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

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Message-ID: <c3cc7f2a-ea0c-42a0-940c-95735d008989@gmail.com>
Date: Tue, 25 Feb 2025 12:07:37 +0200
From: Matti Vaittinen <mazziesaccount@...il.com>
To: 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>,
 Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 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>,
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 Olivier Moysan <olivier.moysan@...s.st.com>,
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 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 11:40, Heikki Krogerus wrote:
> Hi,
> 
>> +/**
>> + * 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)
>> +{
>> +	struct fwnode_handle *child;
>> +	unsigned int count = 0;
>> +
>> +	device_for_each_child_node(dev, child)
>> +		if (fwnode_name_eq(child, "channel"))
> 
> s/"channel"/name/ ?

Thanks Heikki for spotting this brainfart! :)

> 
>> +			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.

I have no strong opinion on this. It starts with just 1 user (IIO ADC 
channel stuff), but I've a feeling there are other areas which do 
look-up nodes by name. I suppose "channels" are looked-up in other areas 
of IIO as well. Lookups are probably done outside the IIO as well. I 
haven't audited this, but I wouldn't be surprized if at least LEDs (and 
perhaps clks/regulators?) could find this useful too.

> It just feels to special case to me. But let's see what the others
> think.

Yeah :) And thanks for spotting the "channel" -thing :)

Yours,
	-- Matti