From mboxrd@z Thu Jan 1 00:00:00 1970 From: Florian Echtler Subject: Re: [PATCH v3][RFC] add raw video stream support for Samsung SUR40 Date: Mon, 16 Mar 2015 09:36:38 +0100 Message-ID: <55069616.6040202@butterbrot.org> References: <1423063842-6902-1-git-send-email-floe@butterbrot.org> <54DB4295.1080307@butterbrot.org> <54E1D71C.2000003@xs4all.nl> <54E7AB1E.3000401@butterbrot.org> <54E85C48.6070907@xs4all.nl> <54F98E51.8040204@butterbrot.org> <54F993ED.2060701@xs4all.nl> <54FB5715.2090103@butterbrot.org> <54FB6636.6050308@xs4all.nl> <54FD6CAD.9030600@butterbrot.org> <54FD713D.5050401@xs4all.nl> <54FDA3EA.9080006@butterbrot.org> <54FDA7E5.3010004@xs4all.nl> <5501EB0B.5020806@butterbrot.org> <5505B2C0.6090309@xs4all.nl> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="GdwvKgWWaGbQ1WjIrEu9gLWom4lQaWq1K" Return-path: In-Reply-To: <5505B2C0.6090309@xs4all.nl> Sender: linux-media-owner@vger.kernel.org To: Hans Verkuil , Mauro Carvalho Chehab Cc: Laurent Pinchart , linux-input , LMML List-Id: linux-input@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --GdwvKgWWaGbQ1WjIrEu9gLWom4lQaWq1K Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Hello Hans, On 15.03.2015 17:26, Hans Verkuil wrote: > On 03/12/2015 08:37 PM, Florian Echtler wrote: >> On 09.03.2015 15:02, Hans Verkuil wrote: >>> On 03/09/2015 02:45 PM, Florian Echtler wrote: >>>> On 09.03.2015 11:09, Hans Verkuil wrote: >>>>> The error almost certainly comes from usb_submit_urb(). That functi= on does some >>>>> checks on the sgl: >>>>> >>>> I'll do my best to track this down. Do you think this is an error in= my >>>> code, one in the USB subsystem, or some combination of both? >>> >>> If the USB core indeed requires scatter-gather segments of specific l= engths >>> (modulo max), then that explains the problems. >>> So as suggested try to see if the usb core bails out in that check an= d what the >>> 'max' value is. It looks like only XHCI allows SG segments of any siz= e, so I really >>> suspect that's the problem. But I also need to know the 'max' value t= o fully >>> understand the implications. >> >> Finally managed to confirm your suspicions on a kernel with a patched >> dev_err call at the location you mentioned: >> >> So the SG segments are expected in multiples of 512 bytes. I assume th= is >> is not something I can fix from within my driver? >=20 > No, you can't. I would use dma-sg, but disable the USERPTR support. > Also comment why USERPTR support is disabled. >=20 > This was interesting :-) >=20 Thanks again for your help, new patch is submitted. Just for my understanding: is this a hardware limitation? And why does dma-sg select such a weird segment size like 4080? Best, Florian --=20 SENT FROM MY DEC VT50 TERMINAL --GdwvKgWWaGbQ1WjIrEu9gLWom4lQaWq1K Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAlUGlhYACgkQ7CzyshGvatiPsACfVUhJlbeYWpL9of1YwJ5NPBaA RIcAoMaLytYi3213vYK6yQ44/LsMINgx =ykks -----END PGP SIGNATURE----- --GdwvKgWWaGbQ1WjIrEu9gLWom4lQaWq1K--