linux-kernel - Re: [PATCH v2 01/11] of: Add wrappers to match root node with OF device ID tables

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Message-ID: <CAMuHMdVAZpp7M+pp27+kHZwoet2Q8Rm-Y4ePu7=W_1oXhebLmQ@mail.gmail.com>
Date: Tue, 2 Dec 2025 15:07:03 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc: Rob Herring <robh@...nel.org>, Saravana Kannan <saravanak@...gle.com>, 
	"Rafael J. Wysocki" <rafael@...nel.org>, Viresh Kumar <viresh.kumar@...aro.org>, 
	Matthias Brugger <matthias.bgg@...il.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
	Yangtao Li <tiny.windzz@...il.com>, Chen-Yu Tsai <wens@...nel.org>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Samuel Holland <samuel@...lland.org>, 
	Lorenzo Pieralisi <lpieralisi@...nel.org>, Daniel Lezcano <daniel.lezcano@...aro.org>, 
	Bjorn Andersson <andersson@...nel.org>, Konrad Dybcio <konradybcio@...nel.org>, 
	Thomas Gleixner <tglx@...utronix.de>, Nicolas Ferre <nicolas.ferre@...rochip.com>, 
	Alexandre Belloni <alexandre.belloni@...tlin.com>, Claudiu Beznea <claudiu.beznea@...on.dev>, 
	Maximilian Luz <luzmaximilian@...il.com>, Hans de Goede <hansg@...nel.org>, 
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>, 
	Daniel Lezcano <daniel.lezcano@...nel.org>, Thierry Reding <thierry.reding@...il.com>, 
	Jonathan Hunter <jonathanh@...dia.com>, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org, 
	linux-sunxi@...ts.linux.dev, linux-arm-msm@...r.kernel.org, 
	platform-driver-x86@...r.kernel.org, linux-tegra@...r.kernel.org
Subject: Re: [PATCH v2 01/11] of: Add wrappers to match root node with OF
 device ID tables

Hi Krzysztof,

Thanks for your patch, which is now commit 4a93adcbd201aad5
("of: Add wrappers to match root node with OF device ID tables")
in dt-rh/for-next.

On Wed, 12 Nov 2025 at 11:30, Krzysztof Kozlowski
<krzysztof.kozlowski@...aro.org> wrote:
> Several drivers duplicate same code for getting reference to the root
> node, matching it against 'struct of_device_id' table and getting out
> the match data from the table entry.
>
> There is a of_machine_compatible_match() wrapper but it takes array of
> strings, which is not suitable for many drivers since they want the
> driver data associated with each compatible.
>
> Add two wrappers, similar to existing of_device_get_match_data():
> 1. of_machine_device_match() doing only matching against 'struct
>    of_device_id' and returning bool.
> 2. of_machine_get_match_data() doing the matching and returning
>    associated driver data for found compatible.

Shouldn't the first function be called of_match_machine(), and return
a const struct of_device_id *, cfr. of_match_device()?

>
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>

> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -434,6 +434,53 @@ bool of_machine_compatible_match(const char *const *compats)
>  }
>  EXPORT_SYMBOL(of_machine_compatible_match);
>
> +/**
> + * of_machine_device_match - Test root of device tree against a of_device_id array
> + * @matches:   NULL terminated array of of_device_id match structures to search in
> + *
> + * Returns true if the root node has any of the given compatible values in its
> + * compatible property.
> + */
> +bool of_machine_device_match(const struct of_device_id *matches)
> +{
> +       struct device_node *root;
> +       const struct of_device_id *match = NULL;
> +
> +       root = of_find_node_by_path("/");
> +       if (root) {
> +               match = of_match_node(matches, root);
> +               of_node_put(root);
> +       }
> +
> +       return match != NULL;
> +}
> +EXPORT_SYMBOL(of_machine_device_match);
> +
> +/**
> + * of_machine_get_match_data - Tell if root of device tree has a matching of_match structure
> + * @matches:   NULL terminated array of of_device_id match structures to search in
> + *
> + * Returns data associated with matched entry or NULL
> + */
> +const void *of_machine_get_match_data(const struct of_device_id *matches)
> +{
> +       const struct of_device_id *match;
> +       struct device_node *root;
> +
> +       root = of_find_node_by_path("/");
> +       if (!root)
> +               return NULL;
> +
> +       match = of_match_node(matches, root);
> +       of_node_put(root);
> +
> +       if (!match)
> +               return NULL;
> +
> +       return match->data;
> +}
> +EXPORT_SYMBOL(of_machine_get_match_data);

These two functions are very similar, but look different.  If the
former would return a pointer instead of a bool, the latter could be
built on top.

Even if you still prefer returning a bool, they could share a common
private helper returning a pointer.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds