Re: [PATCH 3/4] leds: Add driver for the ISSI IS31FL32xx family of LED controllers

Jacek Anaszewski
2016-03-04T21:39:35Z

On 03/04/2016 08:02 PM, David Rivshin (Allworx) wrote:
> On Fri, 04 Mar 2016 17:01:52 +0100
> Jacek Anaszewski <j.anaszewski@samsung.com> wrote:
>
>> On 03/04/2016 04:05 PM, David Rivshin (Allworx) wrote:
>>> On Fri, 04 Mar 2016 08:54:02 +0100
>>> Jacek Anaszewski <j.anaszewski@samsung.com> wrote:
>>>
>>>> On 03/04/2016 01:45 AM, David Rivshin (Allworx) wrote:
>>>>> On Thu, 03 Mar 2016 15:51:32 +0100
>>>>> Jacek Anaszewski <j.anaszewski@samsung.com> wrote:
>>>>>
>>>>>> Hi David,
>>>>>>
>>>>>> Thanks for the update. Two remarks in the code.
>>>>>>
>>>>>> On 03/03/2016 04:01 AM, David Rivshin (Allworx) wrote:
>>>>>>> From: David Rivshin <drivshin@allworx.com>
>>>>>>>
>>>>>>> The IS31FL32xx family of LED controllers are I2C devices with multiple
>>>>>>> constant-current channels, each with independent 256-level PWM control.
>>>>>>>
>>>>>>> Datasheets: http://www.issi.com/US/product-analog-fxled-driver.shtml
>>>>>>>
>>>>>>> This has been tested on the IS31FL3236 and IS31FL3216, on an ARM
>>>>>>> (TI am335x) platform.
>>>>>>>
>>>>>>> The programming paradigm of these devices is similar in the following
>>>>>>> ways:
>>>>>>> - All registers are 8 bit
>>>>>>> - All LED control registers are write-only
>>>>>>> - Each LED channel has a PWM register (0-255)
>>>>>>> - PWM register writes are shadowed until an Update register is poked
>>>>>>> - All have a concept of Software Shutdown, which disables output
>>>>>>>
>>>>>>> However, there are some differences in devices:
>>>>>>> - 3236/3235 have a separate Control register for each LED,
>>>>>>> (3218/3216 pack the enable bits into fewer registers)
>>>>>>> - 3236/3235 have a per-channel current divisor setting
>>>>>>> - 3236/3235 have a Global Control register that can turn off all LEDs
>>>>>>> - 3216 is unique in a number of ways
>>>>>>> - OUT9-OUT16 can be configured as GPIOs instead of LED controls
>>>>>>> - LEDs can be programmed with an 8-frame animation, with
>>>>>>> programmable delay between frames
>>>>>>> - LEDs can be modulated by an input audio signal
>>>>>>> - Max output current can be adjusted from 1/4 to 2x globally
>>>>>>> - Has a Configuration register instead of a Shutdown register
>>>>>>>
>>>>>>> This driver currently only supports the base PWM control function
>>>>>>> of these devices. The following features of these devices are not
>>>>>>> implemented, although it should be possible to add them in the future:
>>>>>>> - All devices are capable of going into a lower-power "software
>>>>>>> shutdown" mode.
>>>>>>> - The is31fl3236 and is31fl3235 can reduce the max output current
>>>>>>> per-channel with a divisor of 1, 2, 3, or 4.
>>>>>>> - The is31fl3216 can use some LED channels as GPIOs instead.
>>>>>>> - The is31fl3216 can animate LEDs in hardware.
>>>>>>> - The is31fl3216 can modulate LEDs according to an audio input.
>>>>>>> - The is31fl3216 can reduce/increase max output current globally.
>>>>>>>
>>>>>>> Signed-off-by: David Rivshin <drivshin@allworx.com>
>>>>>>> ---
>>>>>>>
>>>>>>> You may see two instances of this warning:
>>>>>>> "passing argument 1 of 'of_property_read_string' discards 'const'
>>>>>>> qualifier from pointer target type"
>>>>>>> That is a result of of_property_read_string() taking a non-const
>>>>>>> struct device_node pointer parameter. I have separately submitted a
>>>>>>> patch to fix that [1], and a few related functions which had the same
>>>>>>> issue. I'm hoping that will get into linux-next before this does, so
>>>>>>> that the warnings never show up there.
