On Thu, Feb 19, 2015 at 12:01:14PM -0600, Rob Herring wrote: > On Wed, Feb 18, 2015 at 8:08 PM, Frank Rowand <frowand.list@xxxxxxxxx> wrote: > > On 2/18/2015 6:59 AM, Pantelis Antoniou wrote: > >> Implement a method of applying DT quirks early in the boot sequence. > >> > >> A DT quirk is a subtree of the boot DT that can be applied to > >> a target in the base DT resulting in a modification of the live > >> tree. The format of the quirk nodes is that of a device tree overlay. > > > > The use of the word "quirk" is a different mental model for me than what > > this patch series appears to be addressing. I would suggest totally > > removing the word "quirk" from this proposal to avoid confusing the > > mental models of future generations of kernel folks. > > This comes from me as quirks are a different usecase I had in mind, > but one that could use a similar mechanism. Although, in the case of > quirks, I would expect them to be overlays built into the kernel. It > would be more a way to update old dtbs. > > > What this patch series seems to be proposing is a method to apply DT > > overlays as soon as unflatten_device_tree() completes. In other words, > > making the device tree a dynamic object, that is partially defined by > > the kernel during boot. Well, to be fair, the kernel chooses among > > several possible alternatives encoded in the DT blob. So the device > > tree is no longer a static object that describes the hardware of the > > system. It may not sound like a big deal, but it seems to me to be > > a fundamental shift in what the device tree blob is. Something that > > should be thought about carefully and not just applied as a patch to > > solve a point problem. > > I agree. I would not want to see every board for an SOC become an > overlay for example. I think it has to be limited to truly plugable > h/w (e.g. capes) or minor changes. We just have to define what is > minor. :) > Everything that isn't OIR capable but fixed at boot time. OIR can and should be handled with "real" overlays. OIR implies removal; I would assume that what is discused here is insertion-only, and runtime removal is neither required nor wanted. Or at least that is our use case. Guenter -- 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
