From: Dan Murphy <dmurphy@ti.com>
To: Jacek Anaszewski <jacek.anaszewski@gmail.com>,
Akinobu Mita <akinobu.mita@gmail.com>,
<linux-leds@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Pavel Machek <pavel@ucw.cz>
Subject: Re: [PATCH -next 2/2] leds: add /sys/class/leds/<led>/current-trigger
Date: Wed, 2 Oct 2019 12:57:01 -0500 [thread overview]
Message-ID: <79102915-5510-40e7-b4be-073e1c85bda6@ti.com> (raw)
In-Reply-To: <589ba4d7-31f5-c789-d5ca-c13650cf5b03@gmail.com>
Jacek
On 10/2/19 12:46 PM, Jacek Anaszewski wrote:
> Dan,
>
> On 10/2/19 5:47 PM, Dan Murphy wrote:
>> Akinobu
>>
>> On 10/2/19 10:13 AM, Akinobu Mita wrote:
>>> Reading /sys/class/leds/<led>/trigger returns all available LED triggers.
>>> However, this violates the "one value per file" rule of sysfs.
>>>
>>> This provides /sys/class/leds/<led>/current-trigger which is almost
>>> identical to /sys/class/leds/<led>/trigger. The only difference is that
>>> 'current-trigger' only shows the current trigger name.
>>>
>>> This new file follows the "one value per file" rule of sysfs.
>>> We can find all available LED triggers by listing the
>>> /sys/devices/virtual/led-trigger/ directory.
>>>
>>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
>>> Cc: Jacek Anaszewski <jacek.anaszewski@gmail.com>
>>> Cc: Pavel Machek <pavel@ucw.cz>
>>> Cc: Dan Murphy <dmurphy@ti.com>
>>> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
>>> ---
>>> Documentation/ABI/testing/sysfs-class-led | 13 +++++++++++
>>> drivers/leds/led-class.c | 10 ++++++++
>>> drivers/leds/led-triggers.c | 38
>>> +++++++++++++++++++++++++++----
>>> drivers/leds/leds.h | 5 ++++
>>> 4 files changed, 62 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/Documentation/ABI/testing/sysfs-class-led
>>> b/Documentation/ABI/testing/sysfs-class-led
>>> index 5f67f7a..fdfed3f 100644
>>> --- a/Documentation/ABI/testing/sysfs-class-led
>>> +++ b/Documentation/ABI/testing/sysfs-class-led
>>> @@ -61,3 +61,16 @@ Description:
>>> gpio and backlight triggers. In case of the backlight trigger,
>>> it is useful when driving a LED which is intended to indicate
>>> a device in a standby like state.
>>> +
>>> +What: /sys/class/leds/<led>/current-trigger
>>> +Date: September 2019
>>> +KernelVersion: 5.5
>>> +Contact: linux-leds@vger.kernel.org
>>> +Description:
>>> + Set the trigger for this LED. A trigger is a kernel based source
>>> + of LED events.
>>> + Writing the trigger name to this file will change the current
>>> + trigger. Trigger specific parameters can appear in
>>> + /sys/class/leds/<led> once a given trigger is selected. For
>>> + their documentation see sysfs-class-led-trigger-*.
>>> + Reading this file will return the current LED trigger name.
>> Why do we need this new file can't we just update the current trigger
>> file implementation?
> We can't change existing ABI. It doesn't matter if it is documented
> or not - it's in place for very long time and you can't guarantee there
> are no users relying on triggers file show format.
So if it has been in place for a very long time why do we need another
ABI that does sorta the same thing?
This seems to be a bit confusing and extra.
Maybe this ABI should be RO where a user can read the current-trigger as
a single value per file but writing the trigger still
is done through the old ABI.
Dan
>
>> I don't see any documentation that states that the read of the trigger
>> file will print a list of known triggers.
>>
>> And writing to the trigger file still works so I would think the _show
>> just needs to be fixed.
>>
>> Besides this patch does not fix the issue in the commit message that the
>> trigger file still violates the one value per file rule.
>>
>> Dan
>>
>>
next prev parent reply other threads:[~2019-10-02 17:56 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-02 15:12 [PATCH -next 0/2] leds: add substitutes for /sys/class/leds/<led>/trigger Akinobu Mita
2019-10-02 15:13 ` [PATCH -next 1/2] leds: add /sys/devices/virtual/led-trigger/ Akinobu Mita
2019-10-02 15:27 ` Greg Kroah-Hartman
2019-10-02 15:28 ` Greg Kroah-Hartman
2019-10-02 15:13 ` [PATCH -next 2/2] leds: add /sys/class/leds/<led>/current-trigger Akinobu Mita
2019-10-02 15:30 ` Greg Kroah-Hartman
2019-10-02 15:47 ` Dan Murphy
2019-10-02 17:46 ` Jacek Anaszewski
2019-10-02 17:57 ` Dan Murphy [this message]
2019-10-02 18:06 ` Pavel Machek
2019-10-02 18:03 ` [PATCH -next 0/2] leds: add substitutes for /sys/class/leds/<led>/trigger Pavel Machek
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