On Monday 14 January 2013, Vineet Gupta wrote: > > On Wednesday 07 November 2012 07:46 PM, Arnd Bergmann wrote: > > OK, I have DeviceTree infrastructure in place. After wrapping my head around > irq-domains, the whole thing indeed seems like a nice abstraction. ARC Port > converted to it and patches to arc-uart driver to that effect posted to serial > lists. Ok, very good. > Couple of things though: > > 1. While I've eliminated the platform_device population for SERIAL_ARC, we still > need the static resource definitions and aux platform data for > early_platform_add_devices() for SERIAL_ARC_CONSOLE since it uses the early param > based driver registration and device probe. AFAIKS, there's no existing way to > scan a special "earlyprintk" node (from flat tree) which at a minimum contains a > "reg" property and some device specific platform info. There are only a few other > drivers which uses the same design (e.g. tty/serial/sh-sci.c) but they don't seem > to be DT enabled. Thus in the short term we will have to live with static coding > for early platform device. Later on we can clean it up - I can take a stab at > adding earlyprintk based bits to fdt.c - if that makes sense. There is always a question of how early you want the early printk to be -- the earlier you want it, the more hacks you end up needing. The early_platform_device infrastructure is not used by a lot of architectures, so things can get a little hairy. Something you can do though is have an early_console without a platform_device attached to it, and scan the device tree for the nodes manually in order to find the registers. It would be good if we could eventually agree on a common approach for this, but right now just use whatever works for you. > 2. We really need a Documentation/dt-for-new-linux-arches.txt, as the existing > refs - while very helpful - fail to mention subtleties such as you absolutely need > a intc instance and a default irq domain ..... before the driver can start using > the DT. Also the board specific callbacks etc are not really fundamental to the DT > concept (at least I initially thought so) causing a distraction when adding the > initial implementation. The minimal dynamic device population can very well be > done in a arch initcall. I'll sum these up in a documentation-for-dummies and > float around. Ok, great! That is very much appreciated. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