>>>>>>
>>>>>> Please adjust the patch so that it compiles without warnings on
>>>>>> current linux-next. Your patch for DT API hasn't been reviewed yet
>>>>>> AFICS, and I can imagine that there will be some resistance against.
>>>>>
>>>>> Since the DT API patch was just accepted by Rob [1], would it be OK
>>>>> to wait for the results of Stefan's testing (and any other reviews)
>>>>> before making a decision on this? From Stefan's note, it won't be
>>>>> until this weekend that he will have a chance to test, and I'm
>>>>> guessing the DT API patch will make its way through Rob's tree to
>>>>> linux-next by then.
>>>>
>>>> OK.
>>>>
>>>>> FYI, the warning workaround would be to make the second parameter to
>>>>> is31fl32xx_parse_child_dt() non-const.
>>>>>
>>>>> [1] https://lkml.org/lkml/2016/3/3/924
>>>>>
>>>>>>> Changes from RFC:
>>>>>>> - Removed max-brightness DT property.
>>>>>>> - Refer to these devices as "LED controllers" in Kconfig.
>>>>>>> - Removed redundant last sentence from Kconfig entry
>>>>>>> - Removed unnecessary debug code.
>>>>>>> - Do not set led_classdev.brightness to 0 explicitly, as it is
>>>>>>> already initialized to 0 by devm_kzalloc().
>>>>>>> - Used of_property_read_string() instead of of_get_property().
>>>>>>> - Fail immediately on DT parsing error in a child node, rather than
>>>>>>> continuing on with the non-faulty ones.
>>>>>>> - Added additional comments for some things that might be non-obvious.
>>>>>>> - Added constants for the location of the SSD bit in the SHUTDOWN
>>>>>>> register, and the 3216's CONFIG register.
>>>>>>> - Added special sw_shutdown_func for the 3216 device, as that bit
>>>>>>> is in a different register, at a different position, and has reverse
>>>>>>> polarity compared to all the other devices.
>>>>>>> - Refactored is31fl32xx_init_regs() to separate out some logic into
>>>>>>> is31fl32xx_reset_regs() and is31fl32xx_software_shutdown().
>>>>>>>
>>>>>>> [1] https://lkml.org/lkml/2016/3/2/746
>>>>>>>
>>>>>>> drivers/leds/Kconfig | 8 +
>>>>>>> drivers/leds/Makefile | 1 +
>>>>>>> drivers/leds/leds-is31fl32xx.c | 505 +++++++++++++++++++++++++++++++++++++++++
>>>>>>> 3 files changed, 514 insertions(+)
>>>>>>> create mode 100644 drivers/leds/leds-is31fl32xx.c
>>>>>>>
>>>>>>> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
>>>>>>> index 1034696..9c63ba4 100644
>>>>>>> --- a/drivers/leds/Kconfig
>>>>>>> +++ b/drivers/leds/Kconfig
>>>>>>> @@ -580,6 +580,14 @@ config LEDS_SN3218
>>>>>>> This driver can also be built as a module. If so the module
>>>>>>> will be called leds-sn3218.
>>>>>>>
>>>>>>> +config LEDS_IS31FL32XX
>>>>>>> + tristate "LED support for ISSI IS31FL32XX I2C LED controller family"
>>>>>>> + depends on LEDS_CLASS && I2C && OF
>>>>>>> + help
>>>>>>> + Say Y here to include support for ISSI IS31FL32XX LED controllers.
>>>>>>> + They are I2C devices with multiple constant-current channels, each
>>>>>>> + with independent 256-level PWM control.
