Re: [PATCH v3 12/15] iio: adc: qcom-spmi-adc5: convert to device properties

From: Marijn Suijten <marijn.suijten@somainline.org>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: "Jonathan Cameron" <jic23@kernel.org>,
	"Nuno Sá" <nuno.sa@analog.com>,
	openbmc@lists.ozlabs.org, linux-imx@nxp.com,
	linux-stm32@st-md-mailman.stormreply.com,
	linux-iio@vger.kernel.org, linux-mips@vger.kernel.org,
	linux-renesas-soc@vger.kernel.org,
	linux-mediatek@lists.infradead.org,
	chrome-platform@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org,
	"Lad Prabhakar" <prabhakar.mahadev-lad.rj@bp.renesas.com>,
	linux-arm-msm@vger.kernel.org,
	"Gwendal Grignou" <gwendal@chromium.org>,
	"Fabio Estevam" <festevam@gmail.com>,
	"Tali Perry" <tali.perry1@gmail.com>,
	"Nicolas Ferre" <nicolas.ferre@microchip.com>,
	"Pengutronix Kernel Team" <kernel@pengutronix.de>,
	"Fabrice Gasnier" <fabrice.gasnier@foss.st.com>,
	"Daniel Lezcano" <daniel.lezcano@linaro.org>,
	"Miquel Raynal" <miquel.raynal@bootlin.com>,
	"Eugen Hristev" <eugen.hristev@microchip.com>,
	"Matthias Brugger" <matthias.bgg@gmail.com>,
	"Lars-Peter Clausen" <lars@metafoo.de>,
	"Paul Cercueil" <paul@crapouillou.net>,
	"Claudiu Beznea" <claudiu.beznea@microchip.com>,
	"Michael Hennerich" <Michael.Hennerich@analog.com>,
	"Haibo Chen" <haibo.chen@nxp.com>
Subject: Re: [PATCH v3 12/15] iio: adc: qcom-spmi-adc5: convert to device properties
Date: Tue, 17 Jan 2023 23:42:51 +0100	[thread overview]
Message-ID: <20230117224251.wzxexdlfe5ydzjw5@SoMainline.org> (raw)
In-Reply-To: <CAHp75VdyCA7mQdm--kg=hUbmQqX4-jfFMHgLxref5mNSM1vnMA@mail.gmail.com>

On 2023-01-17 11:40:42, Andy Shevchenko wrote:
<snip>
> > > > This CC just surfaced in my inbox while searching for our current
> > > > discussion around missing labels in qcom-spmi-vadc - and on the side a
> > > > userspace @xx label name ABI break (in qcom-spmi-adc5) caused by this
> > > > patch's fwnode_get_name change - we could've caught it if I had not
> > > > accidentally marked it as read and/or forgot about it.  My apologies.
> > >
> > > Does the following addition to the top of the
> > > adc5_get_fw_channel_data() fix the issue?
> > >
> > > +       name = devm_kasprintf(adc->dev, GFP_KERNEL, "%pfwP", fwnode);
> > > +       if (!name)
> > > +               return -ENOMEM;
> >
> > Okay, it probably the same, so it might need additional code to
> >
> > + name[strchrnul(name, '@') - name] = '\0';
> 
> I have just sent a formal patch, please test on top of non-working kernel.

I would've preferred to fix this in the same way as qcom-spmi-vadc by
implementing read_label instead and basing it on the DT label or driver
string literals instead [1], but dropping extend_name (hence changing
sysfs filenames once again) would be considered an ABI break.

I've instead gone for a similar change that also ignores the node name
in favour of falling back to the driver string literal (if no "label"
property is available) while retaining extend_label [3] and the -
however ugly they are - sysfs filenames, but that'll likely get rejected
as strictly being an ABI break as well, not in the least because DT
needs to be patched up [3] for it to work out.

I'll at least test your patch when getting back to one of these devices.

- Marijn

[1]: https://lore.kernel.org/linux-arm-msm/20230116220909.196926-6-marijn.suijten@somainline.org/
[2]: https://lore.kernel.org/linux-arm-msm/20230116220909.196926-4-marijn.suijten@somainline.org/
[3]: https://lore.kernel.org/linux-arm-msm/20221209215308.1781047-1-marijn.suijten@somainline.org/