linux-kernel - Re: [PATCH v4 02/10] property: Add device_get_child_node_count

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Message-ID: <CAL_Jsq+av-fptMQqBeVieKwA9c7+uUCaqZMLGu-RVJzWZ_7+Vg@mail.gmail.com>
Date: Fri, 28 Feb 2025 11:07:24 -0600
From: Rob Herring <robh@...nel.org>
To: Matti Vaittinen <mazziesaccount@...il.com>
Cc: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>, Jonathan Cameron <jic23@...nel.org>, 
	Lars-Peter Clausen <lars@...afoo.de>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Daniel Scally <djrscally@...il.com>, 
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>, 
	Sakari Ailus <sakari.ailus@...ux.intel.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	Danilo Krummrich <dakr@...nel.org>, Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>, 
	Chen-Yu Tsai <wens@...e.org>, Jernej Skrabec <jernej.skrabec@...il.com>, 
	Samuel Holland <samuel@...lland.org>, Hugo Villeneuve <hvilleneuve@...onoff.com>, 
	Nuno Sa <nuno.sa@...log.com>, David Lechner <dlechner@...libre.com>, 
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	Olivier Moysan <olivier.moysan@...s.st.com>, Dumitru Ceclan <mitrutzceclan@...il.com>, 
	Trevor Gamblin <tgamblin@...libre.com>, Matteo Martelli <matteomartelli3@...il.com>, 
	Alisa-Dariana Roman <alisadariana@...il.com>, 
	Ramona Alexandra Nechita <ramona.nechita@...log.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, linux-iio@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-acpi@...r.kernel.org, linux-renesas-soc@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev
Subject: Re: [PATCH v4 02/10] property: Add device_get_child_node_count_named()

On Mon, Feb 24, 2025 at 12:33 PM Matti Vaittinen
<mazziesaccount@...il.com> wrote:
>
> There are some use-cases where child nodes with a specific name need to
> be parsed. In a few cases the data from the found nodes is added to an
> array which is allocated based on the number of found nodes. One example
> of such use is the IIO subsystem's ADC channel nodes, where the relevant
> nodes are named as channel[@N].
>
> Add a helper for counting device's sub-nodes with certain name instead
> of open-coding this in every user.
>
> Suggested-by: Jonathan Cameron <jic23@...nel.org>
> Signed-off-by: Matti Vaittinen <mazziesaccount@...il.com>
> ---
> Revision history:
> v3 => v4:
>  - New patch as suggested by Jonathan, see discussion in:
> https://lore.kernel.org/lkml/20250223161338.5c896280@jic23-huawei/
> ---
>  drivers/base/property.c  | 28 ++++++++++++++++++++++++++++
>  include/linux/property.h |  2 ++
>  2 files changed, 30 insertions(+)
>
> diff --git a/drivers/base/property.c b/drivers/base/property.c
> index c1392743df9c..3f85818183cd 100644
> --- a/drivers/base/property.c
> +++ b/drivers/base/property.c
> @@ -945,6 +945,34 @@ unsigned int device_get_child_node_count(const struct device *dev)
>  }
>  EXPORT_SYMBOL_GPL(device_get_child_node_count);
>
> +/**
> + * device_get_child_node_count_named - number of child nodes with given name
> + *
> + * Scan device's child nodes and find all the nodes with a specific name and
> + * return the number of found nodes. Potential '@...ber' -ending for scanned
> + * names is ignored. Eg,
> + * device_get_child_node_count(dev, "channel");
> + * would match all the nodes:
> + * channel { }, channel@0 {}, channel@...bba {}...
> + *
> + * @dev: Device to count the child nodes for
> + *
> + * Return: the number of child nodes with a matching name for a given device.
> + */
> +unsigned int device_get_child_node_count_named(const struct device *dev,
> +                                              const char *name)

I think this should be implemented as
fwnode_get_child_node_count_named() with the device variant being just
a wrapper.

Rob