On Thu, Apr 28, 2016 at 9:27 AM, Felipe Balbi <balbi@xxxxxxxxxx> wrote: > > Hi, > > Arnd Bergmann <arnd@xxxxxxxx> writes: >> On Thursday 28 April 2016 15:16:12 Russell King - ARM Linux wrote: >>> On Thu, Apr 28, 2016 at 09:37:08AM +0300, Felipe Balbi wrote: >>> > >>> > Hi, >>> > >>> > Arnd Bergmann <arnd@xxxxxxxx> writes: >>> > > pointer and pass that in platform_data. This is really easy, it's >>> > >>> > Sorry but passing a struct device pointer in platform_data is >>> > ridiculous. Not to mention that, as I said before, we can't assume which >>> > device to pass to xhci_plat in the first place. It might be dwc->dev and >>> > it might be dwc->dev->parent. >>> >>> +1. Passing an unref-counted struct device through platform data is >>> totally mad, Arnd you're off your rocker if you think that's a good >>> idea. What's more is that there's no way to properly refcount the >>> thing. >> >> It's the parent device (or NULL), there is no way it can ever go away as >> it's already refcounted through the device subsystem by the creation >> of the child device. > > you're assuming that based on what we have today. We could get into a > situation where we need to use a completely unrelated device and the > problem exists again. > >> I do realize that it's a hack, but the idea is to get rid of that >> as soon as possibly by fixing the way the xhci device is probe so >> we no longer need to fake a platform_device as the child here and >> can just use the device itself. > > okay, let me try to be extra clear here: > > We will *not* remove the extra platform_device because it actually > *does* exist and helps me hide/abstract a bunch of details and make > assumptions about order of certain events. We have already gone through > that in the past when I explained why I wrote dwc3 the way it is; if you > need a refresher, there are mailing list archives for that. > > Moreover, this same problem exists for anything under drivers/mfd. It > just so happens that they're usually some i2c or spi device which don't > do DMA by themselves. Hi Felipe and Arnd, It has been a while since the last response to this discussion, but we haven't reached an agreement yet! Can we get to a conclusion on if it is valid to create child platform device for abstraction purpose? If yes, can this child device do DMA by itself? - Leo -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
