On 8/6/19 5:58 pm, Christian Mauderer wrote: > ----- Ursprüngliche Mail ----- >> Von: "Oyake, Amalaye (386M)" <amalaye.oy...@jpl.nasa.gov> >> An: "Chris Johns" <chr...@rtems.org>, "Vijay Kumar Banerjee" >> <vijaykumar9...@gmail.com>, "Christian Mauderer" >> <christian.maude...@embedded-brains.de> >> CC: "RTEMS Users" <users@rtems.org> >> Gesendet: Samstag, 8. Juni 2019 04:57:02 >> Betreff: Re: [EXTERNAL] Re: BeagleBone Black Networking (wifi and/or wired) > >> Device Tree overays are a method used to update the Device Tree. Given a >> device >> tree that describes all the devices, let's say you add a new SPI device, you >> can update the device tree with a (blob) device tree overlay. >> >> I should ask (without Googling), What is the Device Tree Overlay mechanism in >> RTEMS? > > > Hello Amalaye, > > as far as I know, the device tree overlay mechanism in RTEMS is not > implemented. There is the prototype of fdt_overlay_apply() in libfdt.h but > there is no implementation. So there are two methods: > > 1. Applying the overlay on a build machine. Vijay did that during his tests.
How do you do this? > 2. Use the U-Boot mechanism to apply overlays before booting RTEMS. That > should most likely work too. But I didn't test it yet. OK >> On 6/7/19, 6:17 PM, "users on behalf of Chris Johns" >> <users-boun...@rtems.org on >> behalf of chr...@rtems.org> wrote: >> >> On 8/6/19 1:53 am, Vijay Kumar Banerjee wrote: >> > >> > I would like to add that in two projects of this year( I2C and PRU-ICSS >> drivers) >> > we >> > are using our own device tree overlays that make our drivers work. >> Where to add >> > the device >> > tree related stuff seems like an important question. >> >> What are device tree overlays? > > Like Oyake already said: They are some small pices of device trees that are > just added to the base tree in it's binary form. Linux (and most likely > FreeBSD too) supports that even after boot. If you add an overlay it > re-parses the device tree, updates GPIO settings and loads new drivers. The > alternative is to let the boot loader apply them during boot. What is needed to do this? Maybe I can add it to rtems-boot-image as a way to handle this at the u-boot version. > A practical example would be adding a I2C device like a DS1338 RTC to the > extension connector of the Beagle: > https://github.com/beagleboard/bb.org-overlays/blob/master/src/arm/BB-I2C2-RTC-DS1338.dts I see the need for this. > I suggested them for Vijays GSoC project to be able to add an I2C adaption > layer so that libbsd uses the RTEMS i2c drivers. That's necessary so that > RTEMS applications can still use the RTEMS i2c interface but at the same time > the FreeBSD drivers (in that case for some chip related to HDMI) can use the > BSD interface. OK. Chris _______________________________________________ users mailing list users@rtems.org http://lists.rtems.org/mailman/listinfo/users
