From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thierry Reding Subject: Re: ARM topic: Is DT on ARM the solution, or is there something better? Date: Mon, 18 Nov 2013 17:18:14 +0100 Message-ID: <20131118161812.GP26046@ulmo.nvidia.com> References: <20131020231134.GR25034@n2100.arm.linux.org.uk> <20131021083242.GB30088@pengutronix.de> <20131021084854.GV25034@n2100.arm.linux.org.uk> <20131021092730.GF30088@pengutronix.de> <20131024072811.GS30088@pengutronix.de> <20131118124518.GA16735@n2100.arm.linux.org.uk> <20131118153750.GM26046@ulmo.nvidia.com> <20131118161151.GG16735@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="NDuspjMMC1Ui5ypn" Return-path: Content-Disposition: inline In-Reply-To: <20131118161151.GG16735-l+eeeJia6m9vn6HldHNs0ANdhmdF6hFW@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Russell King - ARM Linux Cc: Rob Clark , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "ksummit-2013-discuss-cunTk1MwBs98uUxBSJOaYoYkZiVZrdSR2LY78lusg7I@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , Stephen Warren List-Id: devicetree@vger.kernel.org --NDuspjMMC1Ui5ypn Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Nov 18, 2013 at 04:11:51PM +0000, Russell King - ARM Linux wrote: > On Mon, Nov 18, 2013 at 04:37:51PM +0100, Thierry Reding wrote: > > Very nice. This is in fact very similar to a skeleton I started to > > implement locally. The names vary to some degree, but the general > > approach is the same. > >=20 > > This also happens to be very similar to what Tegra DRM does, just as a > > set of helpers rather than a bus type. I like it a lot. > >=20 > > In particular this gives every driver a good amount of flexibility to > > implement the matching in a way that's appropriate. On hardware where > > the relationships are hierarchical, a driver can use that to its > > advantage. Whenever that's not possible it can be done using phandles > > or any other meta data that fits the particular use-case. >=20 > Indeed - I set out to solve the following problems: >=20 > - How do we deal with a componentised device such that we can find all > of its component devices, and know when we have them all? > - How can we probe the master device when we know we have all the > components? > - How do we tear down the master device when one of the components is > removed? >=20 > I intentionally didn't want the code to answer the question about how > we specify how the components are organised - that's a subject best > left to the subsystem and/or device, since it's something which will > most likely vary. >=20 > > Do you have a branch somewhere that I could use to test this with? >=20 > Not yet - and there probably won't be, because the code itself is not > large - it's currently less than 500 lines. >=20 > The code has evolved over time - with imx-drm as a guinea pig. >=20 > The code which I have so far committed (and some people are using in > patch form on the carrier-1 boards) is an earlier version, which just > caters for proper init ordering and making it possible to unbind the > "master" device. It gets that init ordering by using deferred probing > if there's no connectors, or the CRTCs which the connectors refer to > are missing - it needs no changes to the DT representation. >=20 > Since then, I've augmented it as I described and that's currently just > as an additional patch on top which adds the master device idea - which > does need those additional changes. >=20 > Logically, it can't stay as two separate patches, because it won't be > possible to "migrate" to it in stages. So I'm fully intending to > squash that all down to one patch which adds the core code (probably > ultimately into drivers/base). >=20 > IOW, watch this space this week. :) Will do! Thanks for doing this. Thierry --NDuspjMMC1Ui5ypn Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQIcBAEBAgAGBQJSij3EAAoJEN0jrNd/PrOh34kP/3uDAHzQM3DlSapjS223nhr0 0n9UwMGUgR6UM79wLZ0FMz2W/JyHWsRmMLeI2TBa92pI0PU/7W7MEvGF2KY/txKT Ah6FoG7BpgR78wnxagtvYECs4BvS4ax/eB5+lz7LISLtJKoTKi2fvT/4e/WIcZ/3 tS2sQ7M5CfCuz+L4ZShP9OCM7YjAz0Nl6xuV8AHD4zUPNv+yk4rndzCxOEkgGF+u aWDRO/n2rMP0Sh+fJ0A4OtB+YRGkuGjyDA72qqqwml9oV6hOzsPEXntfPP7Ccro2 JMHTAif5qxbAwCuTio2cKs/kR20lLHcNJibOyQgEperUo8el0yT+I8+4EuaXAlo3 AoOSELEONVPT5s6SH+icY+92Zj/hT6cWknXD3fjY/g77TOYhUHlLTQo3sZrr83h7 oXDkmIix4oxfAX2oOErWPjlMgWPT2XIRdhlwamarSCHdky+MqM0VThZGBBPwjIMz rxQjq9AQFF3m7yNHVmUY2+klyAHxvPutu555Sh5HZxH2wGzTGMfMqUW8n7UP4bcs 83JEnDvyXB40USpIo7DKKix2qQqmtTHsh+Rl26sVFkQT9CJqXFrrgTp/mcs7PXcl pgHJo5HDxHryUsEx3cYIKViqfLlpr3ITUTr6jYGByzVmO7gYk+6wlT2tnn+iDaKN aO/QVlkY7IFP9OAgcFIh =ElIk -----END PGP SIGNATURE----- --NDuspjMMC1Ui5ypn-- -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html