On 2017-04-19 11:17, Philipp Zabel wrote: > On Tue, 2017-04-18 at 15:36 +0200, Peter Rosin wrote: >> If I got things wrong when I skimmed whatever I came across, and if the >> mmio register is the only mux control option in the stars, it becomes >> less obvious... It's of course still possible to hook into the mux >> subsystem, but the benefit is questionable. And you do get the extra >> device tree node. You could of course also implement a mux driver >> outside of drivers/mux and thus make use of the mux api, but it's tiny >> and any benefit is truly small. > > What I wondered mostly is whether it would be a good idea to move the > OF-graph ports into the mux controller node, and let the video capture > device be the consumer of the mux. > But this wouldn't fit well with the clear split between the mux > controller and the actual mux hardware in the mux DT bindings. I have tried to do something similar. I think. The current drivers/i2c/muxes/i2c-mux-gpio.c is a good candidate for the same thing IIUC. That dedicated driver and the general purpose i2c mux driver does pretty much the same thing with these two DT snippets: Dedicated i2c-mux-gpio DT snippet: i2c-mux { compatible = "i2c-mux-gpio"; i2c-parent = <&i2c1>; mux-gpios = <&gpio1 22 0 &gpio1 23 0>; #address-cells = <1>; #size-cells = <0>; i2c@1 { ... }; i2c@3 { ... }; }; General purpose mux DT snippet: mux: mux-controller { compatible = "gpio-mux"; #mux-control-cells = <0>; mux-gpios = <&gpio1 22 0 &gpio1 23 0>; }; i2c-mux { compatible = "i2c-mux"; i2c-parent = <&i2c1>; mux-controls = <&mux>; #address-cells = <1>; #size-cells = <0>; i2c@1 { ... }; i2c@3 { ... }; }; I would love to find a way to cleanly get the mux framework to handle the first DT as well, and thus being able to obsolete the dedicated i2c-mux-gpio driver. I have not figured out how to accomplish that without abusing the driver-model to a point that it's not working. Help with that task is dearly appreciated. What I have stumbled on, I think, is that two drivers needs to be instantiated from the same DT node. At the same time, I need the mux framework to handle the current out-of-node thing with a phandle as well, so that several mux consumers can share a common mux controller. My understanding of these matters are apparently not deep enough... I think you would like a DT that looks more like the first DT snippet but still enjoy the flexibility of the mux framework and w/o implementing a (another) full muxing sub-sub-system like the i2c sub-system has done. Correct? Cheers, peda -- 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