From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E651AC433F5 for ; Mon, 14 Feb 2022 08:53:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240571AbiBNIxU (ORCPT ); Mon, 14 Feb 2022 03:53:20 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:50548 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231279AbiBNIxT (ORCPT ); Mon, 14 Feb 2022 03:53:19 -0500 Received: from relay1-d.mail.gandi.net (relay1-d.mail.gandi.net [IPv6:2001:4b98:dc4:8::221]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3EF095F8F9 for ; Mon, 14 Feb 2022 00:53:11 -0800 (PST) Received: (Authenticated sender: miquel.raynal@bootlin.com) by mail.gandi.net (Postfix) with ESMTPSA id 41C8224000B; Mon, 14 Feb 2022 08:53:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1644828789; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=zmMKuegqj8C5AxdwdBJAjd25tIgLBBLsw4Hr7MEGK+Q=; b=ZrcEA/39QXLwzPiA0wGJtGym7dCOhJmc4dWq6Wi5G6SgWQBUN/iQRWf4YbAs+vuSzys+CK 267GSuTr/k3DF3hVQFFjGEdjxUx8nMF7oVTwbkQl6CgB1+4bW+zeZFO05KKTHiYmCm5NMs ubHFDXaKaHgu6pz7E5F6djpotNebYx4A8dSRGIfo5B5layQLIsckAo3HqOuEXy/P5q2Fao 30kWNSZZ6jGr6FozG3EsY3m0A1aDjk23iCbspGYfCqzuS4hOrIVXiUrsPdNTCViCHQlplm p5v2L4XMDUx1CMv/zDKej/FvNi7zxV08pAamJltVrTddL0XmoZAH5AKl5BH43Q== Date: Mon, 14 Feb 2022 09:53:08 +0100 From: Miquel Raynal To: Jonathan Cameron Cc: linux-iio@vger.kernel.org, Lars-Peter Clausen , Thomas Petazzoni , Alexandru Ardelean Subject: Re: [PATCH v3 13/13] iio: core: Clarify the modes Message-ID: <20220214095308.42e52f34@xps13> In-Reply-To: <20220213184224.1644ddbc@jic23-huawei> References: <20220207143840.707510-1-miquel.raynal@bootlin.com> <20220207143840.707510-14-miquel.raynal@bootlin.com> <20220213184224.1644ddbc@jic23-huawei> Organization: Bootlin X-Mailer: Claws Mail 3.17.7 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org Hi Jonathan, jic23@kernel.org wrote on Sun, 13 Feb 2022 18:42:24 +0000: > On Mon, 7 Feb 2022 15:38:40 +0100 > Miquel Raynal wrote: >=20 > > As part of a previous discussion with Jonathan Cameron [1], it appeared > > necessary to clarify the meaning of each mode so that new developers > > could understand better what they should use or not use and when. > >=20 > > The idea of renaming these modes as been let aside because naming is a > > big deal and requires a lot of thinking. So for now let's focus on > > correctly explaining what each mode implies. > >=20 > > [1] https://lore.kernel.org/linux-iio/20210930165510.2295e6c4@jic23-hua= wei/ > >=20 > > Suggested-by: Jonathan Cameron > > Signed-off-by: Miquel Raynal =20 > One trivial thing inline as a result of edits in v3. >=20 > Otherwise, I want to let this series sit a little longer and ideally get > some eyes on the st_sensors patches. Sure. >=20 > Jonathan >=20 > > --- > > include/linux/iio/iio.h | 49 ++++++++++++++++++++++++++++++++++++++++- > > 1 file changed, 48 insertions(+), 1 deletion(-) > >=20 > > diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h > > index 85cb924debd9..e383b0d96035 100644 > > --- a/include/linux/iio/iio.h > > +++ b/include/linux/iio/iio.h > > @@ -315,7 +315,54 @@ static inline bool iio_channel_has_available(const= struct iio_chan_spec *chan, > > s64 iio_get_time_ns(const struct iio_dev *indio_dev); > > unsigned int iio_get_time_res(const struct iio_dev *indio_dev); > > =20 > > -/* Device operating modes */ > > +/** > > + * Device operating modes > > + * @INDIO_DIRECT_MODE: There is an access to either: > > + * a) The last single value available for devices that do not provide > > + * on-demand reads. > > + * b) A new value after performing an on-demand read otherwise. =20 >=20 >=20 > > + * On most devices, this is a single-shot read. On some devices with d= ata > > + * streams without an 'on-demand' function, this might also be the 'la= st value' > > + * feature. =20 >=20 > This block duplicates what you now have as a/b above. I can drop it whilst > applying if nothing else comes up. We can get rid of it indeed. Let's see what ST people have in mind regarding the st_sensors patches. > > Above all, this mode internally means that we are not in any of the > > + * other modes, and sysfs reads should work. > > + * Device drivers should inform the core if they support this mode. > > + * @INDIO_BUFFER_TRIGGERED: Common mode when dealing with kfifo buffer= s. > > + * It indicates that an explicit trigger is required. This requests th= e core to > > + * attach a poll function when enabling the buffer, which is indicated= by the > > + * _TRIGGERED suffix. > > + * The core will ensure this mode is set when registering a triggered = buffer > > + * with iio_triggered_buffer_setup(). > > + * @INDIO_BUFFER_SOFTWARE: Another kfifo buffer mode, but not event tr= iggered. > > + * No poll function can be attached because there is no triggered infr= astructure > > + * we can use to cause capture. There is a kfifo that the driver will = fill, but > > + * not "only one scan at a time". Typically, hardware will have a buff= er that > > + * can hold multiple scans. Software may read one or more scans at a s= ingle time > > + * and push the available data to a Kfifo. This means the core will no= t attach > > + * any poll function when enabling the buffer. > > + * The core will ensure this mode is set when registering a simple kfi= fo buffer > > + * with devm_iio_kfifo_buffer_setup(). > > + * @INDIO_BUFFER_HARDWARE: For specific hardware, if unsure do not use= this mode. > > + * Same as above but this time the buffer is not a kfifo where we have= direct > > + * access to the data. Instead, the consumer driver must access the da= ta through > > + * non software visible channels (or DMA when there is no demux possib= le in > > + * software) > > + * The core will ensure this mode is set when registering a dmaengine = buffer > > + * with devm_iio_dmaengine_buffer_setup(). > > + * @INDIO_EVENT_TRIGGERED: Very unusual mode. > > + * Triggers usually refer to an external event which will start data c= apture. > > + * Here it is kind of the opposite as, a particular state of the data = might > > + * produce an event which can be considered as an event. We don't nece= ssarily > > + * have access to the data itself, but to the event produced. For exam= ple, this > > + * can be a threshold detector. The internal path of this mode is very= close to > > + * the INDIO_BUFFER_TRIGGERED mode. > > + * The core will ensure this mode is set when registering a triggered = event. > > + * @INDIO_HARDWARE_TRIGGERED: Very unusual mode. > > + * Here, triggers can result in data capture and can be routed to mult= iple > > + * hardware components, which make them close to regular triggers in t= he way > > + * they must be managed by the core, but without the entire interrupts= /poll > > + * functions burden. Interrupts are irrelevant as the data flow is har= dware > > + * mediated and distributed. > > + */ > > #define INDIO_DIRECT_MODE 0x01 > > #define INDIO_BUFFER_TRIGGERED 0x02 > > #define INDIO_BUFFER_SOFTWARE 0x04 =20 >=20 Thanks, Miqu=C3=A8l