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

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Message-ID: <ad39b453-7e5b-49bd-a4fd-6a4988636130@gmail.com>
Date: Tue, 25 Feb 2025 12:29:31 +0200
From: Matti Vaittinen <mazziesaccount@...il.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
 Jonathan Cameron <jic23@...nel.org>, Lars-Peter Clausen <lars@...afoo.de>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Daniel Scally <djrscally@...il.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>,
 Javier Carrasco <javier.carrasco.cruz@...il.com>,
 Guillaume Stols <gstols@...libre.com>,
 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 25/02/2025 12:21, Andy Shevchenko wrote:
> On Tue, Feb 25, 2025 at 11:40:16AM +0200, Heikki Krogerus wrote:
>>> +/**
>>> + * 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
> 
> This has an inconsistent kernel doc structure in comparison to the rest in this
> file.
> 
>>> + * 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)
>>> +{
>>> +	struct fwnode_handle *child;
>>> +	unsigned int count = 0;
>>> +
>>> +	device_for_each_child_node(dev, child)
>>> +		if (fwnode_name_eq(child, "channel"))
>>
>> s/"channel"/name/ ?
>>
>>> +			count++;
>>> +
>>> +	return count;
>>> +}
>>> +EXPORT_SYMBOL_GPL(device_get_child_node_count_named);
>>
>> I did not check how many users are you proposing for this, but if
>> there's only one, then IMO this should not be a global function yet.
>> It just feels to special case to me. But let's see what the others
>> think.
> 
> The problem is that if somebody hides it, we might potentially see
> a duplication in the future. So I _slightly_ prefer to publish and
> then drop that after a few cycles if no users appear.

After taking a very quick grep I spotted one other existing place where 
we might be able to do direct conversion to use this function.

drivers/net/ethernet/freescale/gianfar.c

That'd be 2 users.

While I looked at it, it seems that a 
'device_for_each_named_child_node()' -construct would have a few users.

Yours,
	-- Matti