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From: Jean-Jacques Hiblot <jjhiblot@ti.com>
To: Pavel Machek <pavel@ucw.cz>
Cc: mark.rutland@arm.com,
	Daniel Thompson <daniel.thompson@linaro.org>,
	jingoohan1@gmail.com, tomi.valkeinen@ti.com,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	robh+dt@kernel.org, jacek.anaszewski@gmail.com,
	lee.jones@linaro.org, linux-leds@vger.kernel.org, dmurphy@ti.com
Subject: Re: [PATCH 3/4] backlight: add led-backlight driver
Date: Fri, 5 Jul 2019 12:33:33 +0200	[thread overview]
Message-ID: <6c21af33-8c3b-58a8-0a1b-f85fb9f80050@ti.com> (raw)
In-Reply-To: <20190705100851.zn2jkipj4fxq5we6@devuan>

Pavel

On 05/07/2019 12:08, Pavel Machek wrote:
> Hi!
>
>>>>> Also still relevant is whether the LED device is being correctly
>>>>> modelled if the act of turning on the LED doesn't, in fact, turn the LED
>>>>> on. Is it *really* a correct implementation of an LED device that
>>>>> setting it to LED_FULL using sysfs doesn't cause it to light up?
>>>> What I understood from the discussion between Rob and Tomi is that the
>>>> child-node of the LED controller should be considered a backlight device,
>>>> not a simple LED. I'm not sure if the sysfs interface is still relevant in
>>>> that case. Maybe it should just be disabled by the backlight driver
>>>> (possible with led_sysfs_disable())
>>> led_sysfs_disable() sounds like a sensible change but that's not quite
>>> what I mean.
>>>
>>> It is more a thought experiment to see if the power control *should* be
>>> implemented by the backlight. Consider what happens if we *don't*
>>> enable CONFIG_BACKLIGHT_LED in the kernel: we would still have an LED
>>> device and it would not work correctly.
>>>
>>> In other words I naively expect turning on an LED using the LED API
>>> (any of them, sysfs or kernel) to result in the LED turning on.
>>> Implementing a workaround in the client for what appears to be
>>> something missing in the LED driver strikes me as odd. Why shouldn't
>>> the regulator be managed in the LED driver?
>> I see your point. Indeed having the regulator handled in the LED-core makes
>> sense in a lot of situations
>>
>> I'll think about it.
> For the record, I also believe regulator and enable gpio should be
> handled in the core.

I am working on adding the regulator to the led core.

I don't really want to add a GPIO enable to the core though. If needed 
it can be described as a GPIO-enabled regulator up(/down)stream the 
regular regulator.

JJ


>
> 									Pavel
> PS please trim down the quoted text.									
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WARNING: multiple messages have this Message-ID (diff)
From: Jean-Jacques Hiblot <jjhiblot@ti.com>
To: Pavel Machek <pavel@ucw.cz>
Cc: Daniel Thompson <daniel.thompson@linaro.org>,
	<jacek.anaszewski@gmail.com>, <robh+dt@kernel.org>,
	<mark.rutland@arm.com>, <lee.jones@linaro.org>,
	<jingoohan1@gmail.com>, <dmurphy@ti.com>,
	<linux-leds@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<dri-devel@lists.freedesktop.org>, <tomi.valkeinen@ti.com>
Subject: Re: [PATCH 3/4] backlight: add led-backlight driver
Date: Fri, 5 Jul 2019 12:33:33 +0200	[thread overview]
Message-ID: <6c21af33-8c3b-58a8-0a1b-f85fb9f80050@ti.com> (raw)
Message-ID: <20190705103333.r1GDsOwRttBnf_7ka0oy0l5QtUXEeKwfQ9RCD0lU4-M@z> (raw)
In-Reply-To: <20190705100851.zn2jkipj4fxq5we6@devuan>

