linux-kernel - Re: [RFC PATCH v6 02/11] leds: add function to configure hardware controlled LED

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Message-ID: <YnMK+EZDQXSGDXM1@lunn.ch>
Date:   Thu, 5 May 2022 01:23:36 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Ansuel Smith <ansuelsmth@...il.com>
Cc:     Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Jonathan Corbet <corbet@....net>, Pavel Machek <pavel@....cz>,
        John Crispin <john@...ozen.org>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-leds@...r.kernel.org
Subject: Re: [RFC PATCH v6 02/11] leds: add function to configure hardware
 controlled LED

> +In SUPPORTED hw_control_configure() should return 0 or 1 if the LED driver supports the
> +requested blink mode (flags) or not.

-EOPNOTSUPP might be clearer.


> +In ZERO hw_control_configure() should return 0 with success operation or error.
> +
> +The unsigned long flag is specific to the trigger and change across them. It's in the LED
> +driver interest know how to elaborate this flag and to declare support for a
> +particular trigger. For this exact reason explicit support for the specific
> +trigger is mandatory or the driver returns -EOPNOTSUPP if asked to enter offload mode
> +with a not supported trigger.
> +If the driver returns -EOPNOTSUPP on hw_control_configure(), the trigger activation will
> +fail as the driver doesn't support that specific offload trigger or doesn't know
> +how to handle the provided flags.
> +
>  Known Issues
>  ============
>  
> diff --git a/include/linux/leds.h b/include/linux/leds.h
> index 09ff1dc6f48d..b5aad67fecfb 100644
> --- a/include/linux/leds.h
> +++ b/include/linux/leds.h
> @@ -73,6 +73,16 @@ enum led_blink_modes {
>  	SOFTWARE_HARDWARE_CONTROLLED,
>  };
>  
> +#ifdef CONFIG_LEDS_HARDWARE_CONTROL
> +enum blink_mode_cmd {
> +	BLINK_MODE_ENABLE, /* Enable the hardware blink mode */
> +	BLINK_MODE_DISABLE, /* Disable the hardware blink mode */
> +	BLINK_MODE_READ, /* Read the status of the hardware blink mode */
> +	BLINK_MODE_SUPPORTED, /* Ask the driver if the hardware blink mode is supported */
> +	BLINK_MODE_ZERO, /* Disable any hardware blink active */
> +};
> +#endif

Skip the #ifdef. The enum itself takes no space if never used, and it
makes the driver simpler if they always exist.

> +
>  struct led_classdev {
>  	const char		*name;
>  	unsigned int brightness;
> @@ -185,6 +195,17 @@ struct led_classdev {
>  	 * the old status but that is not mandatory and also putting it off is accepted.
>  	 */
>  	int			(*hw_control_stop)(struct led_classdev *led_cdev);
> +	/* This will be used to configure the various blink modes LED support in hardware
> +	 * mode.
> +	 * The LED driver require to support the active trigger and will elaborate the
> +	 * unsigned long flag and do the operation based on the provided cmd.
> +	 * Current operation are enable,disable,supported and status.
> +	 * A trigger will use this to enable or disable the asked blink mode, check the
> +	 * status of the blink mode or ask if the blink mode can run in hardware mode.
> +	 */
> +	int			(*hw_control_configure)(struct led_classdev *led_cdev,
> +							unsigned long flag,
> +							enum blink_mode_cmd cmd);
>  #endif
>  #endif
>  
> @@ -454,6 +475,24 @@ static inline void *led_get_trigger_data(struct led_classdev *led_cdev)
>  	return led_cdev->trigger_data;
>  }
>  
> +#ifdef CONFIG_LEDS_HARDWARE_CONTROL
> +static inline bool led_trigger_blink_mode_is_supported(struct led_classdev *led_cdev,
> +						       unsigned long flag)
> +{
> +	int ret;
> +
> +	/* Sanity check: make sure led support hw mode */
> +	if (led_cdev->blink_mode == SOFTWARE_CONTROLLED)
> +		return false;
> +
> +	ret = led_cdev->hw_control_configure(led_cdev, flag, BLINK_MODE_SUPPORTED);
> +	if (ret > 0)
> +		return true;
> +
> +	return false;
> +}
> +#endif

Please add a version which returns false when
CONFIG_LEDS_HARDWARE_CONTROL is disabled.

Does this actually need to be an inline function?

     Andrew