Hi Lee, On Jan 8, 2013, at 12:00 PM, Lee Jones wrote:
>>>>> At the end of the line, some kind of hardware glue is going to be needed. >>>>> >>>>> I just feel that drawing from a sample size of 1 (maybe 2 if I get to >>>>> throw >>>>> in the beagleboard), it is a bit premature to think about making it overly >>>>> general, besides the part that are obviously part of the infrastructure >>>>> (like the DT overlay stuff). >>>>> >>>>> What I'm getting at, is that we need some user experience about this, >>>>> before >>>>> going away and creating structure out of possible misconception about the >>>>> uses. >>>> >>>> IMHO stuff like this will be needed by many SoCs. Some examples of similar >>>> things for omaps that have eventually become generic frameworks have been >>>> the clock framework, USB OTG support, runtime PM, pinmux framework and >>>> so on. >>>> >>>> So I suggest a minimal generic API from the start as that will make things >>>> a lot easier in the long run. >>> >>> I agree. The ux500 platform already has the concept of "user interface >>> boards", >>> which currently is not well integrated into devicetree. I believe Sascha >>> mentioned that Pengutronix had been shipping some other systems with add-on >>> boards and generating device tree binaries from source for each combination. >>> >>> Ideally, both of the above should be able to use the same DT overlay logic >>> as BeagleBone, and I'm sure there are more of those. >> >> Hmm, I see. >> >> I will need some more information about the interface of the 'user interface >> boards'. >> I.e. how is the board identified, what is typically present on those boards, >> etc. > > User Interface Boards are mearly removable PCBs which are interchangeable > amongst various hardware platforms. They are connected via numerous > connectors which carry all sorts of different data links; i2c, spi, rs232, > etc. The UIB I'm looking at right now has a touchscreen, speakers, a key > pad, leds, jumpers, switches and a bunch of sensors. > > You can find a small example of how we interface to these by viewing > 'arch/arm/boot/dts/stuib.dtsi'. To add a UIB to a particular build, we > currently include it as a *.dtsi from a platform's dts file. I see. What I'm asking about is whether there's a method where you can read an EEPROM, or some GPIO code combination where I can find out what kind of board is plugged each time. If there is not, there is no way to automatically load the overlays; you can always use the kernel command line, or have the a user space application to request the loading of a specific board's overlay. Regards -- Pantelis > >> Can we get some input by the owner of other similar hardware? I know the FPGA >> people have similar requirements for example. There are other people that >> are hitting >> problems getting DT to work with their systems, like the V4L people with the >> order >> of initialization; see http://lwn.net/Articles/531068/. I think the V4L >> problem is >> cleanly solved by the overlay being contained in the V4L device node and >> applied just before >> the device is probed. >> >> In the meantime it would be better to wait until we have some ack from the >> maintainers >> of the core subsystems about what they think. >> >> Regards >> >> -- Pantelis >> > > -- > Lee Jones > Linaro ST-Ericsson Landing Team Lead > Linaro.org │ Open source software for ARM SoCs > Follow Linaro: Facebook | Twitter | Blog -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