>>>>>>> +
>>>>>>> comment "LED driver for blink(1) USB RGB LED is under Special HID drivers (HID_THINGM)"
>>>>>>>
>>>>>>> config LEDS_BLINKM
>>>>>>> diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
>>>>>>> index 89c9b6f..3fdf313 100644
>>>>>>> --- a/drivers/leds/Makefile
>>>>>>> +++ b/drivers/leds/Makefile
>>>>>>> @@ -67,6 +67,7 @@ obj-$(CONFIG_LEDS_KTD2692) += leds-ktd2692.o
>>>>>>> obj-$(CONFIG_LEDS_POWERNV) += leds-powernv.o
>>>>>>> obj-$(CONFIG_LEDS_SEAD3) += leds-sead3.o
>>>>>>> obj-$(CONFIG_LEDS_SN3218) += leds-sn3218.o
>>>>>>> +obj-$(CONFIG_LEDS_IS31FL32XX) += leds-is31fl32xx.o
>>>>>>>
>>>>>>> # LED SPI Drivers
>>>>>>> obj-$(CONFIG_LEDS_DAC124S085) += leds-dac124s085.o
>>>>>>> diff --git a/drivers/leds/leds-is31fl32xx.c b/drivers/leds/leds-is31fl32xx.c
>>>>>>> new file mode 100644
>>>>>>> index 0000000..49818f0
>>>>>>> --- /dev/null
>>>>>>> +++ b/drivers/leds/leds-is31fl32xx.c
>>>>>>> @@ -0,0 +1,505 @@
>>>>>>> +/*
>>>>>>> + * linux/drivers/leds-is31fl32xx.c
>>>>>>> + *
>>>>>>> + * Driver for ISSI IS31FL32xx family of I2C LED controllers
>>>>>>> + *
>>>>>>> + * Copyright 2015 Allworx Corp.
>>>>>>> + *
>>>>>>> + *
>>>>>>> + * This program is free software; you can redistribute it and/or modify
>>>>>>> + * it under the terms of the GNU General Public License version 2 as
>>>>>>> + * published by the Free Software Foundation.
>>>>>>> + *
>>>>>>> + * Datasheets: http://www.issi.com/US/product-analog-fxled-driver.shtml
>>>>>>> + */
>>>>>>> +
>>>>>>> +#include <linux/err.h>
>>>>>>> +#include <linux/i2c.h>
>>>>>>> +#include <linux/kernel.h>
>>>>>>> +#include <linux/leds.h>
>>>>>>> +#include <linux/module.h>
>>>>>>> +#include <linux/of_platform.h>
>>>>>>> +
>>>>>>> +/* Used to indicate a device has no such register */
>>>>>>> +#define IS31FL32XX_REG_NONE 0xFF
>>>>>>> +
>>>>>>> +/* Software Shutdown bit in Shutdown Register */
>>>>>>> +#define IS31FL32XX_SHUTDOWN_SSD_ENABLE 0
>>>>>>> +#define IS31FL32XX_SHUTDOWN_SSD_DISABLE BIT(0)
>>>>>>> +
>>>>>>> +/* IS31FL3216 has a number of unique registers */
>>>>>>> +#define IS31FL3216_CONFIG_REG 0x00
>>>>>>> +#define IS31FL3216_LIGHTING_EFFECT_REG 0x03
>>>>>>> +#define IS31FL3216_CHANNEL_CONFIG_REG 0x04
>>>>>>> +
>>>>>>> +/* Software Shutdown bit in 3216 Config Register */
>>>>>>> +#define IS31FL3216_CONFIG_SSD_ENABLE BIT(7)
>>>>>>> +#define IS31FL3216_CONFIG_SSD_DISABLE 0
>>>>>>> +
>>>>>>> +struct is31fl32xx_priv;
>>>>>>> +struct is31fl32xx_led_data {
>>>>>>> + struct led_classdev cdev;
>>>>>>> + u8 channel; /* 1-based, max priv->cdef->channels */
>>>>>>> + struct is31fl32xx_priv *priv;
>>>>>>> +};
>>>>>>> +
>>>>>>> +struct is31fl32xx_priv {
>>>>>>> + const struct is31fl32xx_chipdef *cdef;
>>>>>>> + struct i2c_client *client;
>>>>>>> + unsigned int num_leds;
>>>>>>> + struct is31fl32xx_led_data leds[0];
>>>>>>> +};
>>>>>>> +
>>>>>>> +/**
>>>>>>> + * struct is31fl32xx_chipdef - chip-specific attributes
>>>>>>> + * @channels : Number of LED channels
>>>>>>> + * @shutdown_reg : address of Shutdown register (optional)
>>>>>>> + * @pwm_update_reg : address of PWM Update register
>>>>>>> + * @global_control_reg : address of Global Control register (optional)
>>>>>>> + * @reset_reg : address of Reset register (optional)
>>>>>>> + * @pwm_register_base : address of first PWM register
>>>>>>> + * @pwm_registers_reversed: : true if PWM registers count down instead of up
>>>>>>> + * @led_control_register_base : address of first LED control register (optional)
>>>>>>> + * @enable_bits_per_led_control_register: number of LEDs enable bits in each
>>>>>>> + * @reset_func: : pointer to reset function
>>>>>>> + *
>>>>>>> + * For all optional register addresses, the sentinel value %IS31FL32XX_REG_NONE
>>>>>>> + * indicates that this chip has no such register.
