Re: [PATCH v2 4/9] iio: backend adi-axi-dac: add registering of child fdt node

[David Lechner <dlechner@baylibre.com>]

On 9/5/24 10:17 AM, Angelo Dureghello wrote:
> From: Angelo Dureghello <adureghello@baylibre.com>
> 
> Change to obtain the fdt use case as reported in the
> adi,ad3552r.yaml file in this patchset, with the DAC device that
> is actually using the backend set as a child node of the backend.
> 
> To obtain this, registering all the child fdt nodes as platform
> devices.
> 
> Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>
> Co-developed-by: David Lechner <dlechner@baylibre.com>
> Co-developed-by: Nuno Sá <nuno.sa@analog.com>
> ---
>  drivers/iio/dac/adi-axi-dac.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/drivers/iio/dac/adi-axi-dac.c b/drivers/iio/dac/adi-axi-dac.c
> index cc31e1dcd1df..e883cd557b6a 100644
> --- a/drivers/iio/dac/adi-axi-dac.c
> +++ b/drivers/iio/dac/adi-axi-dac.c
> @@ -783,6 +783,7 @@ static int axi_dac_probe(struct platform_device *pdev)
>  {
>  	struct axi_dac_state *st;
>  	const struct axi_dac_info *info;
> +	struct platform_device *child_pdev;
>  	void __iomem *base;
>  	unsigned int ver;
>  	struct clk *clk;
> @@ -862,6 +863,20 @@ static int axi_dac_probe(struct platform_device *pdev)
>  		return dev_err_probe(&pdev->dev, ret,
>  				     "failed to register iio backend\n");
>  
> +	device_for_each_child_node_scoped(&pdev->dev, child) {

This should use fwnode_for_each_available_child_node() so that it skips
nodes with status != "okay".

Would be nice to introduce a scoped version of this function too.

Also, if we are allowing multiple devices on the bus, the DT bindings
need to have a reg property that is unique for each child.

> +		struct platform_device_info pi;
> +
> +		memset(&pi, 0, sizeof(pi));

struct platform_device_info pi = { };

avoids the need for memset().

> +
> +		pi.name = fwnode_get_name(child);
> +		pi.id = PLATFORM_DEVID_AUTO;
> +		pi.fwnode = child;

Need to have pi.parent = &pdev->dev;

It could also make sense to have all of the primary bus functions
(reg read/write, ddr enable/disable, etc.) passed here as platform
data instead of having everything go through the IIO backend.

> +
> +		child_pdev = platform_device_register_full(&pi);
> +		if (IS_ERR(child_pdev))
> +			return PTR_ERR(child_pdev);

These devices need to be unregistered on any error return and when
the parent device is removed.

> +	}
> +
>  	dev_info(&pdev->dev, "AXI DAC IP core (%d.%.2d.%c) probed\n",
>  		 ADI_AXI_PCORE_VER_MAJOR(ver),
>  		 ADI_AXI_PCORE_VER_MINOR(ver),
>