linux-kernel - Re: [PATCH v2 6/6] gpiolib: add support for software nodes

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Date:   Wed, 9 Nov 2022 13:20:46 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        linux-acpi@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 6/6] gpiolib: add support for software nodes

On Tue, Nov 08, 2022 at 04:26:51PM -0800, Dmitry Torokhov wrote:
> Now that static device properties understand notion of child nodes and
> references, let's teach gpiolib to handle them:
> 
> - GPIOs are represented as a references to software nodes representing
>   gpiochip
> - references must have 2 arguments - GPIO number within the chip and
>   GPIO flags (GPIO_ACTIVE_LOW/GPIO_ACTIVE_HIGH, etc)
> - a new PROPERTY_ENTRY_GPIO() macro is supplied to ensure the above
> - name of the software node representing gpiochip must match label of
>   the gpiochip, as we use it to locate gpiochip structure at runtime
> 
> The following illustrates use of software nodes to describe a "System"
> button that is currently specified via use of gpio_keys_platform_data
> in arch/mips/alchemy/board-mtx1.c. It follows bindings specified in
> Documentation/devicetree/bindings/input/gpio-keys.yaml.
> 
> static const struct software_node mxt1_gpiochip2_node = {
> 	.name = "alchemy-gpio2",
> };
> 
> static const struct property_entry mtx1_gpio_button_props[] = {
> 	PROPERTY_ENTRY_U32("linux,code", BTN_0),
> 	PROPERTY_ENTRY_STRING("label", "System button"),
> 	PROPERTY_ENTRY_GPIO("gpios", &mxt1_gpiochip2_node, 7, GPIO_ACTIVE_LOW),
> 	{ }
> };
> 
> Similarly, arch/arm/mach-tegra/board-paz00.c can be converted to:
> 
> static const struct software_node tegra_gpiochip_node = {
> 	.name = "tegra-gpio",
> };
> 
> static struct property_entry wifi_rfkill_prop[] __initdata = {
> 	PROPERTY_ENTRY_STRING("name", "wifi_rfkill"),
> 	PROPERTY_ENTRY_STRING("type", "wlan"),
> 	PROPERTY_ENTRY_GPIO("reset-gpios",
> 			    &tegra_gpiochip_node, 25, GPIO_ACTIVE_HIGH);
> 	PROPERTY_ENTRY_GPIO("shutdown-gpios",
> 			    &tegra_gpiochip_node, 85, GPIO_ACTIVE_HIGH);
> 	{ },
> };
> 
> static struct platform_device wifi_rfkill_device = {
> 	.name	= "rfkill_gpio",
> 	.id	= -1,
> };
> 
> ...
> 
> 	software_node_register(&tegra_gpiochip_node);
> 	device_create_managed_software_node(&wifi_rfkill_device.dev,
> 					    wifi_rfkill_prop, NULL);

...

> +static struct gpio_chip *swnode_get_chip(struct fwnode_handle *fwnode)
> +{
> +	const struct software_node *chip_node;
> +	struct gpio_chip *chip;
> +
> +	chip_node = to_software_node(fwnode);
> +	if (!chip_node || !chip_node->name)
> +		return ERR_PTR(-EINVAL);

> +	chip = gpiochip_find((void *)chip_node->name,
> +			     swnode_gpiochip_match_name);

One line?

> +	if (!chip)
> +		return ERR_PTR(-EPROBE_DEFER);
> +
> +	return chip;

As below you can use Elvis here as well, up to you.

	return chip ?: ERR_PTR(...);

> +}

...

> +	desc = gpiochip_get_desc(chip, args.args[0]);
> +	*flags = args.args[1]; /* We expect native GPIO flags */
> +
> +	pr_debug("%s: parsed '%s' property of node '%pfwP[%d]' - status (%d)\n",
> +		 __func__, propname, fwnode, idx, PTR_ERR_OR_ZERO(desc));

%pe ?

> +	return desc;

...

> +	while (fwnode_property_get_reference_args(fwnode, propname, NULL,
> +						  0, count, &args) == 0) {

I would move 0 to the previous line.

> +		fwnode_handle_put(args.fwnode);
> +		count++;
> +	}

...

>  int gpiod_count(struct device *dev, const char *con_id)
>  {
> -	const struct fwnode_handle *fwnode = dev ? dev_fwnode(dev) : NULL;
> -	int count = -ENOENT;
> +	struct fwnode_handle *fwnode = dev ? dev_fwnode(dev) : NULL;

Why dropping const?

> +	int count;

Why this change is needed?

>  	if (is_of_node(fwnode))
>  		count = of_gpio_get_count(dev, con_id);
>  	else if (is_acpi_node(fwnode))
>  		count = acpi_gpio_count(dev, con_id);
> +	else if (is_software_node(fwnode))
> +		count = swnode_gpio_count(fwnode, con_id);
> +	else
> +		count = -ENOENT;

...

> +#include <dt-bindings/gpio/gpio.h>

Not sure why we have this here.

> +#include <linux/property.h>
> +
> +#define PROPERTY_ENTRY_GPIO(_name_, _chip_node_, _idx_, _flags_) \
> +	PROPERTY_ENTRY_REF(_name_, _chip_node_, _idx_, _flags_)

-- 
With Best Regards,
Andy Shevchenko