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Received: from SN4PR0801MB3774.namprd08.prod.outlook.com (2603:10b6:803:43::21) by PH7PR08MB8229.namprd08.prod.outlook.com (2603:10b6:510:12c::10) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.7025.25; Sun, 26 Nov 2023 04:33:59 +0000 Received: from SN4PR0801MB3774.namprd08.prod.outlook.com ([fe80::36f2:78d1:ad7d:66da]) by SN4PR0801MB3774.namprd08.prod.outlook.com ([fe80::36f2:78d1:ad7d:66da%4]) with mapi id 15.20.7025.022; Sun, 26 Nov 2023 04:33:59 +0000 Date: Sat, 25 Nov 2023 22:33:53 -0600 From: Jeff LaBundy To: David Lechner Cc: Sicelo , linux-iio@vger.kernel.org, maemo-leste@lists.dyne.org, Ivaylo Dimitrov , linux-input@vger.kernel.org Subject: Re: supporting binary (near-far) proximity sensors over gpio Message-ID: References: Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-ClientProxiedBy: SA1P222CA0163.NAMP222.PROD.OUTLOOK.COM (2603:10b6:806:3c3::22) To SN4PR0801MB3774.namprd08.prod.outlook.com (2603:10b6:803:43::21) Precedence: bulk X-Mailing-List: linux-input@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SN4PR0801MB3774:EE_|PH7PR08MB8229:EE_ X-MS-Office365-Filtering-Correlation-Id: 8fb7b1e9-0ab5-4ada-7c0f-08dbee38e887 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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Thresholds are set at > > hardware level. One such sensor is OSRAM SFH 7741 [1], which is used on > > the Nokia N900. > > > > It is currently exported over evdev, emitting the SW_FRONT_PROXIMITY key > > code [2]. > > > > So the question is: should a new, general purpose iio-gpio driver be > > written, that would switch such a proximity sensor to the iio framework? > > Or evdev is really the best place to support it? > > > > There are a couple of people who are willing to write such an iio > > driver, if iio is the way to go. > > > > Regards, > > Sicelo > > > > [1] https://media.digikey.com/pdf/Data%20Sheets/Osram%20PDFs/SFH_7741.pdf > > [2] https://elixir.bootlin.com/linux/v6.6.1/source/arch/arm/boot/dts/ti/omap/omap3-n900.dts#L111 > > > Since this is really a proximity switch (it is either on or off) > rather than measuring a proximity value over a continuous range, it > doesn't seem like a good fit for the iio subsystem. If the sensor is > on a phone, then it is likely to detect human presence so the input > subsystem does seem like the right one for that application. > > More at https://www.kernel.org/doc/html/latest/driver-api/iio/intro.html > I tend to agree; if there are only two discrete states as is the case for a GPIO, then this is technically a switch and not a sensor. Therefore, input seems like a better fit; that is just my $.02. FWIW, a similar discussion came up a few years ago in [1] and again the key differentiator was whether the output is discrete or continuous. Kind regards, Jeff LaBundy [1] https://lore.kernel.org/linux-iio/9f9b0ff6-3bf1-63c4-eb36-901cecd7c4d9@redhat.com/