> wrote:

> On Tue, 4 Oct 2016, Jörg Otte wrote:
> 
> > With kernel 4.8.0-01558-g21f54dd I get thousands of
> > "dvb-usb: bulk message failed: -11 (1/0)"
> > messages in the logs and the DVB adapter is not working.
> > 
> > It tourned out the new config option VMAP_STACK=y (which is the
> > default) is the culprit.
> > No problems for me with VMAP_STACK=n.  
> 
> I'd guess that this is EAGAIN coming from usb_hcd_map_urb_for_dma()
> as the DVB driver is trying to perform on-stack DMA.

I really thought that this youngster-mistake of mien (these
drivers+framework date from 2004-2006 and there it worked just fine)
had been fixed some years ago. 

Seems not the be the case :-(.

However, I'm happy to see people using these devices now. Even
though I don't have them anymore (or never had them in the first place).

Mauro, could you please bring me up to speed or remind when and
where you did changes in this regard? I got a little bit rusty
regarding linux-media, but I'd be happy to help.

regards,
-- 
Patrick.