linux-kernel - RE: [PATCH] Add LED pattern trigger

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Message-ID: <BLU172-W451DF59115DB2B0A7F694AACC90@phx.gbl>
Date:	Tue, 31 Dec 2013 13:48:50 -0500
From:	Joe Xue <lgxue@...mail.com>
To:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
CC:	"cooloney@...il.com" <cooloney@...il.com>,
	"rpurdie@...ys.net" <rpurdie@...ys.net>,
	"rob@...dley.net" <rob@...dley.net>,
	"milo.kim@...com" <milo.kim@...com>, "pavel@....cz" <pavel@....cz>,
	"linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: RE: [PATCH] Add LED pattern trigger

>> + * Based on Richard Purdie's ledtrig-timer.c and Atsushi Nemoto's
>> + * ledtrig-heartbeat.c and Shuah Khan's ledtrig-transient.c
>
> I stil think this belongs in user space except for platforms with hardware
> acceleration for it.

This can free the user space application from loop or thread.

>> +#define MAX_PATTEN_LEN 255
>
> Arbitary limits that are not needed if it was in userspace, and not it
> seems a sensible one - why not use 256 ?

Yes, will change it to kmalloc


>> +static DEVICE_ATTR(pattern, 0644, pattern_pattern_show, pattern_pattern_store);
>> +static DEVICE_ATTR(delay_unit, 0644,
>> +static void pattern_trig_deactivate(struct led_classdev *led_cdev)
>> +{
>> + struct pattern_trig_data *pattern_data = led_cdev->trigger_data;
>> +
>> + if (led_cdev->activated) {
>> + del_timer_sync(&pattern_data->timer);
>> + device_remove_file(led_cdev->dev, &dev_attr_pattern);
>> + device_remove_file(led_cdev->dev, &dev_attr_delay_unit);
>
> This doesn't as far as I can see do what you think. If I have the file
> currently open then device_remove_file will not remove my existing access
> to it, but you just released the pattern data so I now write to free
> memory.

will add the mutex lock to avoid that 		 	   		  --
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