>>>>>>> + *
>>>>>>> + * If non-NULL, @reset_func will be called during probing to set all
>>>>>>> + * necessary registers to a known initialization state. This is needed
>>>>>>> + * for chips that do not have a @reset_reg.
>>>>>>> + *
>>>>>>> + * @enable_bits_per_led_control_register must be >=1 if
>>>>>>> + * @led_control_register_base != %IS31FL32XX_REG_NONE.
>>>>>>> + */
>>>>>>> +struct is31fl32xx_chipdef {
>>>>>>> + u8 channels;
>>>>>>> + u8 shutdown_reg;
>>>>>>> + u8 pwm_update_reg;
>>>>>>> + u8 global_control_reg;
>>>>>>> + u8 reset_reg;
>>>>>>> + u8 pwm_register_base;
>>>>>>> + bool pwm_registers_reversed;
>>>>>>> + u8 led_control_register_base;
>>>>>>> + u8 enable_bits_per_led_control_register;
>>>>>>> + int (*reset_func)(struct is31fl32xx_priv *priv);
>>>>>>> + int (*sw_shutdown_func)(struct is31fl32xx_priv *priv, bool enable);
>>>>>>> +};
>>>>>>> +
>>>>>>> +static const struct is31fl32xx_chipdef is31fl3236_cdef = {
>>>>>>> + .channels = 36,
>>>>>>> + .shutdown_reg = 0x00,
>>>>>>> + .pwm_update_reg = 0x25,
>>>>>>> + .global_control_reg = 0x4a,
>>>>>>> + .reset_reg = 0x4f,
>>>>>>> + .pwm_register_base = 0x01,
>>>>>>> + .led_control_register_base = 0x26,
>>>>>>> + .enable_bits_per_led_control_register = 1,
>>>>>>> +};
>>>>>>> +
>>>>>>> +static const struct is31fl32xx_chipdef is31fl3235_cdef = {
>>>>>>> + .channels = 28,
>>>>>>> + .shutdown_reg = 0x00,
>>>>>>> + .pwm_update_reg = 0x25,
>>>>>>> + .global_control_reg = 0x4a,
>>>>>>> + .reset_reg = 0x4f,
>>>>>>> + .pwm_register_base = 0x05,
>>>>>>> + .led_control_register_base = 0x2a,
>>>>>>> + .enable_bits_per_led_control_register = 1,
>>>>>>> +};
>>>>>>> +
>>>>>>> +static const struct is31fl32xx_chipdef is31fl3218_cdef = {
>>>>>>> + .channels = 18,
>>>>>>> + .shutdown_reg = 0x00,
>>>>>>> + .pwm_update_reg = 0x16,
>>>>>>> + .global_control_reg = IS31FL32XX_REG_NONE,
>>>>>>> + .reset_reg = 0x17,
>>>>>>> + .pwm_register_base = 0x01,
>>>>>>> + .led_control_register_base = 0x13,
>>>>>>> + .enable_bits_per_led_control_register = 6,
>>>>>>> +};
>>>>>>> +
>>>>>>> +static int is31fl3216_reset(struct is31fl32xx_priv *priv);
>>>>>>> +static int is31fl3216_software_shutdown(struct is31fl32xx_priv *priv,
>>>>>>> + bool enable);
>>>>>>> +static const struct is31fl32xx_chipdef is31fl3216_cdef = {
>>>>>>> + .channels = 16,
