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

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Message-ID: <86ad555f-671a-cb0e-6000-30580f688be1@gmail.com>
Date:   Wed, 18 Dec 2019 22:33:56 +0100
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Pavel Machek <pavel@....cz>, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org, Dan Murphy <dmurphy@...com>,
        kernel@...gutronix.de, Jiri Slaby <jslaby@...e.com>,
        linux-leds@...r.kernel.org
Subject: Re: [PATCH v3 3/3] leds: trigger: implement a tty trigger

On 12/17/19 10:08 PM, Uwe Kleine-König wrote:
> On Tue, Dec 17, 2019 at 09:27:13PM +0100, Jacek Anaszewski wrote:
>> 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
> 
> I'd put into Documentation/ABI/testing/sysfs-class-led-trigger-tty:
> 
> 	What:           /sys/class/leds/<led>/dev
> 	Date:           Dec 2019
> 	KernelVersion:  5.6
> 	Contact:        linux-leds@...r.kernel.org
> 	Description:
> 			Specifies $major:$minor of the triggering tty

Yes, that should be fine.

-- 
Best regards,
Jacek Anaszewski