Re: [PATCH v8 0/5] auxdisplay: add support for TI LP5812 4x3 Matrix LED driver

[Andy Shevchenko <andy@kernel.org>]

On Sat, May 10, 2025 at 02:48:02PM +0700, Nam Tran wrote:
> On Thu, 8 May 2025 Lee Jones wrote:
> > On Thu, 08 May 2025, Andy Shevchenko wrote:
> > > On Thu, May 8, 2025 at 5:27 PM Nam Tran <trannamatk@gmail.com> wrote:
> > > > On Thu, 8 May 2025 Lee Jones wrote:
> > > > > On Thu, 08 May 2025, Andy Shevchenko wrote:
> > > > > > On Wed, May 7, 2025 at 7:42 PM Nam Tran <trannamatk@gmail.com> wrote:

...

> > > > > > At least, based on the above it's my formal NAK from an auxdisplay perspective.
> > > > >
> > > > > This is fine.
> > > > >
> > > > > Just be aware, before you submit to LEDs again, that you need to use
> > > > > what is available in the LEDs subsystem to it's fullest, before
> > > > > hand-rolling all of your own APIs.  The first submission didn't use a
> > > > > single LED API.  This, as before, would be a big NACK also.
> > > >
> > > > Thanks for the clarification.
> > > >
> > > > Just to confirm — the current version of the driver is customized to allow
> > > > user space to directly manipulate LP5812 registers and to support the
> > > > device’s full feature set. Because of this, it doesn’t follow the standard
> > > > LED interfaces.
> > > 
> > > But why? What's wrong with the LED ABI? (see also below question
> > > before answering to this one)
> > > 
> > > > Given that, would it be acceptable to submit this driver under the misc subsystem instead?
> > > 
> > > But these are LEDs in the hardware and you can access them as 4
> > > individual LEDs, right?
> > 
> > Right.  Please work with the API you are offered in the first instance.
> > My first assumption is always that this driver isn't as special as you
> > think it might be.
> 
> In direct mode, we can access them as individual LEDS. User doesn't need
> to select LEDs. In this mode, it is a simple LED driver.
> 
> However, user must select LEDs in scan mode. The hardware uses 4 pin to
> display 12 LEDs (or 4 RGB LEDs). Ordering of LED selection also impact
> to display capacibility. That why, I need to support another interface
> for user to controll hardware's registers.
> 
> In mix mode, we can control an individual LED and up to 6 scan LEDs.
> However, user must select the order of single LED and which LEDs will be
> use for scan function.
> 
> The main point is user must have capacibility in write information to
> hardware's registers to select LEDs in scan mode and mix mode.
>  
> Besides system modes (direct mode, scan mode, mix mode), each LED has
> manual mode and autonomous mode.
>  
> A example steps to display a LED in manual mode
> # Set drive mode is Scan mode with 4 scan. Scan order 0 is out_0,
> # Scan order 1 is out_1, Scan order 2 is out_2, and Scan order 3 is out_3
> echo tcmscan:4:0:1:2:3 > /sys/bus/i2c/drivers/lp5812/1-001b/lp5812_chip_setup/dev_config
> # Enable led_A0
> echo 1 > /sys/bus/i2c/drivers/lp5812/1-001b/led_A0/activate
> # Enable manual mode
> echo manual > /sys/bus/i2c/drivers/lp5812/1-001b/led_A0/mode
> # Set Dot Current
> echo 100 > /sys/bus/i2c/drivers/lp5812/1-001b/led_A0/manual_dc
> # Set Manual PWM
> echo 100 > /sys/bus/i2c/drivers/lp5812/1-001b/led_A0/manual_pwm
>  
> However in autonomous mode, the steps are complicated
> # Set drive mode is Scan mode with 4 scan. Scan order 0 is out_0,
> # Scan order 1 is out_1, Scan order 2 is out_2, and Scan order 3 is out_3
> echo tcmscan:4:0:1:2:3 > /sys/bus/i2c/drivers/lp5812/1-001b/lp5812_chip_setup/dev_config
> # Enable led_A0
> echo 1 > /sys/bus/i2c/drivers/lp5812/1-001b/led_A0/activate
> # Enable autonomous mode
> echo autonomous > /sys/bus/i2c/drivers/lp5812/1-001b/led_A0/mode
> # Config autonomous animation mode: (only use AEU1, start pause time: 3.04s,
> # stop pause time: 3.04s, playback time: infinite time)
> echo 1:10:10:15 > /sys/bus/i2c/drivers/lp5812/1-001b/led_A0/mode
> # Config AEU1 playback times
> echo 1 > /sys/bus/i2c/drivers/lp5812/1-001b/led_A0/AEU1/playback_time
> # Config PWM
> echo 100 > /sys/bus/i2c/drivers/lp5812/1-001b/led_A0/AEU1/pwm1
> echo 100 > /sys/bus/i2c/drivers/lp5812/1-001b/led_A0/AEU1/pwm2
> echo 100 > /sys/bus/i2c/drivers/lp5812/1-001b/led_A0/AEU1/pwm3
> echo 100 > /sys/bus/i2c/drivers/lp5812/1-001b/led_A0/AEU1/pwm4
> echo 100 > /sys/bus/i2c/drivers/lp5812/1-001b/led_A0/AEU1/pwm5
> # Config slope time
> echo 5 > /sys/bus/i2c/drivers/lp5812/1-001b/led_A0/AEU1/slope_time_t1
> echo 5 > /sys/bus/i2c/drivers/lp5812/1-001b/led_A0/AEU1/slope_time_t2
> echo 5 > /sys/bus/i2c/drivers/lp5812/1-001b/led_A0/AEU1/slope_time_t3
> echo 5 > /sys/bus/i2c/drivers/lp5812/1-001b/led_A0/AEU1/slope_time_t4
> # Start autonomous
> echo start > /sys/bus/i2c/drivers/lp5812/1-001b/lp5812_chip_setup/device_command
>  
> I think setting PWM also same as brightness_set API. However, there are
> many PWM config for a LED and it is one of other config to make autonomous mode work.
> Therefore, standard led API can use in some use cases only.
> 
> Please see the link below for a better visualization of how to configure the LP5812.
> https://dev.ti.com/gallery/view/LED/LP581x/ver/0.10.0/

To me it sounds like you should start from the small steps, i.e. do not
implement everything at once. And starting point of the 4 RGB LEDs sounds
the best approach to me. Then, if needed, you can always move on with
fancy features of this hardware on top of the existing code.

-- 
With Best Regards,
Andy Shevchenko