>>>>>>> + .shutdown_reg = IS31FL32XX_REG_NONE,
>>>>>>> + .pwm_update_reg = 0xB0,
>>>>>>> + .global_control_reg = IS31FL32XX_REG_NONE,
>>>>>>> + .reset_reg = IS31FL32XX_REG_NONE,
>>>>>>> + .pwm_register_base = 0x10,
>>>>>>> + .pwm_registers_reversed = true,
>>>>>>> + .led_control_register_base = 0x01,
>>>>>>> + .enable_bits_per_led_control_register = 8,
>>>>>>> + .reset_func = is31fl3216_reset,
>>>>>>> + .sw_shutdown_func = is31fl3216_software_shutdown,
>>>>>>> +};
>>>>>>> +
>>>>>>> +static int is31fl32xx_write(struct is31fl32xx_priv *priv, u8 reg, u8 val)
>>>>>>> +{
>>>>>>> + int ret;
>>>>>>> +
>>>>>>> + dev_dbg(&priv->client->dev, "writing register 0x%02X=0x%02X", reg, val);
>>>>>>> +
>>>>>>> + ret = i2c_smbus_write_byte_data(priv->client, reg, val);
>>>>>>> + if (ret) {
>>>>>>> + dev_err(&priv->client->dev,
>>>>>>> + "register write to 0x%02X failed (error %d)",
>>>>>>> + reg, ret);
>>>>>>> + }
>>>>>>> + return ret;
>>>>>>> +}
>>>>>>> +
>>>>>>> +/*
>>>>>>> + * Custom reset function for IS31FL3216 because it does not have a RESET
>>>>>>> + * register the way that the other IS31FL32xx chips do. We don't bother
>>>>>>> + * writing the GPIO and animation registers, because the registers we
>>>>>>> + * do write ensure those will have no effect.
>>>>>>> + */
>>>>>>> +static int is31fl3216_reset(struct is31fl32xx_priv *priv)
>>>>>>> +{
>>>>>>> + unsigned int i;
>>>>>>> + int ret;
>>>>>>> +
>>>>>>> + ret = is31fl32xx_write(priv, IS31FL3216_CONFIG_REG,
>>>>>>> + IS31FL3216_CONFIG_SSD_ENABLE);
>>>>>>> + if (ret)
>>>>>>> + return ret;
>>>>>>> + for (i = 0; i < priv->cdef->channels; i++) {
>>>>>>> + ret = is31fl32xx_write(priv, priv->cdef->pwm_register_base+i,
>>>>>>> + 0x00);
>>>>>>> + if (ret)
>>>>>>> + return ret;
>>>>>>> + }
>>>>>>> + ret = is31fl32xx_write(priv, priv->cdef->pwm_update_reg, 0);
>>>>>>> + if (ret)
>>>>>>> + return ret;
>>>>>>> + ret = is31fl32xx_write(priv, IS31FL3216_LIGHTING_EFFECT_REG, 0x00);
>>>>>>> + if (ret)
>>>>>>> + return ret;
>>>>>>> + ret = is31fl32xx_write(priv, IS31FL3216_CHANNEL_CONFIG_REG, 0x00);
>>>>>>> + if (ret)
>>>>>>> + return ret;
>>>>>>> +
>>>>>>> + return 0;
>>>>>>> +}
>>>>>>> +
>>>>>>> +/*
>>>>>>> + * Custom Software-Shutdown function for IS31FL3216 because it does not have
>>>>>>> + * a SHUTDOWN register the way that the other IS31FL32xx chips do.
