linux-kernel - Re: [PATCH v5 1/2] dt: bindings: lm3601x: Introduce the lm3601x driver

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Message-ID: <fd68c674-f842-5877-698a-3a74922cb384@gmail.com>
Date:   Thu, 10 May 2018 22:17:24 +0200
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Dan Murphy <dmurphy@...com>, Pavel Machek <pavel@....cz>
Cc:     robh+dt@...nel.org, mark.rutland@....com, afd@...com,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-leds@...r.kernel.org
Subject: Re: [PATCH v5 1/2] dt: bindings: lm3601x: Introduce the lm3601x
 driver

Hi Dan,

On 05/10/2018 09:10 PM, Dan Murphy wrote:
> On 05/10/2018 02:06 PM, Dan Murphy wrote:
>> Pavel
>>
>> On 05/10/2018 01:54 PM, Pavel Machek wrote:
>>> Hi!
>>>
>>>> Introduce the device tree bindings for the lm3601x
>>>> family of LED torch, flash and IR drivers.
>>>>
>>>> Signed-off-by: Dan Murphy <dmurphy@...com>
>>>
>>> Better, thanks.
>>>> +++ b/Documentation/devicetree/bindings/leds/leds-lm3601x.txt
>>>> @@ -0,0 +1,50 @@
>>>> +* Texas Instruments - lm3601x Single-LED Flash Driver
>>>
>>> Ok, so is it single-LED driver, or can it driver ir & white LEDs at
>>> the same time?
>>
>> It is a single LED driver.  It can drive a Torch white LED or IR LED indefinitely or if the driver
>> is programmed to strobe mode the driver will drive the configured LED for the flash timeout specified.
>>
>> Basically a flash and a flash light. IR or White LED.
>>
>>
>>>
>>>> +Example:
>>>> +led-controller@64 {
>>>> +	compatible = "ti,lm36010";
>>>> +	#address-cells = <1>;
>>>> +	#size-cells = <0>;
>>>> +	reg = <0x64>;
>>>> +
>>>> +	led@0 {
>>>> +		reg = <0>;
>>>> +		label = "white:torch";
>>>> +		led-max-microamp = <10000>;
>>>> +	};
>>>> +
>>>> +	led@1 {
>>>> +		reg = <1>;
>>>> +		label = "white:flash";
>>>> +		flash-max-microamp = <10000>;
>>>> +		flash-max-timeout-us = <800>;
>>>> +	};
>>>
>>> Is this realistic config? I'd expect flash to use more power than
>>> torch, and would expect longer timeout than 0.8msec.
>>
>> Timeout in the spreadsheet is ms I will update this example and code
>> Current in the spreadsheet is mA I will update this example and code
>>
>>>
>>> Also.. if this is physically one white LED, it should not be
>>> spread over reg = <0> and reg = <1>...
>>
>> If the torch LED and strobe LED are the same LED how do I expose them both to the user.
>> It is up to consumer to configure the required interfaces they want to expose to the filesystem.

LED flash class interface is prepared for it.
led_clasdev_flash_register() internally calls led_classdev_register(),
so there is brightness file available for torch related operations.

>> Maybe they don't want the strobe feature and just want LED on/off and switch between IR and White.
>>
>> The IR is driven via a different output pin.
> 
> Correction.  There is only one LED drive pin.  The mode selected determines how the device will drive the
> LED.  So you may have one device to drive a Torch and another device to drive the LED.

But only one type of LED can be soldered on the board at a time, right?
If yes, then this is clearly a DT related configuration, and only
one child DT node should be defined for given board.

> Strobe is available in either case but not always required if strobe is not desired by the customer hence
> why I have a separate DT node for it.
> 
> Dan
> 
>>
>> Dan
>>
>>>
>>> Best regards,
>>> 									Pavel
>>>
>>
>>
> 
> 

-- 
Best regards,
Jacek Anaszewski