linux-kernel - Re: [PATCH v2 2/3] iio: adc: xilinx-ams: use device

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Message-ID: <20240810113855.691dfb6d@jic23-huawei>
Date: Sat, 10 Aug 2024 11:38:55 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Javier Carrasco <javier.carrasco.cruz@...il.com>
Cc: Suzuki K Poulose <suzuki.poulose@....com>, Mike Leach
 <mike.leach@...aro.org>, James Clark <james.clark@...aro.org>, Alexander
 Shishkin <alexander.shishkin@...ux.intel.com>, Michael Hennerich
 <Michael.Hennerich@...log.com>, Lars-Peter Clausen <lars@...afoo.de>, Anand
 Ashok Dumbre <anand.ashok.dumbre@...inx.com>, Michal Simek
 <michal.simek@....com>, Sakari Ailus <sakari.ailus@...ux.intel.com>, Pavel
 Machek <pavel@....cz>, Lee Jones <lee@...nel.org>,
 coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
 linux-leds@...r.kernel.org
Subject: Re: [PATCH v2 2/3] iio: adc: xilinx-ams: use device_* to iterate
 over device child nodes

On Thu, 08 Aug 2024 17:12:38 +0200
Javier Carrasco <javier.carrasco.cruz@...il.com> wrote:

> Use `device_for_each_child_node_scoped()` in `ams_parse_firmware()`
> to explicitly state device child node access, and simplify the child
> node handling as it is not required outside the loop.
> 
> Signed-off-by: Javier Carrasco <javier.carrasco.cruz@...il.com>

One follow up question for those familiar with the driver.
Why do we check if the main device is available?
	if (fwnode_device_is_available(fwnode)) {
		ret = ams_init_module(indio_dev, fwnode, ams_channels);
		if (ret < 0)
			return ret;

		num_channels += ret;
	}


How is the platform device driver probed if it's not available?

Jonathan


> ---
>  drivers/iio/adc/xilinx-ams.c | 15 +++++----------
>  1 file changed, 5 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/iio/adc/xilinx-ams.c b/drivers/iio/adc/xilinx-ams.c
> index f051358d6b50..ebc583b07e0c 100644
> --- a/drivers/iio/adc/xilinx-ams.c
> +++ b/drivers/iio/adc/xilinx-ams.c
> @@ -1275,7 +1275,6 @@ static int ams_parse_firmware(struct iio_dev *indio_dev)
>  	struct ams *ams = iio_priv(indio_dev);
>  	struct iio_chan_spec *ams_channels, *dev_channels;
>  	struct device *dev = indio_dev->dev.parent;
> -	struct fwnode_handle *child = NULL;
>  	struct fwnode_handle *fwnode = dev_fwnode(dev);
>  	size_t ams_size;
>  	int ret, ch_cnt = 0, i, rising_off, falling_off;
> @@ -1297,16 +1296,12 @@ static int ams_parse_firmware(struct iio_dev *indio_dev)
>  		num_channels += ret;
>  	}
>  
> -	fwnode_for_each_child_node(fwnode, child) {
> -		if (fwnode_device_is_available(child)) {
> -			ret = ams_init_module(indio_dev, child, ams_channels + num_channels);
> -			if (ret < 0) {
> -				fwnode_handle_put(child);
> -				return ret;
> -			}
> +	device_for_each_child_node_scoped(dev, child) {
> +		ret = ams_init_module(indio_dev, child, ams_channels + num_channels);
> +		if (ret < 0)
> +			return ret;
>  
> -			num_channels += ret;
> -		}
> +		num_channels += ret;
>  	}
>  
>  	for (i = 0; i < num_channels; i++) {
>