Re: [RFC PATCH v2 1/5] leds: trigger: add API for HW offloading of triggers

From: Andrew Lunn <andrew@lunn.ch>
To: Ansuel Smith <ansuelsmth@gmail.com>
Cc: "Vivien Didelot" <vivien.didelot@gmail.com>,
	"Florian Fainelli" <f.fainelli@gmail.com>,
	"Vladimir Oltean" <olteanv@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Jonathan Corbet" <corbet@lwn.net>, "Pavel Machek" <pavel@ucw.cz>,
	"John Crispin" <john@phrozen.org>,
	netdev@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-leds@vger.kernel.org, "Marek Behún" <kabel@kernel.org>
Subject: Re: [RFC PATCH v2 1/5] leds: trigger: add API for HW offloading of triggers
Date: Mon, 8 Nov 2021 15:04:23 +0100	[thread overview]
Message-ID: <YYkuZwQi66slgfTZ@lunn.ch> (raw)
In-Reply-To: <20211108002500.19115-2-ansuelsmth@gmail.com>

> +static inline int led_trigger_offload(struct led_classdev *led_cdev)
> +{
> +	int ret;
> +
> +	if (!led_cdev->trigger_offload)
> +		return -EOPNOTSUPP;
> +
> +	ret = led_cdev->trigger_offload(led_cdev, true);
> +	led_cdev->offloaded = !ret;
> +
> +	return ret;
> +}
> +
> +static inline void led_trigger_offload_stop(struct led_classdev *led_cdev)
> +{
> +	if (!led_cdev->trigger_offload)
> +		return;
> +
> +	if (led_cdev->offloaded) {
> +		led_cdev->trigger_offload(led_cdev, false);
> +		led_cdev->offloaded = false;
> +	}
> +}
> +#endif

I think there should be two calls into the cdev driver, not this
true/false parameter. trigger_offload_start() and
trigger_offload_stop().

There are also a number of PHYs which don't allow software blinking of
the LED. So for them, trigger_offload_stop() is going to return
-EOPNOTSUPP. And you need to handle that correctly.

It would be go to also document the expectations of
trigger_offload_stop(). Should it leave the LED in whatever state it
was, or force it off? 

     Andrew