linux-kernel - Re: [PATCH v3 3/3] leds: trigger: implement a tty trigger

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Message-ID: <b2844f63-d580-ddc2-b4ed-817eaa89a2c6@gmail.com>
Date:   Tue, 17 Dec 2019 21:27:13 +0100
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc:     Pavel Machek <pavel@....cz>, Dan Murphy <dmurphy@...com>,
        Jiri Slaby <jslaby@...e.com>, kernel@...gutronix.de,
        linux-kernel@...r.kernel.org, linux-leds@...r.kernel.org,
        linux-serial@...r.kernel.org
Subject: Re: [PATCH v3 3/3] leds: trigger: implement a tty trigger

On 12/17/19 6:21 PM, Greg Kroah-Hartman wrote:
> On Tue, Dec 17, 2019 at 05:23:13PM +0100, Uwe Kleine-König wrote:
>> On Tue, Dec 17, 2019 at 04:27:24PM +0100, Greg Kroah-Hartman wrote:
>>> On Tue, Dec 17, 2019 at 04:07:36PM +0100, Uwe Kleine-König wrote:
>>>> Usage is as follows:
>>>>
>>>> 	myled=ledname
>>>> 	tty=ttyS0
>>>>
>>>> 	echo tty > /sys/class/leds/$myled/trigger
>>>> 	cat /sys/class/tty/$tty/dev > /sys/class/leds/$myled/dev
>>>
>>> Is this the correct instructions?  Aren't you looking for a major/minor
>>> number instead in your sysfs file?
>>
>> This is correct, yes, at least it works as intended on my machine.
>>
>> /sys/class/tty/$tty/dev produces $major:$minor and that's what the
>> led-trigger consumes.
> 
> Ugh, nevermind, I totally read that wrong, I was thinking "echo" instead
> of cat.  My fault, what you wrote is correct.  Should that be documented
> somewhere in a Documentation/ABI/ file so that people know how to use
> this new sysfs file?  How are led triggers documented?

LED triggers have their corresponding entries in Documentation/ABI.

Uwe, you already did that for netdev trigger:

Documentation/ABI/testing/sysfs-class-led-trigger-netdev

It would be nice to have one for this too.

There are also less formal docs in Documentation/leds, e.g.:

Documentation/leds/ledtrig-usbport.rst

-- 
Best regards,
Jacek Anaszewski