Re: [PATCH 3/8] deep-probe: skip on-demand platform dev creation for nodes without compatible

[Sascha Hauer <sha@pengutronix.de>]

On Mon, Nov 27, 2023 at 07:35:54AM +0100, Ahmad Fatoum wrote:
> of_device_create_on_demand won't create a new device if the device tree
> node already has a device associated. What it will do however, is to
> create devices for all parent nodes in the device tree if they don't
> already exist. This is unnecessary and clutters the device list
> with nodes that won't ever be matched as they lack a compatible anyway.
> For example a reference to scmi_reg11 in below snippet:
> 
>   &{scmi/protocol@17} {
>       reg = <0x17>;
>       regulators {
>           #address-cells = <0x1>;
>           #size-cells = <0x0>;
>           scmi_reg11: regulator@0 {
>               reg = <0x0>;
>               regulator-name = "reg11";
>           };
>       };
>   };
> 
> will result in creation of a device for the regulators node that serves
> no purpose whatsoever:
> 
>   `-- firmware.of
>      `-- firmware:scmi.of
>         `-- scmi_dev0
>            `-- firmware:scmi:protocol@17:regulators.of
> 
> Avoid this by creating devices on demand only if they have a compatible.

How will this change affect the device hierarchy? When a parent device
node doesn't have a compatible, will the child device then be a child
of its grandparent, or will it just have no parent at all?

Sascha

> 
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
>  drivers/of/platform.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index 9e592d567cae..9ba4438812c1 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -442,9 +442,6 @@ static struct device *of_device_create_on_demand(struct device_node *np)
>  	if (!np->dev && parent->dev)
>  		device_rescan(parent->dev);
>  
> -	if (!np->dev)
> -		pr_debug("Creating device for %pOF\n", np);
> -
>  	/* Create all parent devices needed for the requested device */
>  	parent_dev = parent->dev ? : of_device_create_on_demand(parent);
>  	if (IS_ERR(parent_dev))
> @@ -458,6 +455,11 @@ static struct device *of_device_create_on_demand(struct device_node *np)
>  	if (np->dev)
>  		return np->dev;
>  
> +	if (!of_property_present(np, "compatible"))
> +		return NULL;
> +
> +	pr_debug("Creating device for %pOF\n", np);
> +
>  	if (of_device_is_compatible(np, "arm,primecell"))
>  		dev = of_amba_device_create(np);
>  	else
> -- 
> 2.39.2
> 
> 
> 

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