>>>>>>> + * We don't bother doing a read/modify/write on the CONFIG register because
>>>>>>> + * we only ever use a value of '0' for the other fields in that register.
>>>>>>> + */
>>>>>>> +static int is31fl3216_software_shutdown(struct is31fl32xx_priv *priv,
>>>>>>> + bool enable)
>>>>>>> +{
>>>>>>> + u8 value = enable ? IS31FL3216_CONFIG_SSD_ENABLE :
>>>>>>> + IS31FL3216_CONFIG_SSD_DISABLE;
>>>>>>> +
>>>>>>> + return is31fl32xx_write(priv, IS31FL3216_CONFIG_REG, value);
>>>>>>> +}
>>>>>>> +
>>>>>>> +/*
>>>>>>> + * NOTE: A mutex is not needed in this function because:
>>>>>>> + * - All referenced data is read-only after probe()
>>>>>>> + * - The I2C core has a mutex on to protect the bus
>>>>>>> + * - There are no read/modify/write operations
>>>>>>> + * - Intervening operations between the write of the PWM register
>>>>>>> + * and the Update register are harmless.
>>>>>>> + *
>>>>>>> + * Example:
>>>>>>> + * PWM_REG_1 write 16
>>>>>>> + * UPDATE_REG write 0
>>>>>>> + * PWM_REG_2 write 128
>>>>>>> + * UPDATE_REG write 0
>>>>>>> + * vs:
>>>>>>> + * PWM_REG_1 write 16
>>>>>>> + * PWM_REG_2 write 128
>>>>>>> + * UPDATE_REG write 0
>>>>>>> + * UPDATE_REG write 0
>>>>>>> + * are equivalent. Poking the Update register merely applies all PWM
>>>>>>> + * register writes up to that point.
>>>>>>> + */
>>>>>>> +static int is31fl32xx_brightness_set(struct led_classdev *led_cdev,
>>>>>>> + enum led_brightness brightness)
>>>>>>> +{
>>>>>>> + const struct is31fl32xx_led_data *led_data =
>>>>>>> + container_of(led_cdev, struct is31fl32xx_led_data, cdev);
>>>>>>> + const struct is31fl32xx_chipdef *cdef = led_data->priv->cdef;
>>>>>>> + u8 pwm_register_offset;
>>>>>>> + int ret;
>>>>>>> +
>>>>>>> + dev_dbg(led_cdev->dev, "%s: %d\n", __func__, brightness);
>>>>>>> +
>>>>>>> + /* NOTE: led_data->channel is 1-based */
>>>>>>> + if (cdef->pwm_registers_reversed)
>>>>>>> + pwm_register_offset = cdef->channels - led_data->channel;
>>>>>>> + else
>>>>>>> + pwm_register_offset = led_data->channel - 1;
>>>>>>> +
>>>>>>> + ret = is31fl32xx_write(led_data->priv,
>>>>>>> + cdef->pwm_register_base + pwm_register_offset,
>>>>>>> + brightness);
>>>>>>> + if (ret)
>>>>>>> + return ret;
>>>>>>> +
>>>>>>> + return is31fl32xx_write(led_data->priv, cdef->pwm_update_reg, 0);
>>>>>>> +}
>>>>>>> +
>>>>>>> +static int is31fl32xx_reset_regs(struct is31fl32xx_priv *priv)
>>>>>>> +{
>>>>>>> + const struct is31fl32xx_chipdef *cdef = priv->cdef;
>>>>>>> + int ret;
>>>>>>> +
>>>>>>> + if (cdef->reset_reg != IS31FL32XX_REG_NONE) {
>>>>>>> + ret = is31fl32xx_write(priv, cdef->reset_reg, 0);
>>>>>>> + if (ret)
>>>>>>> + return ret;
>>>>>>> + }
>>>>>>> +
>>>>>>> + if (cdef->reset_func)
>>>>>>> + return cdef->reset_func(priv);
>>>>>>> +
>>>>>>> + return 0;
>>>>>>> +}
>>>>>>> +
>>>>>>> +static int is31fl32xx_software_shutdown(struct is31fl32xx_priv *priv,
>>>>>>> + bool enable)
>>>>>>> +{
>>>>>>> + const struct is31fl32xx_chipdef *cdef = priv->cdef;
>>>>>>> + int ret;
>>>>>>> +
>>>>>>> + if (cdef->shutdown_reg != IS31FL32XX_REG_NONE) {
>>>>>>> + u8 value = enable ? IS31FL32XX_SHUTDOWN_SSD_ENABLE :
>>>>>>> + IS31FL32XX_SHUTDOWN_SSD_DISABLE;
>>>>>>> + ret = is31fl32xx_write(priv, cdef->shutdown_reg, value);
>>>>>>> + if (ret)
>>>>>>> + return ret;
>>>>>>> + }
>>>>>>> +
>>>>>>> + if (cdef->sw_shutdown_func)
>>>>>>> + return cdef->sw_shutdown_func(priv, enable);
>>>>>>
>>>>>> You seem to call sw_shutdown_func only here, so why should we have
>>>>>> enable parameter in this op?
