Re: [PATCH v1] leds: Clarify supported chips by LM355x driver

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Mon, 2018-01-29 at 21:46 +0100, Jacek Anaszewski wrote:
> On 01/28/2018 03:30 PM, Andy Shevchenko wrote:
> > On Fri, 2018-01-26 at 21:39 +0100, Jacek Anaszewski wrote:
> > > On 01/26/2018 08:38 AM, Andy Shevchenko wrote:
> > > > +	  Note, LM3555 is driven by AS3645A.
> > > 
> > > Could you please provide more details on this relationship?
> > > Looking at the datasheet it seems that both chips are standalone
> > > and controlled via I2C and/or via GPIO in case of LM3555.
> > 
> > The only difference I see looking in datasheets again that AS3645A
> > supports dual-led mode, by using STROBE signal in case of parallel
> > interface or thru additional bits in I2C mode.
> > 
> > Can you be more specific what exactly makes you feel that they are
> > not
> > compatible?
> 
> The expression "LM3555 is driven by AS3645A" brings on mind rather
> some type of hardware dependency between chips than drivers
> similarity.
> 
> Now I understand that you meant that both devices can be driven by any
> of leds-lm355x or leds-as3645a driver, am I right?

No. The chip in question is LM3555, and it's handled only in as3645a
driver.

> I suspected that I got something entirely wrong here, especially
> that both you and Pavel agreed.
> 
> But, given that it turned out that leds-lm355x.c doesn't support
> LM3555 and its documentation [3] indeed shows the affinity with
> AS3645, I suppose that this patch is a result of a premature
> conclusion drawn basing on the driver's description rather than its
> capabilities.
> 
> [3] http://www.ti.com/lit/ds/symlink/lm3555.pdf
> 
> Effectively, the only sensible change seems to be:
> 
> -	tristate "LED support for LM355x Chips, LM3554 and LM3556"
> +	tristate "LED support for LM3554 and LM3556 chips"
>  	depends on LEDS_CLASS && I2C
>  	select REGMAP_I2C
>  	help
> -	  This option enables support for LEDs connected to LM355x.
> -	  LM355x includes Torch, Flash and Indicator functions.
> +	  This option enables support for LEDs connected to LM3554
> +	  and LM3556. It includes Torch, Flash and Indicator
> functions.

I like patch Pavel sent previously. It feels more comprehensive than
this one.

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy