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: Thu, 12 Mar 2015 20:37:47 +0100 Message-ID: <5501EB0B.5020806@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> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="9x7UqkhdwSIhi66Pomg6H5RiHr2uT2dvs" Return-path: In-Reply-To: <54FDA7E5.3010004@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) --9x7UqkhdwSIhi66Pomg6H5RiHr2uT2dvs Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Hello Hans, 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 function= does some >>> checks on the sgl: >>> >>> I wonder it the code gets there. Perhaps a printk just before the ret= urn -EINVAL >>> might help here (also print the 'max' value). >>> >>> So you will have to debug a bit here, trying to figure out which test= in the usb >>> code causes the usb_sg_wait error. >> I'll do my best to track this down. Do you think this is an error in m= y >> code, one in the USB subsystem, or some combination of both? >=20 > If the USB core indeed requires scatter-gather segments of specific len= gths > (modulo max), then that explains the problems. > So as suggested try to see if the usb core bails out in that check and = what the > 'max' value is. It looks like only XHCI allows SG segments of any size,= so I really > suspect that's the problem. But I also need to know the 'max' value to = fully > understand the implications. Finally managed to confirm your suspicions on a kernel with a patched dev_err call at the location you mentioned: Mar 12 20:33:51 sur40 kernel: [ 1159.509580] (null): urb 0 length mismatch: length 4080, max 512 Mar 12 20:33:51 sur40 kernel: [ 1159.509592] sur40 2-1:1.0: error -22 in usb_sg_wait So the SG segments are expected in multiples of 512 bytes. I assume this is not something I can fix from within my driver? Best regards, Florian --=20 SENT FROM MY DEC VT50 TERMINAL --9x7UqkhdwSIhi66Pomg6H5RiHr2uT2dvs 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 iEYEARECAAYFAlUB6wsACgkQ7CzyshGvatgR7wCdGAW/+Y2LTdo7+0JZOTXOQaad x0MAoPZly9/i3jceXbqn9z3UjfOaFzmi =G6oY -----END PGP SIGNATURE----- --9x7UqkhdwSIhi66Pomg6H5RiHr2uT2dvs--