linux-kernel - Re: [PATCH v2 1/1] iio: multiplexer: Make use of device properties

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Message-ID: <6df069a3-939d-21be-ed17-bc9e9d20cffc@axentia.se>
Date:   Sun, 27 Feb 2022 03:28:15 +0100
From:   Peter Rosin <peda@...ntia.se>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>
Subject: Re: [PATCH v2 1/1] iio: multiplexer: Make use of device properties

Hi!

Sorry for the late reply.

On 2022-02-02 21:44, Andy Shevchenko wrote:
> Convert the module to be property provider agnostic and allow
> it to be used on non-OF platforms.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
> v2: dropped depends on OF
>  drivers/iio/multiplexer/Kconfig   |  1 -
>  drivers/iio/multiplexer/iio-mux.c | 48 ++++++++++++++-----------------
>  2 files changed, 22 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/iio/multiplexer/Kconfig b/drivers/iio/multiplexer/Kconfig
> index a1e1332d1206..928f424a1ed3 100644
> --- a/drivers/iio/multiplexer/Kconfig
> +++ b/drivers/iio/multiplexer/Kconfig
> @@ -9,7 +9,6 @@ menu "Multiplexers"
>  config IIO_MUX
>  	tristate "IIO multiplexer driver"
>  	select MULTIPLEXER
> -	depends on OF || COMPILE_TEST
>  	help
>  	  Say yes here to build support for the IIO multiplexer.
>  
> diff --git a/drivers/iio/multiplexer/iio-mux.c b/drivers/iio/multiplexer/iio-mux.c
> index f422d44377df..e6f0fef96494 100644
> --- a/drivers/iio/multiplexer/iio-mux.c
> +++ b/drivers/iio/multiplexer/iio-mux.c
> @@ -10,11 +10,12 @@
>  #include <linux/err.h>
>  #include <linux/iio/consumer.h>
>  #include <linux/iio/iio.h>
> +#include <linux/mod_devicetable.h>
>  #include <linux/module.h>
>  #include <linux/mutex.h>
>  #include <linux/mux/consumer.h>
> -#include <linux/of.h>
>  #include <linux/platform_device.h>
> +#include <linux/property.h>
>  
>  struct mux_ext_info_cache {
>  	char *data;
> @@ -324,37 +325,20 @@ static int mux_configure_channel(struct device *dev, struct mux *mux,
>  	return 0;
>  }
>  
> -/*
> - * Same as of_property_for_each_string(), but also keeps track of the
> - * index of each string.
> - */
> -#define of_property_for_each_string_index(np, propname, prop, s, i)	\
> -	for (prop = of_find_property(np, propname, NULL),		\
> -	     s = of_prop_next_string(prop, NULL),			\
> -	     i = 0;							\
> -	     s;								\
> -	     s = of_prop_next_string(prop, s),				\
> -	     i++)
> -
>  static int mux_probe(struct platform_device *pdev)
>  {
>  	struct device *dev = &pdev->dev;
> -	struct device_node *np = pdev->dev.of_node;
>  	struct iio_dev *indio_dev;
>  	struct iio_channel *parent;
>  	struct mux *mux;
> -	struct property *prop;
> -	const char *label;
> +	const char **labels;
>  	u32 state;
> +	int children, all_children;

I dislike that the pattern with one declaration per line is broken here.
There are perhaps a few too many variables, but introducing one instance
of two declarations on one line is disturbing for me.

So, with that fixed,

Acked-by: Peter Rosin <peda@...ntia.se>

>  	int sizeof_ext_info;
> -	int children;
>  	int sizeof_priv;
>  	int i;
>  	int ret;
>  
> -	if (!np)
> -		return -ENODEV;
> -
>  	parent = devm_iio_channel_get(dev, "parent");
>  	if (IS_ERR(parent))
>  		return dev_err_probe(dev, PTR_ERR(parent),
> @@ -366,9 +350,21 @@ static int mux_probe(struct platform_device *pdev)
>  		sizeof_ext_info *= sizeof(*mux->ext_info);
>  	}
>  
> +	all_children = device_property_count_string_array(dev, "channels");
> +	if (all_children < 0)
> +		return all_children;
> +
> +	labels = devm_kmalloc_array(dev, all_children, sizeof(char *), GFP_KERNEL);

I'm a bit sad to see the copy of the labels array. No big deal,
but it seems inelegant. But the of_property_for_each_string_index
macro was also misplaced and therefore inelegant. My guess is
that the device properties should be fairly static and that the
copy is a waste?

So, anyway, I'm just whining here, and the labels copy is ok.

Cheers,
Peter

> +	if (!labels)
> +		return -ENOMEM;
> +
> +	ret = device_property_read_string_array(dev, "channels", labels, all_children);
> +	if (ret < 0)
> +		return ret;
> +
>  	children = 0;
> -	of_property_for_each_string(np, "channels", prop, label) {
> -		if (*label)
> +	for (state = 0; state < all_children; state++) {
> +		if (*labels[state])
>  			children++;
>  	}
>  	if (children <= 0) {
> @@ -395,7 +391,7 @@ static int mux_probe(struct platform_device *pdev)
>  	mux->cached_state = -1;
>  
>  	mux->delay_us = 0;
> -	of_property_read_u32(np, "settle-time-us", &mux->delay_us);
> +	device_property_read_u32(dev, "settle-time-us", &mux->delay_us);
>  
>  	indio_dev->name = dev_name(dev);
>  	indio_dev->info = &mux_info;
> @@ -426,11 +422,11 @@ static int mux_probe(struct platform_device *pdev)
>  	}
>  
>  	i = 0;
> -	of_property_for_each_string_index(np, "channels", prop, label, state) {
> -		if (!*label)
> +	for (state = 0; state < all_children; state++) {
> +		if (!*labels[state])
>  			continue;
>  
> -		ret = mux_configure_channel(dev, mux, state, label, i++);
> +		ret = mux_configure_channel(dev, mux, state, labels[state], i++);
>  		if (ret < 0)
>  			return ret;
>  	}