From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dirk Behme Subject: Re: [PATCH 2/2] Documentation: gpio: board: describe the con_id parameter Date: Sun, 30 Aug 2015 11:14:27 +0200 Message-ID: <55E2C973.5060804@gmail.com> References: <1437808318-4453-1-git-send-email-dirk.behme@gmail.com> <1437808318-4453-2-git-send-email-dirk.behme@gmail.com> <55D60E53.60607@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-wi0-f170.google.com ([209.85.212.170]:37397 "EHLO mail-wi0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753440AbbH3JOb (ORCPT ); Sun, 30 Aug 2015 05:14:31 -0400 Received: by wicfv10 with SMTP id fv10so45486617wic.0 for ; Sun, 30 Aug 2015 02:14:29 -0700 (PDT) In-Reply-To: Sender: linux-gpio-owner@vger.kernel.org List-Id: linux-gpio@vger.kernel.org To: Alexandre Courbot Cc: "linux-gpio@vger.kernel.org" , Alexandre Courbot , Linus Walleij On 21.08.2015 05:01, Alexandre Courbot wrote: > On Fri, Aug 21, 2015 at 2:28 AM, Dirk Behme wrote: >> On 25.07.2015 09:11, Dirk Behme wrote: >>> >>> The con_id parameter has to match the GPIO description and is >>> automatically >>> extended by the GPIO suffix if not NULL. I had to look into the code to >>> understand this and properly find the GPIO I've been looking for, so >>> document >>> this. >>> >>> Signed-off-by: Dirk Behme >>> --- >>> Documentation/gpio/board.txt | 36 >>> ++++++++++++++++++++++++++++++++++++ >>> Documentation/gpio/consumer.txt | 3 +++ >>> 2 files changed, 39 insertions(+) >>> >>> diff --git a/Documentation/gpio/board.txt b/Documentation/gpio/board.txt >>> index 7605773..eac78fc 100644 >>> --- a/Documentation/gpio/board.txt >>> +++ b/Documentation/gpio/board.txt >>> @@ -48,6 +48,42 @@ This property will make GPIOs 15, 16 and 17 available >>> to the driver under the >>> The led GPIOs will be active-high, while the power GPIO will be >>> active-low (i.e. >>> gpiod_is_active_low(power) will be true). >>> >>> +If in the consumer device's node the property doesn't have a - >>> prefix, >>> +the second parameter (con_id) of the gpiod_get*() functions has to be >>> NULL: >>> + >>> +E.g. if in the above device tree example the GPIO array is just called >>> 'gpios' >>> + >>> + foo_device { >>> + compatible = "acme,foo"; >>> + ... >>> + gpios = <&gpio 15 GPIO_ACTIVE_HIGH>, /* red */ >>> + <&gpio 16 GPIO_ACTIVE_HIGH>, /* green */ >>> + <&gpio 17 GPIO_ACTIVE_HIGH>; /* blue */ >>> + }; >>> + >>> +the gpiod_get*() calls will be: >>> + >>> + struct gpio_desc *red, *green, *blue, *power; >>> + >>> + red = gpiod_get_index(dev, NULL, 0, GPIOD_OUT_HIGH); >>> + green = gpiod_get_index(dev, NULL, 1, GPIOD_OUT_HIGH); >>> + blue = gpiod_get_index(dev, NULL, 2, GPIOD_OUT_HIGH); >>> + >>> +To summarize: >>> + >>> +The con_id string parameter has to be either NULL or the >>> -prefix >>> +of the GPIO suffixes ("gpios" or "gpio", automatically looked up by the >>> +gpiod functions internally): >>> + >>> +* If the GPIO description is just named with one of the GPIO suffixes >>> + ("gpios" or "gpio"), use NULL. >>> +* If the GPIO description is prefixed with anything, e.g. "led-gpios", >>> use the >>> + prefix without the "-" as con_id parameter (in this example "led"). >>> + >>> +In case con_id is not NULL, the GPIO subsystem prefixes the GPIO suffix >>> +("gpios" or "gpio") with the string passed in con_id to get the resulting >>> string >>> +(snprintf(... "%s-%s", con_id, gpio_suffixes[]). >>> + >>> ACPI >>> ---- >>> ACPI also supports function names for GPIOs in a similar fashion to DT. >>> diff --git a/Documentation/gpio/consumer.txt >>> b/Documentation/gpio/consumer.txt >>> index 75542b9..47ce4fd 100644 >>> --- a/Documentation/gpio/consumer.txt >>> +++ b/Documentation/gpio/consumer.txt >>> @@ -39,6 +39,9 @@ device that displays digits), an additional index >>> argument can be specified: >>> const char *con_id, unsigned int >>> idx, >>> enum gpiod_flags flags) >>> >>> +For a more detailed description of the con_id parameter in the DeviceTree >>> case >>> +see Documentation/gpio/board.txt >>> + >>> The flags parameter is used to optionally specify a direction and >>> initial value >>> for the GPIO. Values can be: >> >> >> >> Any further comments on this? Or could this be applied? > > Using the "gpios" property is considered deprecated, so I am not sure > that is a good idea to mention this too extensively in the boards file > (people might be tempted to use that option while we clearly don't > want them to). > > A precise description of the lookup method is clearly missing though. > I don't know what the right place would be for it. consumer.txt? > board.txt in a more concise (and with a big "DEPRECATED") way? Ok, thanks! In a previous comment there was the proposal to put it into board.txt, as this applies only to the device tree case and board.txt has a device tree section. I'll drop the description of the deprecated part and send an update. Best regards Dirk