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Date: Sun, 24 Sep 2017 14:56:04 -0500
From: Rob Herring <robh@...nel.org>
To: Linus Walleij <linus.walleij@...aro.org>
Cc: MyungJoo Ham <myungjoo.ham@...sung.com>,
Chanwoo Choi <cw00.choi@...sung.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
John Stultz <john.stultz@...aro.org>,
Mike Lockwood <lockwood@...gle.com>,
Guenter Roeck <linux@...ck-us.net>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH 1/8] extcon: gpio: Add DT bindings
On Sun, Sep 24, 2017 at 9:56 AM, Linus Walleij <linus.walleij@...aro.org> wrote:
> Add some reasonable device tree bindings and also add the cable defines
> to the extcon include in <dt-bindings/extcon/connectors.h> since
> the GPIO extcon definately need to specify which cable/connector it is
> detecting.
>
> Adding the include file makes the (as it happens) Linux numbers into an
> ABI, but I do not see any better method. It is possible to define strings
> for all cable types but it seems like overkill, just reusing Linux'
> enumerators seems like a good idea.
>
> The binding supports any number of GPIOs and connectors, but the driver
> currently only supports one connector on one GPIO line.
My view of extcon binding is it is fundamentally broken. I've
expressed this multiple times before.
TL;DR: Anything extending the existing extcon binding will be NAKed.
>
> Cc: devicetree@...r.kernel.org
> Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
> ---
> .../devicetree/bindings/extcon/extcon-gpio.txt | 24 ++++++++++++++
> include/dt-bindings/extcon/connectors.h | 38 ++++++++++++++++++++++
> 2 files changed, 62 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/extcon/extcon-gpio.txt
> create mode 100644 include/dt-bindings/extcon/connectors.h
>
> diff --git a/Documentation/devicetree/bindings/extcon/extcon-gpio.txt b/Documentation/devicetree/bindings/extcon/extcon-gpio.txt
> new file mode 100644
> index 000000000000..2f5e21b94a64
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/extcon/extcon-gpio.txt
> @@ -0,0 +1,24 @@
> +External Connector Using GPIO
What kind of connector? All connectors external to something... And
GPIO is not a kind of connector on its own, but an implementation.
> +
> +Required properties:
> +- compatible: should be "extcon-gpio"
> +- extcon-gpios: the GPIO lines used for the external connectors
This doesn't tell me what the GPIOs functions are and should. For
example we have hpd-gpios for HDMI hotplug detect in HDMI connector
binding.
> + See gpio/gpio.txt
> +- extcon-connector-types: set to an unsigned integer value arrat representing the types
> + of this connector, matched to the corresponding GPIO lines in the previous array.
This should be determined by the compatible string.
> + Those are defined with unique IDs in <dt-bindings/extcon/connectors.h>
> +- input-debounce: The number of microseconds to wait for the
> + connector state to stabilize. This property is reused from pin control
> + See pinctrl/pinctrl-bindings.txt
> +
> +Example:
> +
> +#include <dt-bindings/gpio/gpio.h>
> +#include <dt-bindings/extcon/connectors.h>
> +
> +extcon {
> + compatible = "extcon-gpio";
> + extcon-gpios = <&gpio0 42 GPIO_ACTIVE_LOW>;
> + extcon-connector-types = <EXTCON_USB>;
> + input-debounce = <20000>; /* 20 ms */
> +};
> diff --git a/include/dt-bindings/extcon/connectors.h b/include/dt-bindings/extcon/connectors.h
> new file mode 100644
> index 000000000000..61bed24eaadc
> --- /dev/null
> +++ b/include/dt-bindings/extcon/connectors.h
> @@ -0,0 +1,38 @@
> +#ifndef _DT_BINDINGS_EXTCON_CONNECTORS_H
> +#define _DT_BINDINGS_EXTCON_CONNECTORS_H
> +
> +/* USB external connector */
> +#define EXTCON_USB 1
> +#define EXTCON_USB_HOST 2
> +#define EXTCON_CHG_USB_SDP 5 /* Standard Downstream Port */
> +#define EXTCON_CHG_USB_DCP 6 /* Dedicated Charging Port */
> +#define EXTCON_CHG_USB_CDP 7 /* Charging Downstream Port */
> +#define EXTCON_CHG_USB_ACA 8 /* Accessory Charger Adapter */
> +#define EXTCON_CHG_USB_FAST 9
> +#define EXTCON_CHG_USB_SLOW 10
> +#define EXTCON_CHG_WPT 11 /* Wireless Power Transfer */
> +#define EXTCON_CHG_USB_PD 12 /* USB Power Delivery */
These don't all look to be mutually exclusive.
For USB PD, isn't that discoverable?
> +/* Jack external connector */
> +#define EXTCON_JACK_MICROPHONE 20
> +#define EXTCON_JACK_HEADPHONE 21
> +#define EXTCON_JACK_LINE_IN 22
> +#define EXTCON_JACK_LINE_OUT 23
> +#define EXTCON_JACK_VIDEO_IN 24
> +#define EXTCON_JACK_VIDEO_OUT 25
> +#define EXTCON_JACK_SPDIF_IN 26 /* Sony Philips Digital InterFace */
> +#define EXTCON_JACK_SPDIF_OUT 27
> +/* Display external connector */
> +#define EXTCON_DISP_HDMI 40 /* High-Definition Multimedia Interface */
> +#define EXTCON_DISP_MHL 41 /* Mobile High-Definition Link */
> +#define EXTCON_DISP_DVI 42 /* Digital Visual Interface */
> +#define EXTCON_DISP_VGA 43 /* Video Graphics Array */
> +#define EXTCON_DISP_DP 44 /* Display Port */
> +#define EXTCON_DISP_HMD 45 /* Head-Mounted Display */
We already have connector bindings for most of these. Use those as a
model for whatever you want to do.
> +/* Miscellaneous external connector */
> +#define EXTCON_DOCK 60
> +#define EXTCON_JIG 61
> +#define EXTCON_MECHANICAL 62
> +
> +#define EXTCON_NUM 63
> +
> +#endif /* _DT_BINDINGS_EXTCON_CONNECTORS_H */
> --
> 2.13.5
>
> --
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