linux-kernel - Re: [PATCH v20 03/17] leds: multicolor: Introduce a multicolor class definition

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Date:   Tue, 28 Apr 2020 10:41:59 +0200
From:   Pavel Machek <pavel@....cz>
To:     Dan Murphy <dmurphy@...com>
Cc:     jacek.anaszewski@...il.com, linux-leds@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v20 03/17] leds: multicolor: Introduce a multicolor class
 definition

Hi!

> >>+cat /sys/class/leds/multicolor:status/multi_led_index
> >>+green blue red
> >Hmm. We should really make sure LEDs are ordered as "red green
> >blue". Yes, userspace should support any order, but...
> 
> Ordering is not guaranteed since it is based on the DT ordering. I don't
> think we can mandate that these LEDs be put in order in the DT.
> 
> Besides the framework and the device driver do not care what color is where
> only the user space needs to care.  The FW and device driver only care about
> the brightness, intensity and channel.

Ok, lets keep it like this.

> >>+		offset += nrchars;
> >>+	}
> >This checks for "not enough" intensities. Do we need check for "too
> >many" intensities?
> 
> We ignore anything greater then mcled_cdev->num_colors.  So if this is set
> to 3 we only read the first 3 values.
> 
> So we cannot read more then what is set by the DT.

Please make it return an error if extra values are passed in.

> >>+static ssize_t multi_led_intensity_show(struct device *dev,
> >>+			      struct device_attribute *intensity_attr,
> >>+			      char *buf)
> >>+{
> >>+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
> >>+	struct led_classdev_mc *mcled_cdev = lcdev_to_mccdev(led_cdev);
> >>+	int len = 0;
> >>+	int i;
> >>+
> >>+	for (i = 0; i < mcled_cdev->num_colors; i++)
> >>+		len += sprintf(buf + len, "%d ",
> >>+			    mcled_cdev->multicolor_info[i].color_led_intensity);
> >>+
> >>+	len += sprintf(buf + len, "%s", "\n");
> >This will result in extra " " before end of line.
> >
> >Please don't use "%s", "\n" to add single character. "\n" would be enough.
> Ack changed to just sprintf(buf + len, "\n");

Also note the extra space before end of line.

Best regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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