From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomi Valkeinen Subject: Re: [PATCH V7 11/12] Documentation: bridge: Add documentation for ps8622 DT properties Date: Wed, 24 Sep 2014 12:08:37 +0300 Message-ID: <54228A15.4090901@ti.com> References: <1409150399-12534-1-git-send-email-ajaykumar.rs@samsung.com> <5419760A.7020908@ti.com> <20140922075424.GB1470@ulmo> <54202C86.3040808@ti.com> <20140923062111.GE30514@ulmo> <54213DAC.5010806@ti.com> <20140923095314.GS30514@ulmo> <542160DF.2040008@ti.com> <20140923145833.GI5982@ulmo> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="NbGcMAWJWkihmncc2QFXaKmI1wS2lSDIi" Return-path: In-Reply-To: <20140923145833.GI5982@ulmo> Sender: linux-samsung-soc-owner@vger.kernel.org To: Thierry Reding Cc: Ajay Kumar , dri-devel@lists.freedesktop.org, linux-samsung-soc@vger.kernel.org, devicetree@vger.kernel.org, inki.dae@samsung.com, robdclark@gmail.com, daniel.vetter@ffwll.ch, seanpaul@google.com, ajaynumb@gmail.com, jg1.han@samsung.com, joshi@samsung.com, prashanth.g@samsung.com, Laurent Pinchart List-Id: devicetree@vger.kernel.org --NbGcMAWJWkihmncc2QFXaKmI1wS2lSDIi Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable On 23/09/14 17:58, Thierry Reding wrote: >> But if a panel driver controls its video source, it makes sense for th= e >> panel driver to get its video source in its probe, and that happens >> easiest if the panel has a link to the video source. >=20 > That's an orthogonal problem. You speak about the link in software here= , > whereas the phandles only represent the link in the description of > hardware. Now DT describes hardware from the perspective of the CPU, so= > it's sort of like a cave that you're trying to explore. You start at th= e > top with the address bus, from where a couple of tunnels lead to the > various peripherals on the address bus. A display controller might have= > another tunnel to a panel, etc. We don't do that for GPIOs, regulators, etc. either. And for video data there are no address buses. Yes, for DSI and similar we have a control bus, but that is modeled differently than the video data path. Now, I'm fine with starting from the CPU, going outwards. I agree that it's probably better to model it in the direction of the data stream, even if that would make the SW a bit more complex. However, I do think it's not as clear as you make it sound, especially if we take cameras/sensors into account as Laurent explained elsewhere in this thread. > If you go the other way around, how do you detect how things connect? > Where do you get the information about the panel so you can trace back > to the origin? When the panel driver probes, it registers itself as a panel and gets its video source. Similarly a bridge in between gets its video source, which often would be the SoC, i.e. the origin. Tomi --NbGcMAWJWkihmncc2QFXaKmI1wS2lSDIi 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 iQIcBAEBAgAGBQJUIooVAAoJEPo9qoy8lh71Zl0P/2siTDSQiaqPObwTDpVR2bn+ +wvaFqk/LtFJxeDxptVvGBJLI7KPlMhe/XqH7mpJr4oBGML16o750m7SJPsh+d6V 5uvdxCS5fEA+JgZQwAfuz1PI1tOsLEgGnWtVZeup8K45Sis8JP7ioXOGnR2hobV9 jbyl9GYWS7DwnvFPEHwsGnuayDXgKHIQHkBbGSMvxOGjxpq9ZbKUBKbqyow/epi7 46C8vOHqnjm7QiijMHtDXYsC1EoW4zekm63ljVRJxp4wn4PXuOKOrGFHe6zaDICs 4eFiwr5Q6KuZa9FdHWwjnwHHVSiJShyzAkb6Z9hysJDeVAxp4UOMreg2NZbW9YFc skDzvN0eQLPHkzyX+dcxqtntbExYY2JG7sot/6wGxCSS7wlJ2X0PnoO0OeVGeafT BD01plzEDasQQeTYATWQXd2tGHHdemaXnhrBoPhAJY4a59lKER62zyJkYN4s7oe7 Dpa8g9LzEyt3PDBAZFLhJNlcCIUupGhrsHeYSwsD3mpHQ/Gu+Kqz16g/hPGVfxvL v593x9TS/9XrGNAvKirX/cVoNwrbP0rySjmoqSrbGlGMtWn060AHSrv71u/pMpDC z28rO2PyJUFD05LCbyJzgWgARXEao0wH5F30ejFtae6Ue7ZgiuaVKgBhcKh/vpn/ g/Br1ifyBLswH5n1dNQr =EUl1 -----END PGP SIGNATURE----- --NbGcMAWJWkihmncc2QFXaKmI1wS2lSDIi--