linux-kernel - Re: [PATCH v2 2/4] leds: add support for TI LP5860 LED driver chip

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Message-ID: <877c0bqisz.fsf@pengutronix.de>
Date: Mon, 14 Jul 2025 10:26:52 +0200
From: Steffen Trumtrar <s.trumtrar@...gutronix.de>
To: Lee Jones <lee@...nel.org>
Cc: Pavel Machek <pavel@....cz>,  Rob Herring <robh@...nel.org>,  Krzysztof
 Kozlowski <krzk+dt@...nel.org>,  Conor Dooley <conor+dt@...nel.org>,
  Steffen Trumtrar <kernel@...gutronix.de>,  Pavel Machek
 <pavel@...nel.org>,  linux-leds@...r.kernel.org,
  devicetree@...r.kernel.org,  linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/4] leds: add support for TI LP5860 LED driver chip


Hi,

On 2025-05-23 at 11:28 +01, Lee Jones <lee@...nel.org> wrote:

> On Wed, 14 May 2025, Steffen Trumtrar wrote:
> 
> > Add support for the Texas Instruments LP5860 LED driver chip
> > via SPI interfaces.
> > 
> > The LP5860 is an LED matrix driver for up to 196 LEDs, which supports
> > short and open detection of the individual channel select lines.
> > 
> > The original driver is from an unknown author at Texas Instruments. Only
> > the cryptic handle 'zlzx' is known.
> > 
> > Co-developed-by: Steffen Trumtrar <s.trumtrar@...gutronix.de>
> > Signed-off-by: Steffen Trumtrar <s.trumtrar@...gutronix.de>
> > ---
> >  Documentation/ABI/testing/sysfs-class-spi-lp5860 |  23 ++
> >  drivers/leds/Kconfig                             |  23 ++
> >  drivers/leds/Makefile                            |   2 +
> >  drivers/leds/leds-lp5860-core.c                  | 276 ++++++++++++++++++++
> >  drivers/leds/leds-lp5860-spi.c                   |  99 +++++++
> 
> Are you going to follow-up with another option?  Say I2C?

the chip also supports connection via I2C, but it's unlikely that I will add that myself.

> >  drivers/leds/leds-lp5860.h                       | 315 +++++++++++++++++++++++
> >  6 files changed, 738 insertions(+)
> > 
> > diff --git a/Documentation/ABI/testing/sysfs-class-spi-lp5860 b/Documentation/ABI/testing/sysfs-class-spi-lp5860
> 
> This doesn't belong here.
> 
> > new file mode 100644
> > index 0000000000000000000000000000000000000000..d24b49d38ecae55f1a1a4e465fbe71d30eff497e
> > --- /dev/null
> > +++ b/Documentation/ABI/testing/sysfs-class-spi-lp5860
> > @@ -0,0 +1,23 @@
> > +What:           /sys/class/spi_master/spi<bus>/spi<bus>.<dev>/b_current_set
> 
> Why would you want to change the current of the SPI bus?
>

Where does it belong? I grepped and followed the eeprom (Documentation/ABI/testing/sysfs-class-spi-eeprom) which uses sernum in the same way. Directions welcome.

> 
> > +Date:           May 2025
> > +KernelVersion:  6.15
> > +Contact:        Steffen Trumtrar <kernel@...gutronix.de>
> > +Description:
> > +	Contains and sets the current for the B color group.
> 
> What does the current set?  Brightness?
> 
> If so, the user shouldn't be expected to know what current set in order
> to obtain a specific brightness.  Instead, shouldn't you use
> /sys/class/leds/<led>/multi_intensity and let the driver deal with the
> particulars of setting that brightness?
>

The chip has a global setting for the current of the three color groups. And an indiviual setting for every LED itself. The multi_intensity is for one LED as far as I understand. And the brightness of the whole matrix can be controlled via this global current setting.


(...)

Thanks for the rest of the feedback. I already addressed all of that in my patches, but I'm not sure what is the correct way to proceed with the sysfs ABI entries.


Thanks,
Steffen

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