linux-kernel - Re: [PATCH v6 8/8] iio: dac: adi-axi-dac: add registering of child fdt node

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Message-ID: <022be235-f028-4b6e-9589-b0066df5d459@baylibre.com>
Date: Mon, 14 Oct 2024 16:16:34 -0500
From: David Lechner <dlechner@...libre.com>
To: Angelo Dureghello <adureghello@...libre.com>, Nuno Sá
 <nuno.sa@...log.com>, Lars-Peter Clausen <lars@...afoo.de>,
 Michael Hennerich <Michael.Hennerich@...log.com>,
 Jonathan Cameron <jic23@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Olivier Moysan <olivier.moysan@...s.st.com>
Cc: linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH v6 8/8] iio: dac: adi-axi-dac: add registering of child
 fdt node

On 10/14/24 5:08 AM, Angelo Dureghello wrote:
> From: Angelo Dureghello <adureghello@...libre.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@...libre.com>
> ---
>  drivers/iio/dac/adi-axi-dac.c | 53 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 53 insertions(+)
> 
> diff --git a/drivers/iio/dac/adi-axi-dac.c b/drivers/iio/dac/adi-axi-dac.c
> index b887c6343f96..f85e3138d428 100644
> --- a/drivers/iio/dac/adi-axi-dac.c
> +++ b/drivers/iio/dac/adi-axi-dac.c
> @@ -29,6 +29,8 @@
>  #include <linux/iio/buffer.h>
>  #include <linux/iio/iio.h>
>  
> +#include "ad3552r-hs.h"
> +
>  /*
>   * Register definitions:
>   *   https://wiki.analog.com/resources/fpga/docs/axi_dac_ip#register_map
> @@ -738,6 +740,39 @@ 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 platform_device *pdev = data;
> +
> +	platform_device_unregister(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;
> +
> +	pdev = platform_device_register_full(&pi);
> +	if (IS_ERR(pdev))
> +		return PTR_ERR(pdev);
> +
> +	device_set_node(&pdev->dev, child);

Not sure why Nuno suggested adding device_set_node(). It is
redundant since platform_device_register_full() already does
the same thing.

(And setting it after platform_device_register_full() would
be too late anyway since drivers may have already probed.)

> +
> +	return devm_add_action_or_reset(st->dev, axi_dac_child_remove, pdev);
> +}
> +
>  static const struct iio_backend_ops axi_dac_generic_ops = {
>  	.enable = axi_dac_enable,
>  	.disable = axi_dac_disable,
> @@ -874,6 +909,24 @@ 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) {
> +		int val;
> +
> +		/* Processing only reg 0 node */
> +		ret = fwnode_property_read_u32(child, "reg", &val);
> +		if (ret)
> +			return dev_err_probe(&pdev->dev, ret,
> +						"child node missing.");

Shouldn't the error message say that there is a problem with the reg
property? We already have a handle to the child node, so the child node
isn't missing.

> +		if (val != 0)
> +			return dev_err_probe(&pdev->dev, -EINVAL,
> +						"invalid node address.");
> +
> +		ret = axi_dac_create_platform_device(st, child);
> +		if (ret)
> +			return dev_err_probe(&pdev->dev, -EINVAL,
> +						"could not create device.");
> +	}
> +
>  	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),
>