Re: [PATCH v5 10/10] iio: dac: adi-axi-dac: add registering of child fdt node

["Nuno Sá" <noname.nuno@gmail.com>]

On Tue, 2024-10-08 at 17:43 +0200, 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.
> 
> The DAC device is defined as a child node of the backend.
> Registering the child fdt node as a platform devices.
> 
> Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>
> ---
>  drivers/iio/dac/adi-axi-dac.c | 61
> +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 61 insertions(+)
> 
> diff --git a/drivers/iio/dac/adi-axi-dac.c b/drivers/iio/dac/adi-axi-dac.c
> index e43d0ecccb50..754c4061d0e3 100644
> --- a/drivers/iio/dac/adi-axi-dac.c
> +++ b/drivers/iio/dac/adi-axi-dac.c
> @@ -18,6 +18,7 @@
>  #include <linux/module.h>
>  #include <linux/mod_devicetable.h>
>  #include <linux/mutex.h>
> +#include <linux/platform_data/ad3552r-hs.h>
>  #include <linux/platform_device.h>
>  #include <linux/property.h>
>  #include <linux/regmap.h>
> @@ -108,6 +109,8 @@ struct axi_dac_info {
>  struct axi_dac_state {
>  	struct regmap *regmap;
>  	struct device *dev;
> +	/* Target DAC platform device */
> +	struct platform_device *dac_pdev;
>  	/*
>  	 * lock to protect multiple accesses to the device registers and
> global
>  	 * data/variables.
> @@ -750,6 +753,44 @@ static int axi_dac_bus_reg_read(struct iio_backend *back,
> u32 reg, u32 *val,
>  	return regmap_read(st->regmap, AXI_DAC_CUSTOM_RD_REG, val);
>  }
>  
> +static void axi_dac_child_remove(void *data)
> +{
> +	struct axi_dac_state *st = data;
> +
> +	platform_device_unregister(st->dac_pdev);
> +}
> +
> +static int axi_dac_create_platform_device(struct axi_dac_state *st,
> +					  struct fwnode_handle *child)
> +{
> +	struct ad3552r_hs_platform_data pdata = {
> +		.bus_reg_read = axi_dac_bus_reg_read,
> +		.bus_reg_write = axi_dac_bus_reg_write,
> +	};
> +	struct platform_device_info pi = {
> +		.parent = st->dev,
> +		.name = fwnode_get_name(child),
> +		.id = PLATFORM_DEVID_AUTO,
> +		.fwnode = child,
> +		.data = &pdata,
> +		.size_data = sizeof(pdata),
> +	};
> +	struct platform_device *pdev;
> +	int ret;
> +
> +	pdev = platform_device_register_full(&pi);
> +	if (IS_ERR(pdev))
> +		return PTR_ERR(pdev);
> +
> +	st->dac_pdev = pdev;

Don't need to save it in the state struct. Pass it directly to
devm_add_action_or_reset()

> +
> +	ret = devm_add_action_or_reset(st->dev, axi_dac_child_remove, st);
> +	if (ret)
> +		return ret;
> +
> +	return 0;

return devm_add_action_or_reset();

> +}
> +
>  static const struct iio_backend_ops axi_dac_generic_ops = {
>  	.enable = axi_dac_enable,
>  	.disable = axi_dac_disable,
> @@ -886,6 +927,26 @@ static int axi_dac_probe(struct platform_device *pdev)
>  		return dev_err_probe(&pdev->dev, ret,
>  				     "failed to register iio backend\n");
>  
> +	if (st->info->bus_controller) {

I guess for now all child nodes that the IP has are for this usecase so I would
just assume it and drop the bus_controller. Let's deal with something different
when the usecase for it pops up. In any case, the flag is only needed in this
patch so it should only be introduced now.

> +		device_for_each_child_node_scoped(&pdev->dev, child) {
> +			int val;
> +
> +			/* Processing only reg 0 node */
> +			ret = fwnode_property_read_u32(child, "reg", &val);
> +			if (ret || val != 0)
> +				continue;

The conditions are not really related so I would not mix them:
if (ret)
	return dev_err_probe(); // some logs might be helpful...
if (val > 0)
	return dev_err_probe();
> +
> +			ret = fwnode_property_read_u32(child, "io-backends",
> +						       &val);
> +			if (ret)
> +				continue;

The above looks redundant...
> +
> +			ret = axi_dac_create_platform_device(st, child);
> +			if (ret)
> +				continue;

Should we really ignore all errors?
> +		}
> +	}
> +
>  	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),
>