Hi Sylwester On Fri, 5 Oct 2012, Sylwester Nawrocki wrote: > On 10/05/2012 12:58 PM, Guennadi Liakhovetski wrote: > >> One area that I do not yet completely understand is the i2c bus notifications > >> (or asynchronous loading of i2c modules). > >> > >> I would have expected that using OF the i2c devices are still initialized > >> before the host/bridge driver is initialized. But I gather that's not the > >> case? > > > > No, it's not. I'm not sure, whether it depends on the order of devices in > > the .dts, but, I think, it's better to not have to mandate a certain order > > and I also seem to have seen devices being registered in different order > > with the same DT, but I'm not 100% sure about that. > > The device instantiation (and initialization) order is not something that > is supposed to be ensured by a specific device tree source layout, IIUC. > The initialization sequence is probably something that is specific to a > particular operating system. I checked the device tree compiler but couldn't > find if it is free to reorder anything when converting from the human > readable device tree to its binary representation. > > The deferred probing was introduced in Linux to resolve resource > inter-dependencies in case of FDT based booting AFAIK. > > >> If this deferred probing is a general problem, then I think we need a general > >> solution as well that's part of the v4l2 core. > > > > That can be done, perhaps. But we can do it as a next step. As soon as > > we're happy with the OF implementation as such, we can commit that, > > possibly leaving soc-camera patches out for now, then we can think where > > to put async I2C handling. > > I would really like to see more than one user until we add any core code. > No that it couldn't be changed afterwards, but it would be nice to ensure > the concepts are right and proven in real life. Unfortunately I don't have any more systems on which I could easily enough try this. I've got a beagleboard with a camera, but I don't think I'm a particularly good candidate for implementing DT support for OMAP3 camera drivers;-) Apart from that I've only got soc-camera based systems, of which none are _really_ DT-ready... At best I could try an i.MX31 based board, but that doesn't have a very well developed .dts and that would be soc-camera too anyway. Thanks Guennadi --- Guennadi Liakhovetski, Ph.D. Freelance Open-Source Software Developer http://www.open-technology.de/ -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