>>>>>
>>>>> I'm not sure if I understand the question, but I will try to answer.
>>>>>
>>>>> 'enable' is passed through is31fl32xx_software_shutdown to
>>>>> cdef->sw_shutdown_func, so it can be either true or false at that
>>>>> point. The purpose of sw_shutdown_func is to add any special behavior
>>>>> when enabling/disabling software-shutdown mode, which is needed for
>>>>> the 3216 because its SSD bit is in a different position and with
>>>>> opposite polarity.
>>>>>
>>>>> Is it that 'enable' in that line of code makes it look like it's being
>>>>> called with an hardcoded value rather than a variable? If so, perhaps a
>>>>> different parameter name would make it more obvious? Or a kerneldoc
>>>>> comment for the function to describe the parameter?
>>>>>
>>>>> Or have I totally missed the point of the question?
>>>>
>>>> Actually I should have placed this question next to
>>>> the call to s31fl32xx_software_shutdown() in is31fl32xx_init_regs(),
>>>> which is passed "false" in the second argument, and there is no
>>>> other call to s31fl32xx_software_shutdown() in the driver.
>>>>
>>>> Having the argument makes people wondering that there is some
>>>> use case in the driver, where "true" is passed, but it seems not
>>>> to be the case.
>>>
>>> Thanks for the clarification.
>>>
>>> Yes, there is currently no explicit call to enable software-shutdown
>>> mode. Since the reset state of these devices is to have software-shutdown
>>> enabled, the only explicit operation on it that's currently needed is
>>> to disable it.
>>>
>>> Reasons I can think to have the 'enable' parameter anyways include:
>>> - It seems logical to me that an API to manipulate the software-shutdown
>>> state should allow both enabling and disabling.
>>> - Having a parameter for that seemed the most obvious way to go, and it
>>> was trivial to implement.
>>> - Alternatively having separate "enable" and "disable" functions would
>>> duplicate most of the logic, vs the parameter being just a single
>>> conditional. And that would also imply two function pointers in the
>>> chipdefs, which I'd prefer to minimize.
>>> - If anyone wanted to implement suspend/resume in the future, they would
>>> most likely do it by enabling/disabling software-shutdown. Supporting
>>> both enable/disable from the start should make that trivial to do.
>>
>> Suspend/resume callbacks are already implemented in led-class.c and
>> related ops indirectly call brightness_set. If you want to support
>> suspend/resume you have to set LED_CORE_SUSPENDRESUME flag.
>
> If I understand correctly, all LED_CORE_SUSPENDRESUME will do is cause
> the led core to set the brightness to 0 on suspend (and reverse that
> on resume). I see some drivers use this flag and other do not.
> This brings up the question in my mind: how would a driver decide
> whether it is appropriate for an LED to go dark on suspend? Is that
> just the drivers that know the logical purpose of the LEDs they control?

There is a room for improvement here. Possibly a new LED class sysfs
attribute could be of help in determining that.

>> Setting brightness to 0 is equivalent to turning the LED controller
>> in a shutdown mode, provided that all sub-LEDs are off.
