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

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Date:   Thu, 5 May 2022 15:02:48 +0200
From:   Ansuel Smith <ansuelsmth@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
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

On Thu, May 05, 2022 at 01:23:36AM +0200, Andrew Lunn wrote:
> > +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?

Not at all... Originally it was a smaller function. Will drop it.

>
>      Andrew

-- 
	Ansuel