On Mon, Dec 05, 2016 at 05:59:08PM -0600, Rob Herring wrote: > On Thu, Dec 01, 2016 at 09:24:50AM -0800, Brian Norris wrote: > > Hi Benjamin and Rob, > > > > On Thu, Dec 01, 2016 at 03:34:34PM +0100, Benjamin Tissoires wrote: > > > On Nov 30 2016 or thereabouts, Brian Norris wrote: > > > > From: Caesar Wang <wxt@xxxxxxxxxxxxxx> > > > > > > > > Add a compatible string and regulator property for Wacom W9103 > > > > digitizer. Its VDD supply may need to be enabled before using it. > > > > > > > > Signed-off-by: Caesar Wang <wxt@xxxxxxxxxxxxxx> > > > > Cc: Rob Herring <robh+dt@xxxxxxxxxx> > > > > Cc: Jiri Kosina <jikos@xxxxxxxxxx> > > > > Cc: linux-input@xxxxxxxxxxxxxxx > > > > Signed-off-by: Brian Norris <briannorris@xxxxxxxxxxxx> > > > > --- > > > > v1 was a few months back. I finally got around to rewriting it based on > > > > DT binding feedback. > > > > > > > > v2: > > > > * add compatible property for wacom > > > > * name the regulator property specifically (VDD) > > > > > > > > Documentation/devicetree/bindings/input/hid-over-i2c.txt | 6 +++++- > > > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/Documentation/devicetree/bindings/input/hid-over-i2c.txt b/Documentation/devicetree/bindings/input/hid-over-i2c.txt > > > > index 488edcb264c4..eb98054e60c9 100644 > > > > --- a/Documentation/devicetree/bindings/input/hid-over-i2c.txt > > > > +++ b/Documentation/devicetree/bindings/input/hid-over-i2c.txt > > > > @@ -11,12 +11,16 @@ If this binding is used, the kernel module i2c-hid will handle the communication > > > > with the device and the generic hid core layer will handle the protocol. > > > > > > > > Required properties: > > > > -- compatible: must be "hid-over-i2c" > > > > +- compatible: must be "hid-over-i2c", or a device-specific string like: > > > > + * "wacom,w9013" > > > > > > NACK on this one. > > > > > > After re-reading the v1 submission I realized Rob asked for this change, > > > but I strongly disagree. > > > > > > HID over I2C is a generic protocol, in the same way HID over USB is. We > > > can not start adding device specifics here, this is opening the can of > > > worms. If the device is a HID one, nothing else should matter. The rest > > > (description of the device, name, etc...) is all provided by the > > > protocol. > > > > I should have spoken up when Rob made the suggestion, because I more or > > less agree with Benjamin here. I don't really see why this needs to have > > a specialized compatible string, as the property is still fairly > > generic, and the entire device handling is via a generic protocol. The > > fact that we manage its power via a regulator is not very > > device-specific. > > It doesn't matter that the protocol is generic. The device attached and > the implementation is not. Implementations have been known to have > bugs/quirks (generally speaking, not HID over I2C in particular). There > are also things outside the scope of what is 'hid-over-i2c' like what's > needed to power-on the device which this patch clearly show. > > This is no different than a panel attached via LVDS, eDP, etc., or > USB/PCIe device hard-wired on a board. They all use standard protocols > and all need additional data to describe them. Of course, adding a > single property for a delay would not be a big deal, but it's never > ending. Next you need multiple supplies, GPIO controls, mutiple > delays... This has been discussed to death already. As Thierry Reding > said, you're not special[1]. > > Now if you want to make 'hid-over-i2c' a fallback to 'wacom,w9013', I'm > fine with that. So if I understand it correctly the only change is to have DTS specify compatible = "wacom,w9013", "hid-over-i2c"; and no actual changes to the driver itself with regard to the new compatible string, correct? I wonder what, besides breaking module autoload, this really buys us? Thanks. -- Dmitry -- 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
