linux-kernel - Re: [PATCH 1/2] mfd: core: Support multiple OF child devices of the same type

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Message-ID: <20190605063108.GF4797@dell>
Date:   Wed, 5 Jun 2019 07:31:08 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Robert Hancock <hancock@...systems.ca>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] mfd: core: Support multiple OF child devices of the
 same type

On Tue, 04 Jun 2019, Robert Hancock wrote:

> Previously the MFD core supported assigning OF nodes to created MFD
> devices, but relied solely on matching the of_compatible string. This
> would result in devices being potentially assigned the wrong node if
> there are multiple devices with the same compatible string within a
> multifunction device.
> 
> Add support for matching the full name of the node in the MFD cell
> definition, so that we can match against a specific instance of a
> device. If this is not specified, we match just based on the
> compatible string, as before.
> 
> Signed-off-by: Robert Hancock <hancock@...systems.ca>
> ---
>  drivers/mfd/mfd-core.c   | 5 ++++-
>  include/linux/mfd/core.h | 3 +++
>  2 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c
> index 1ade4c8..74bc895 100644
> --- a/drivers/mfd/mfd-core.c
> +++ b/drivers/mfd/mfd-core.c
> @@ -177,7 +177,10 @@ static int mfd_add_device(struct device *parent, int id,
>  
>  	if (parent->of_node && cell->of_compatible) {
>  		for_each_child_of_node(parent->of_node, np) {
> -			if (of_device_is_compatible(np, cell->of_compatible)) {
> +			if (of_device_is_compatible(np, cell->of_compatible) &&
> +			    (!cell->of_full_name ||
> +			     !strcmp(cell->of_full_name,
> +				     of_node_full_name(np)))) {
>  				pdev->dev.of_node = np;
>  				break;

That is some ugly, squashed up code.

If we end up accepting this, I suggest flattening this out a bit.

... but we'll cross that bridge when we come to it.

> diff --git a/include/linux/mfd/core.h b/include/linux/mfd/core.h
> index 99c0395..470f6cb 100644
> --- a/include/linux/mfd/core.h
> +++ b/include/linux/mfd/core.h
> @@ -55,6 +55,9 @@ struct mfd_cell {
>  	 */
>  	const char		*of_compatible;
>  
> +	/* Optionally match against a specific device of a given type */
> +	const char		*of_full_name;
> +

Can you give me an example for when this might be useful?

>  	/* Matches ACPI */
>  	const struct mfd_cell_acpi_match	*acpi_match;
>  

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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