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 X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 310AAC43381 for ; Sun, 3 Mar 2019 17:12:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D8AFE20830 for ; Sun, 3 Mar 2019 17:12:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1551633122; bh=f/S18H9ehKsgU6fh76nFR+CAvXDVm3KwaXwt/OcdCMY=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=m4NUCYOv+7o9WyOBsWpiykLhq34yfKFvTinb4y4Q9GIn3OeLuwbEnMCpI9+w+UI4g yKVlflPh5PE2w38HuHbkbR55xdVIYHLieAIQRZ86Hhv+SMxRRkjvUhDwVVsHXWjV+d ZIUltjHveGfoqtIye5uKNjQY1oWyimLvUUTeY3CY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726442AbfCCRMB (ORCPT ); Sun, 3 Mar 2019 12:12:01 -0500 Received: from mail.kernel.org ([198.145.29.99]:55898 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726476AbfCCRMA (ORCPT ); Sun, 3 Mar 2019 12:12:00 -0500 Received: from archlinux (cpc91196-cmbg18-2-0-cust659.5-4.cable.virginm.net [81.96.234.148]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 35BB820818; Sun, 3 Mar 2019 17:11:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1551633119; bh=f/S18H9ehKsgU6fh76nFR+CAvXDVm3KwaXwt/OcdCMY=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Zb9HFU+cCQcwRfa3lmOe5h9F336ov71klX/pm4TIdB3zLYg6AcYi8P4QbM26feqjN Ga7OOd5o/z2BKEfq7r5SD+hQQeN83P38qUWR/waYz1mNr3W4LqOxOY4bSsBjyI4BNK rr+cJ7rqwHd5GNtcuDJFiHt9KhAArmG81G19m+mE= Date: Sun, 3 Mar 2019 17:11:54 +0000 From: Jonathan Cameron To: Michael Nazzareno Trimarchi Cc: Lars-Peter Clausen , Hartmut Knaack , Peter Meerwald-Stadler , linux-iio@vger.kernel.org Subject: Re: [PATCH] iio: potentiometer: add driver for Maxim Integrated DS1807 Message-ID: <20190303171154.1838e05f@archlinux> In-Reply-To: References: <1525613447-32734-1-git-send-email-michael@amarulasolutions.com> <20180506183745.325e67b8@archlinux> <96251f75-6a0b-9668-b103-8d2453bf8bba@metafoo.de> <20180507181714.34760596@archlinux> <20180512104533.7d74aa01@archlinux> <20180512120750.182a9de1@archlinux> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-iio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org On Sat, 23 Feb 2019 10:04:31 +0100 Michael Nazzareno Trimarchi wrote: > Hi Jonathan > > Very old thread. I have created Giotto Tune based on this design and > now try to attach to ds1807. I have done some hack on the current > interface to have it working in alsa. I have some trouble with the API > > fragment@3 { > target = <&sound>; > __overlay__ { > compatible = "bcm2708,bcm2708-audio-giotto"; > i2s-controller = <&i2s>; > io-channels = <&volume 0>; This is a list, not just one. > #io-channel-cells = <1>; > nreset = <&gpio 5 1>; > status = "okay"; > }; > }; > > fragment@4 { > target = <&spidev0>; > __overlay__ { > status = "disabled"; > }; > }; > > fragment@5 { > target = <&i2c1>; > __overlay__ { > #address-cells = <1>; > #size-cells = <0>; > status = "okay"; > > volume: ds1807@1 { > compatible = "maxim,ds1807"; > reg = <0x28>; > status = "okay"; > #io-channel-cells = <1>; > }; > }; > }; > > This is the overlay and this is the change of the API > > -static int iio_channel_write(struct iio_channel *chan, int val, int val2, > +static int iio_channel_write(struct iio_channel *chan, int index, int > val, int val2, > enum iio_chan_info_enum info) > { > return chan->indio_dev->info->write_raw(chan->indio_dev, > - chan->channel, val, val2, info); > + &chan->channel[index], > val, val2, info); > } > > +int iio_write_channel_attribute(struct iio_channel *chan, int index, > int val, int val2, > + enum iio_chan_info_enum attribute) > +{ > + int ret; > + > + mutex_lock(&chan->indio_dev->info_exist_lock); > + if (chan->indio_dev->info == NULL) { > + ret = -ENODEV; > + goto err_unlock; > + } > + > + if (index < 0 || index > chan->indio_dev->num_channels) > + return -EINVAL; > + > + ret = iio_channel_write(chan, index, val, val2, attribute); > +err_unlock: > + mutex_unlock(&chan->indio_dev->info_exist_lock); > + > + return ret; > +} > +EXPORT_SYMBOL_GPL(iio_write_channel_attribute); > > I order to trigger both controls > > + ret = iio_write_channel_attribute(&data->iio_ch[0], 0, > + val, 0, > + IIO_CHAN_INFO_HARDWAREGAIN); > + if (ret < 0) > + return ret; > + > + ret = iio_write_channel_attribute(&data->iio_ch[0], 1, > + val, 0, > + IIO_CHAN_INFO_HARDWAREGAIN); > + if (ret < 0) > + return ret; > + > > The problem is that we can have one iio_dev and multiple raw value for > each one. Absolutely we can, but you need to register multiple channels and get them all, not just one and then try and build off that. > Is this the correct way? No. You need to have multiple channels listed, not just the one. There are examples in Documentation/bindings/iio/iio-bindings.txt I may be misunderstanding what you are trying to do. Jonathan > > Michael > > On Sat, May 12, 2018 at 2:10 PM Michael Nazzareno Trimarchi > wrote: > > > > Hi > > > > On Sat, May 12, 2018 at 1:07 PM, Jonathan Cameron wrote: > > > On Sat, 12 May 2018 11:50:23 +0200 > > > Michael Nazzareno Trimarchi wrote: > > > > > >> Hi > > >> > > >> On Sat, May 12, 2018 at 11:45 AM, Jonathan Cameron wrote: > > >> > On Wed, 9 May 2018 11:19:51 +0200 > > >> > Michael Nazzareno Trimarchi wrote: > > >> > > > >> >> Hi Jonathan > > >> >> > > >> >> > > >> >> On Wed, May 9, 2018 at 11:01 AM, Michael Nazzareno Trimarchi > > >> >> wrote: > > >> >> > Hi > > >> >> > > > >> >> > On Mon, May 7, 2018 at 7:17 PM, Jonathan Cameron wrote: > > >> >> >> On Mon, 7 May 2018 18:55:16 +0200 > > >> >> >> Lars-Peter Clausen wrote: > > >> >> >> > > >> >> >>> On 05/07/2018 06:44 PM, Lars-Peter Clausen wrote: > > >> >> >>> > On 05/06/2018 07:37 PM, Jonathan Cameron wrote: > > >> >> >>> >> On Sun, 6 May 2018 15:30:47 +0200 > > >> >> >>> >> Michael Trimarchi wrote: > > >> >> >>> >> > > >> >> >>> >>> The following functions are supported: > > >> >> >>> >>> - write, read potentiometer value > > >> >> >>> >>> > > >> >> >>> >>> Value are exported in DBm because it's used as an audio > > >> >> >>> >>> attenuator > > >> >> >>> >> > > >> >> >>> >> This is interesting. The problem is that there is no way for > > >> >> >>> >> userspace to know that it is reporting in DBm rather than > > >> >> >>> >> reporting a linear gain or a straight forward resistance. > > >> >> >>> >> > > >> >> >>> >> This is rather closer in operation to the analog front end > > >> >> >>> >> driver I took the other day than to the other potentiometers > > >> >> >>> >> we have drivers for. > > >> >> >>> >> > > >> >> >>> >> Anyhow, how to solve this? Two options come to mind. > > >> >> >>> >> 1) Look up table mapping to linear gain as per current ABI > > >> >> >>> >> 2) Add a new channel type to represent the fact we are > > >> >> >>> >> looking at a logarithmic value, letting us handle it as DB. > > >> >> >>> > > > >> >> >>> > Yeah, I guess it is a bit difficult. I don't think this should be a separate > > >> >> >>> > type since we are still describing the same thing, just the scale is > > >> >> >>> > logarithmic rather than linear. Translation table doesn't work either since > > >> >> >>> > your values would get ridiculous small/large. We could add a db suffix to > > >> >> >>> > the type, but that's just terrible. I guess the best we can do is have a > > >> >> >>> > scale attribute that says 1dB. > > >> >> >>> > > >> >> >>> The other problem of course is that dB is a relative unit. The ratio of one > > >> >> >>> value to another. Whereas our normal scale refers to an absolute value. > > >> >> >> I'm really not keen on this. We have done the separate types > > >> >> >> for humidity already, where we had relative (which is a ratio) and absolute > > >> >> >> (which isn't). It's not pretty though. > > >> >> >> > > >> >> >> Potentially we could define a new attribute that says this one is > > >> >> >> is db or linear but