linux-kernel - Re: [PATCH v1 1/4] backlight: hx8357: Make use of device properties

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Message-ID: <87bk9novmp.fsf@minerva.mail-host-address-is-not-set>
Date: Mon, 15 Jan 2024 09:20:46 +0100
From: Javier Martinez Canillas <javierm@...hat.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Andy Shevchenko
 <andriy.shevchenko@...ux.intel.com>, dri-devel@...ts.freedesktop.org,
 linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: Jingoo Han <jingoohan1@...il.com>, Daniel Thompson
 <daniel.thompson@...aro.org>, Lee Jones <lee@...nel.org>, Helge Deller
 <deller@....de>
Subject: Re: [PATCH v1 1/4] backlight: hx8357: Make use of device properties

Andy Shevchenko <andriy.shevchenko@...ux.intel.com> writes:

Hello Andy,

> Convert the module to be property provider agnostic and allow
> it to be used on non-OF platforms.
>
> Include mod_devicetable.h explicitly to replace the dropped of.h
> which included mod_devicetable.h indirectly.
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  drivers/video/backlight/hx8357.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/video/backlight/hx8357.c b/drivers/video/backlight/hx8357.c
> index bf18337ff0c2..c7fd10d55c5d 100644
> --- a/drivers/video/backlight/hx8357.c
> +++ b/drivers/video/backlight/hx8357.c
> @@ -8,9 +8,9 @@
>  #include <linux/delay.h>
>  #include <linux/gpio/consumer.h>
>  #include <linux/lcd.h>
> +#include <linux/mod_devicetable.h>
>  #include <linux/module.h>
> -#include <linux/of.h>
> -#include <linux/of_device.h>
> +#include <linux/property.h>
>  #include <linux/spi/spi.h>
>  
>  #define HX8357_NUM_IM_PINS	3
> @@ -564,6 +564,8 @@ static struct lcd_ops hx8357_ops = {
>  	.get_power	= hx8357_get_power,
>  };
>  
> +typedef int (*hx8357_init)(struct lcd_device *);
> +

This kind of typedef usage is frowned upon in the Linux coding style [0]
(per my understanding at least) and indeed in my opinion it makes harder
to grep.

[0] https://www.kernel.org/doc/Documentation/process/coding-style.rst

>  static const struct of_device_id hx8357_dt_ids[] = {
>  	{
>  		.compatible = "himax,hx8357",
> @@ -582,7 +584,7 @@ static int hx8357_probe(struct spi_device *spi)
>  	struct device *dev = &spi->dev;
>  	struct lcd_device *lcdev;
>  	struct hx8357_data *lcd;
> -	const struct of_device_id *match;
> +	hx8357_init init;
>  	int i, ret;
>  
>  	lcd = devm_kzalloc(&spi->dev, sizeof(*lcd), GFP_KERNEL);
> @@ -597,8 +599,8 @@ static int hx8357_probe(struct spi_device *spi)
>  
>  	lcd->spi = spi;
>  
> -	match = of_match_device(hx8357_dt_ids, &spi->dev);
> -	if (!match || !match->data)
> +	init = device_get_match_data(dev);
> +	if (!init)
>  		return -EINVAL;
>  
>  	lcd->reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
> @@ -627,7 +629,7 @@ static int hx8357_probe(struct spi_device *spi)
>  
>  	hx8357_lcd_reset(lcdev);
>  
> -	ret = ((int (*)(struct lcd_device *))match->data)(lcdev);

This is what I mean, before it was clear what was stored in match->data.
But after you changes, what is returned by the device_get_match_data()
function is opaque and you need to look at the typedef hx8357_init to
figure that out.

No strong opinion though and I see other drivers doing the same (but no
other driver in drivers/video/backlight).

Reviewed-by: Javier Martinez Canillas <javierm@...hat.com>

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat