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Date:   Fri, 26 Feb 2021 08:32:59 +0900
From:   William Breathitt Gray <vilhelm.gray@gmail.com>
To:     Jonathan Cameron <jic23@kernel.org>
Cc:     kernel@pengutronix.de, linux-stm32@st-md-mailman.stormreply.com,
        a.fatoum@pengutronix.de, kamel.bouhara@bootlin.com,
        gwendal@chromium.org, alexandre.belloni@bootlin.com,
        david@lechnology.com, linux-iio@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        syednwaris@gmail.com, patrick.havelange@essensium.com,
        fabrice.gasnier@st.com, mcoquelin.stm32@gmail.com,
        alexandre.torgue@st.com, o.rempel@pengutronix.de,
        Dan Carpenter <dan.carpenter@oracle.com>
Subject: Re: [PATCH v8 19/22] counter: Implement extension*_name sysfs
 attributes
Message-ID: <YDgzq6t5YRm6cFvO@shinobu>
References: <cover.1613131238.git.vilhelm.gray@gmail.com>
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 <20210214180913.05bd3498@archlinux>
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On Sun, Feb 21, 2021 at 02:05:07PM +0000, Jonathan Cameron wrote:
> On Fri, 19 Feb 2021 17:51:37 +0900
> William Breathitt Gray <vilhelm.gray@gmail.com> wrote:
>=20
> > On Sun, Feb 14, 2021 at 06:09:13PM +0000, Jonathan Cameron wrote:
> > > On Fri, 12 Feb 2021 21:13:43 +0900
> > > William Breathitt Gray <vilhelm.gray@gmail.com> wrote:
> > >  =20
> > > > The Generic Counter chrdev interface expects users to supply extens=
ion
> > > > IDs in order to select extensions for requests. In order for users =
to
> > > > know what extension ID belongs to which extension this information =
must
> > > > be exposed. The extension*_name attribute provides a way for users =
to
> > > > discover what extension ID belongs to which extension by reading the
> > > > respective extension name for an extension ID.
> > > >=20
> > > > Cc: David Lechner <david@lechnology.com>
> > > > Cc: Gwendal Grignou <gwendal@chromium.org>
> > > > Cc: Dan Carpenter <dan.carpenter@oracle.com>
> > > > Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
> > > > ---
> > > >  Documentation/ABI/testing/sysfs-bus-counter |  9 ++++
> > > >  drivers/counter/counter-sysfs.c             | 51 +++++++++++++++++=
----
> > > >  2 files changed, 50 insertions(+), 10 deletions(-)
> > > >=20
> > > > diff --git a/Documentation/ABI/testing/sysfs-bus-counter b/Document=
ation/ABI/testing/sysfs-bus-counter
> > > > index 6353f0a2f8f8..847e96f19d19 100644
> > > > --- a/Documentation/ABI/testing/sysfs-bus-counter
> > > > +++ b/Documentation/ABI/testing/sysfs-bus-counter
> > > > @@ -100,6 +100,15 @@ Description:
> > > >  		Read-only attribute that indicates whether excessive noise is
> > > >  		present at the channel Y counter inputs.
> > > > =20
> > > > +What:		/sys/bus/counter/devices/counterX/countY/extensionZ_name
> > > > +What:		/sys/bus/counter/devices/counterX/extensionZ_name
> > > > +What:		/sys/bus/counter/devices/counterX/signalY/extensionZ_name
> > > > +KernelVersion:	5.13
> > > > +Contact:	linux-iio@vger.kernel.org
> > > > +Description:
> > > > +		Read-only attribute that indicates the component name of
> > > > +		Extension Z. =20
> > >=20
> > > Good to say what form this takes. =20
> >=20
> > Do you mean a description like this: "Read-only string attribute that
> > indicates the component name of Extension Z"?
>=20
> My expectation would be that the possible strings are tightly constrained
> (perhaps via review). So I'd like to see what they are and a brief descri=
ption
> of what each one means.
>=20
> Jonathan

Okay I see what you mean now. These names will match the sysfs attribute
filenames. So for example, if Extension 9 of Count 2 of Counter device
is /sys/bus/counter/devices/counter4/count2/ceiling, then the attribute
/sys/bus/counter/devices/counter4/count2/extension9_name will hold a
value of "ceiling".

The idea is that the user walks down through each extension*_name to
find sysfs attribute name for the Extension that they want. When they
find the desired Extension name in say sysfs attribute extension9_name,
then they know 9 is the ID number for that Extension.

There is an alternative design I was considering: instead of
extension*_name attributes, we could have each Extension sysfs attribute
have a matching *_extension_id attribute which provides the respective
Extension ID. So for example, using the same Extension as before:
/sys/bus/counter/devices/counter4/count2/ceiling_extension_id will hold
a value of 9.

Do you think this alternative design would be more intuitive to users?

William Breathitt Gray

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