that's ugly too. > > >> >> >> > > >> >> >> As you asked, are we looking at a part that gets used for anything other > > >> >> >> than audio or not? If just audio, alsa driver does indeed make more sense. > > >> >> >> > > >> >> > > > >> >> > This can be used in audio but even in other field. It's just a potentiometer. > > >> >> > Can I know what is wrong to use the same approch of audio ampliefier that we > > >> >> > have already in the iio tree? > > >> >> > > > >> >> > > >> >> cat /sys/bus/iio/devices/iio:device1/out_altvoltage0_hardwaregain > > >> >> -10.000000 dB > > >> >> echo -10 > /sys/bus/iio/devices/iio:device1/out_altvoltage0_hardwaregain > > >> > > > >> > Wow, somehow that entire thing had slipped my mind. I guess we went > > >> > through the whole question of how to support dB scales years ago > > >> > and it has just been very little used. > > >> > > > >> > Hmm. Sorry for my absent mindedness! Anyhow, there are a few additional > > >> > comments that need cleaning up. > > >> > > > >> > It is going to be a little odd as the only potentiometer (I think) that > > >> > is acting as a scale free attenuator, rather that being controlled on the basis > > >> > of resistance, but for the part that seems to make sense so fair enough. > > >> > > > >> > I'm slightly curious to know what you have this wired up to though? > > >> > > >> I'm design GIOTTO ;) an audio module that use those to control the > > >> volume. It's a dsd > > >> native sound card that demultiplex i2s to L and R dsd on a pcm1795a. > > >> Everything already > > >> run under linux. The idea is to create an audio card and connect iio > > >> device to the volume > > >> to change dsd volume > > >> > > >> > Are the inputs and outputs invisible to the kernel or is this feeding > > >> > into another device? > > >> > > >> I think a reply above. Anyway we don't want to have driver duplication > > >> and I think should be land > > >> there > > >> > > >> > > > >> > If we are feeding another device then the work recently done on a > > >> > generic AFE driver may be useful. At somepoint we'll need a version > > >> > > >> Can you point to it? I need to read about ;) > > > > > > https://patchwork.kernel.org/patch/10358131/ > > > > > > Should be in linux-next by now ready for the next merge window. > > > As it turns out, probably not relevant in your case you will > > > probably want to have the sound card as a consumer so that > > > the volume control maps nicely via usual interface etc. > > > > > > Perhaps cc the relevant sound lists and maintainers on next version. > > > I don't want to tread on anyone's toes if they are of the view that > > > it shouldn't be done this way (should be fine from previous conversations > > > with a few of them!) > > > > Yes it's a good idea. I will try but I need to move my development > > board on latest > > kernel. > > > > Michael > > > > > > > > Jonathan > > > > > >> > > >> Michael > > >> > > >> > of that which deals with standalone amplifiers and attenuators anyway, > > >> > but I don't know if it is useful to you. > > >> > > > >> > Jonathan > > >> > > > >> > Jonathan > > >> > > > >> > > > >> >> > > >> >> uname -a > > >> >> Linux linaro-alip 4.4.93 #7 SMP Sun May 6 13:23:08 CEST 2018 armv7l GNU/Linux > > >> >> > > >> >> Michael > > >> >> > > >> >> > Michael > > >> >> > > > >> >> >> Jonathan > > >> >> > > > >> >> > > > >> >> > > > >> >> > -- > > >> >> > | Michael Nazzareno Trimarchi Amarula Solutions BV | > > >> >> > | COO - Founder Cruquiuskade 47 | > > >> >> > | +31(0)851119172 Amsterdam 1018 AM NL | > > >> >> > | [`as] http://www.amarulasolutions.com | > > >> >> > > >> >> > > >> >> > > >> > > > >> > > >> > > >> > > > > > > > > > > > -- > > | Michael Nazzareno Trimarchi Amarula Solutions BV | > > | COO - Founder Cruquiuskade 47 | > > | +31(0)851119172 Amsterdam 1018 AM NL | > > | [`as] http://www.amarulasolutions.com | > > >