Pavel

On 05/07/2019 12:08, Pavel Machek wrote:
> Hi!
>
>>>>> Also still relevant is whether the LED device is being correctly
>>>>> modelled if the act of turning on the LED doesn't, in fact, turn the LED
>>>>> on. Is it *really* a correct implementation of an LED device that
>>>>> setting it to LED_FULL using sysfs doesn't cause it to light up?
>>>> What I understood from the discussion between Rob and Tomi is that the
>>>> child-node of the LED controller should be considered a backlight device,
>>>> not a simple LED. I'm not sure if the sysfs interface is still relevant in
>>>> that case. Maybe it should just be disabled by the backlight driver
>>>> (possible with led_sysfs_disable())
>>> led_sysfs_disable() sounds like a sensible change but that's not quite
>>> what I mean.
>>>
>>> It is more a thought experiment to see if the power control *should* be
>>> implemented by the backlight. Consider what happens if we *don't*
>>> enable CONFIG_BACKLIGHT_LED in the kernel: we would still have an LED
>>> device and it would not work correctly.
>>>
>>> In other words I naively expect turning on an LED using the LED API
>>> (any of them, sysfs or kernel) to result in the LED turning on.
>>> Implementing a workaround in the client for what appears to be
>>> something missing in the LED driver strikes me as odd. Why shouldn't
>>> the regulator be managed in the LED driver?
>> I see your point. Indeed having the regulator handled in the LED-core makes
>> sense in a lot of situations
>>
>> I'll think about it.
> For the record, I also believe regulator and enable gpio should be
> handled in the core.

I am working on adding the regulator to the led core.

I don't really want to add a GPIO enable to the core though. If needed 
it can be described as a GPIO-enabled regulator up(/down)stream the 
regular regulator.

JJ


>
> 									Pavel
> PS please trim down the quoted text.									

  parent reply	other threads:[~2019-07-05 10:33 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-01 15:14 [PATCH 0/4] Add a generic driver for LED-based backlight Jean-Jacques Hiblot
2019-07-01 15:14 ` [PATCH 1/4] leds: of: create a child device if the LED node contains a "compatible" string Jean-Jacques Hiblot
2019-07-01 15:14 ` [PATCH 2/4] devicetree: Update led binding Jean-Jacques Hiblot
2019-07-01 15:20   ` Dan Murphy
2019-07-01 15:14 ` [PATCH 3/4] backlight: add led-backlight driver Jean-Jacques Hiblot
2019-07-02  9:54   ` Daniel Thompson
2019-07-02 10:59     ` Jean-Jacques Hiblot
2019-07-02 13:04       ` Daniel Thompson
2019-07-02 15:17         ` Jean-Jacques Hiblot
2019-07-03  9:44           ` Daniel Thompson
2019-07-03 10:02             ` Jean-Jacques Hiblot
2019-07-05 10:08               ` Pavel Machek
2019-07-05 10:08                 ` Pavel Machek
2019-07-05 10:33                 ` Jean-Jacques Hiblot [this message]
2019-07-05 10:33                   ` Jean-Jacques Hiblot
2019-07-01 15:14 ` [PATCH 4/4] devicetree: Add led-backlight binding Jean-Jacques Hiblot
2019-07-02  9:58   ` Daniel Thompson
2019-07-02 11:11     ` Jean-Jacques Hiblot
2019-07-05 10:11   ` Pavel Machek
2019-07-05 10:11     ` Pavel Machek
2019-07-05 10:14 ` [PATCH 0/4] Add a generic driver for LED-based backlight Pavel Machek
2019-07-05 10:14   ` Pavel Machek
2019-07-05 10:29   ` Daniel Thompson
2019-07-05 10:29     ` Daniel Thompson
2019-07-05 11:34   ` Jean-Jacques Hiblot
2019-07-05 11:34     ` Jean-Jacques Hiblot
2019-07-05 23:23   ` Sebastian Reichel
2019-07-05 23:23     ` Sebastian Reichel

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