On Tue, Mar 26, 2013 at 04:16:10PM +0000, Grant Likely wrote: > On Tue, 8 Jan 2013 12:10:20 +0200, Pantelis Antoniou <panto@xxxxxxxxxxxxxxxxxxxxxxx> wrote: > > 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. > > > > In this case the best thing to do is announce the availability of the > expansion via a request_firmware() call and let udev handle supplying > the correct overlay file. The code to load firmware files was recently removed from udev, now that the kernel handles this automatically itself :) But yes, the same call still applies, request_firmware() should work fine here. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
