Hi, On Mon, Oct 05, 2015 at 05:18:33PM +0100, Mark Brown wrote: > On Mon, Oct 05, 2015 at 10:15:11AM -0500, Felipe Balbi wrote: > > On Sun, Oct 04, 2015 at 11:55:06PM +0100, Mark Brown wrote: > > > > The trouble is getting traction on adoption. Vendors have a habit of doing > > > things like finding problems and rather than reporting them deciding that the > > > open source solution isn't great and going and writing their own thing > > > (especially when they're in stealth mode) rather than talking to anyone. > > > Sometimes we manage to avoid that but it can be challenging, and often we only > > > even hear about the new thing after it's shipping and there's a lot of inertia > > > behind changing it. The kernel ABIs tend to be a lot sticker than userspace > > > things here. > > > but this is not a solid enough argument to push anything into the kernel. > > To my mind it is a concern when considering design - it's not the only > consideration certainly but it should influence if or how we split > things. sure > > > > the same thing will happen with Type-C and power delivery. There won't be tuning > > > > to taste, of course :-) But there will be "very different ideas what what you > > > > want to do with" your charging methodology. > > > > Are those very different things about the use cases ("don't bother with > > > high speed data, get all the power you can" or whatever) or are they > > > about the details of the board? > > > I'm pretty sure there will be interesting designs in the market. I'm pretty sure > > there will be type-C systems which won't support USB 3.1 for example, even > > though they'll support USB Power Delivery in its entirety. > > That's sounding like generic USB stuff to me. > > > > Yes, definitely - my experience both in terms of watching how people > > > like handset vendors often work internally and in terms of getting > > > things adopted is that it's a lot easier if you can have one component > > > you need to update to handle new hardware rather than multiple ones that > > > need to be upgraded for things that are purely board differences. > > > IMO, just because you have it in the kernel, it doesn't mean it'll be > > adopted. Look at pm_runtime, for example; it's a very nice API and, yet, not > > used by Android (or has that changed ?) > > That's always been a bit of a myth - most Android systems use runtime PM > extensively when they're running, the discussion is really about the > edge case where you're idling the system. The Android suspend behaviour > is about the system idle case and is as much about providing a simple > way to go into an idle state, especially bearing in mind that they have > apps installed from the app store there, as anything else. It's the > making sure things are idle part of things that's different. okay > > > > okay, this is a fair point :-) I just don't see, as of now at least, how we can > > > > get to that in a way that's somewhat future-proof. It seems like we will > > > > add more and more notifications until we can't maintain this anymore. > > > > So we need to look at the new/upcoming USB specs and understand the > > > not upcoming, it's already out there. > > I assume there's ongoing work on further revisions to the spec though? that'd be a correct assumption > > > Does the problem not get easier if we break it down to just the charger > > > elements and realise that the USB C modes are going to have a lot more > > > policy in them? > > > the thing with USB C is that it's not only for negotiating a charging power > > (with power delivery you're not necessarily tied to 5V, btw), that very stack > > will also be used to change to other alternate modes, and those can be anything: > > Thunderbolt, PCIe, DisplayPort, etc. > > Surely these features have sufficient orthogonality to allow us to split > things up and deal with some of the problems while providing spaces for > future work? yeah, might. As long as we keep that voice in our heads that things are likely to change. -- balbi
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