On Tue, Oct 02, 2018 at 01:47:33PM -0300, Rodrigo Exterckötter Tjäder wrote: > > > > > About device tree overlays, I read overlay-notes.txt, but I went > > > > > looking for an example with "git grep /plugin/ arch" and it came > > > > > empty. Is this approach not used for other boards? > > > > > > > > It is, it's simply not stored in the kernel, but through other third > > > > party repos. > > > > > > So that would mean that it's up to every distro to support the boards > > > instead of relying on mainline support? > > > > Distros would have to integrate it either way. One would need to > > detect and / or ask for the board variant in order to load say the BT > > stack, or to know if you want to boot from the eMMC or from the SD > > card. > > Yeah, but now if a bug is found in the device tree it has to be fixed > once per distro instead of only on mainline. Yeah, well, I never said it was perfect. > > > > > Does the overlay approach make the device available at boot time? That > > > > > is important for a storage device such as eMMC. > > > > > > > > > > I went with the separate dts approach because that's what I saw was > > > > > done for other similar cases, like Pine64 and Pine64+, OLinuXino-LIME2 > > > > > and its variant with eMMC, among others. > > > > > > > > Yeah, but in all these cases, it was done from day one, not after the > > > > facts. > > > > > > For the LIME2 the dts for the emmc variant was commited two years > > > after the base LIME2 dts. > > > > > > What if instead of keeping the current dt for the least featureful > > > model we keep it for the most featureful model and create new dts for > > > the two less featureful models? > > > > This is a different story though. The LIME2 eMMC variant was created > > way after the original LIME2, with a separate name. > > What about the idea of keeping the current dt for the most featureful > variant and creating new dts for the other two? > > That would make it so that no one's device stops working and would > have mailine support for all three devices. IIRC that has been the first introduced version, so that would make sense. Chen-Yu, any opinion? > Also, the current device tree doesn't represent any existing device: > it has wifi on but no emmc. That variation does not exist. Most of our device tree are far from complete, so you shouldn't treat them as such. Maxime -- Maxime Ripard, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
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