On Mon, Oct 7, 2013 at 11:13 AM, Javier Martinez Canillas <javier.martinez@xxxxxxxxxxxxxxx> wrote: > On 10/07/2013 11:06 AM, Roger Quadros wrote: >>> >>> Well that's a very good question indeed. >>> >>> The thing is that the IGEP0030 is a Computer-on-Module [1] that is used in >>> conjunction with expansion boards and some of them have USB HOST support such as >>> IGEP Paris [2] and IGEP Berlin [3]. >>> >>> Support for this expansion boards is still not in mainline but there are plans >>> to add them using Device Tree overlays [4] once/if this land on mainline. >>> >> >> Why would your boards need Device Tree overlays? From the looks of it, the configuration >> of SOM + base board don't seem to change at runtime. >> > > Indeed, a static configuration (DTS) would be enough now that I think about it. > Hi Roger, Now that I had coffee I remember why I think that even when Device Tree overlays are not strictly required for a SOM + base board it could be handy to use. If we use a static configuration (DTB) then the same firmware can't be used by any IGEP COM Module user. She would have to choose a DTB to pass to the kernel on boot. While using DT overlays the same firmware that provides a minimal DTB can be used regardless of the base board used (as long as there are all the needed fragment/overlays hooks in the DTS). After all the SOM has a NAND flash memory and a uSD/MMC slot so a minimal DTB is needed to boot and the support for all the peripherals present on the base board can be added by triggering a device tree overlay load from user-space. Or maybe I'm misunderstanding the use case for DT overlays since I had just read about it but I don't have practical experience with it. Thanks a lot and best regards, Javier -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
