From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:35663 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752005AbeFFUhP (ORCPT ); Wed, 6 Jun 2018 16:37:15 -0400 Date: Wed, 6 Jun 2018 22:37:13 +0200 From: Pavel Machek To: Tomasz Figa Cc: mchehab+samsung@kernel.org, mchehab@s-opensource.com, Hans Verkuil , pali.rohar@gmail.com, sre@kernel.org, Sakari Ailus , Linux Media Mailing List , Hans Verkuil Subject: Re: [RFC, libv4l]: Make libv4l2 usable on devices with complex pipeline Message-ID: <20180606203713.GA10491@amd> References: <20180319095544.7e235a3e@vento.lan> <20180515200117.GA21673@amd> <20180515190314.2909e3be@vento.lan> <20180602210145.GB20439@amd> <20180606084612.GB18743@amd> <20180606105116.GA4328@amd> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="zYM0uCDKw75PZbzx" Content-Disposition: inline In-Reply-To: Sender: linux-media-owner@vger.kernel.org List-ID: --zYM0uCDKw75PZbzx Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi! > > Thanks for thread pointer... I may be able to get in using hangouts. > > > > Anyway, there's big difference between open("/dev/video0") and > > v4l2_open("/dev/video0"). I don't care about the first one, but yes we > > should be able to support the second one eventually. > > > > And I don't think Mauro says apps like Camorama are of open() kind. >=20 > I don't think there is much difference between open() and v4l2_open(), > since the former can be changed to the latter using LD_PRELOAD. Well, if everyone thinks opening more than one fd in v4l2_open() is okay, I can do that. Probably "if argument is regular file and has .mc extension, use open_complex"? =20 > If we simply add v4l2_open_complex() to libv4l, we would have to get > developers of the applications (regardless of whether they use open() > or v4l2_open()) to also support v4l2_open_complex(). For testing > purposes of kernel developers it would work indeed, but I wonder if it > goes anywhere beyond that. I'd like people to think "is opening multiple fds okay at this moment?" before switching to v4l2_open_complex(). But I guess I'm too caref= ul. > If all we need is some code to be able to test kernel camera drivers, > I don't think there is any big problem in adding v4l2_open_complex() > to libv4l. However, we must either ensure that either: > a) it's not going to be widely used > OR > b) it is designed well enough to cover the complex cases I mentioned > and which are likely to represent most of the hardware in the wild. =2Emc descriptors should be indeed extensible enough for that. Best regards, Pavel --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --zYM0uCDKw75PZbzx Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAlsYRfkACgkQMOfwapXb+vLmoACgvAHHS3j0GrgpnbjucLg8YuSE R60AoKnSuFFUoop6ha8ReSoQODdOniPz =3AkM -----END PGP SIGNATURE----- --zYM0uCDKw75PZbzx--