>
> This is not strictly true for these devices. If someone cared very much
> about power usage when suspended they may want to put the LED controller
> into what it calls "shutdown mode" via the SSD bit. I didn't bother mainly
> because I have no need, and also because I wasn't sure how to even trigger
> a suspend in order to test an implementation.

I meant that LED class driver should put the device in a software
shutdown mode after last sub-LED is turned off.

> FYI, I just measured it the effect of software-shutdown even with all LEDs
> already off. The difference in current is about 5mA, measured at the 5V
> supply to a 3216 eval board. Not huge, but someone might care.

This can be vital difference for some use cases. You could count the
number of currently active sub-LEDs and put the controller in a software
shutdown mode in case the value is 0.

>>> - I thought the code read better with a bool parameter, vs a longer
>>> function name.
>>>
>>> So nothing really critical, but mostly just my aesthetic and preference.
>>>
>>> Also, I expect that is31fl32xx_software_shutdown() would be inlined, so
>>> the conditional check in there is optimized out anyways, and there is no
>>> performance penalty. Looking at the disassembly in my ARMv7a build, both
>>> of those have indeed happened there.
>>
>> Not only the size of a binary and the performance, but also code
>> readability matters. The function is called only with false argument,
>> so I expect that some people may submit patches optimizing this.
>>
>> Let's avoid the confusion.
>
> I guess we just have a difference of opinion on which way is more
> readable, which is OK. Unless the above explanation causes you to
> change your mind, I will remove the 'enable' parameter and add a
> "_disable" suffix to both functions. That will also leave the
> #define IS31FL32XX_SHUTDOWN_SSD_ENABLE 0
> constant unused in the code, should that also be removed? Note that
> the 3216 specific constant
> #define IS31FL3216_CONFIG_SSD_ENABLE BIT(7)
> would still be used in is31fl3216_reset().

Current version of the function would be required for enabling
shutting down the controller from brightness_set op when the
count of active sub-LEDs drops to 0.

>>>>>>> + return 0;
>>>>>>> +}
>>>>>>> +
>>>>>>> +static int is31fl32xx_init_regs(struct is31fl32xx_priv *priv)
>>>>>>> +{
>>>>>>> + const struct is31fl32xx_chipdef *cdef = priv->cdef;
>>>>>>> + int ret;
>>>>>>> +
>>>>>>> + ret = is31fl32xx_reset_regs(priv);
>>>>>>> + if (ret)
>>>>>>> + return ret;
>>>>>>> +
>>>>>>> + /*
>>>>>>> + * Set enable bit for all channels.
>>>>>>> + * We will control state with PWM registers alone.
>>>>>>> + */
>>>>>>> + if (cdef->led_control_register_base != IS31FL32XX_REG_NONE) {
>>>>>>> + u8 value =
>>>>>>> + GENMASK(cdef->enable_bits_per_led_control_register-1, 0);
>>>>>>> + u8 num_regs = cdef->channels /
>>>>>>> + cdef->enable_bits_per_led_control_register;
>>>>>>> + int i;
>>>>>>> +
>>>>>>> + for (i = 0; i < num_regs; i++) {
>>>>>>> + ret = is31fl32xx_write(priv,
>>>>>>> + cdef->led_control_register_base+i,
>>>>>>> + value);
>>>>>>> + if (ret)
>>>>>>> + return ret;
>>>>>>> + }
>>>>>>> + }
>>>>>>> +
>>>>>>> + ret = is31fl32xx_software_shutdown(priv, false);
>>>>>>> + if (ret)
>>>>>>> + return ret;
>>>>>>> +
>>>>>>> + if (cdef->global_control_reg != IS31FL32XX_REG_NONE) {
>>>>>>> + ret = is31fl32xx_write(priv, cdef->global_control_reg, 0x00);
>>>>>>> + if (ret)
>>>>>>> + return ret;
>>>>>>> + }
>>>>>>> +
>>>>>>> + return 0;
>>>>>>> +}
>>>>>>> +
>>>>>>> +static inline size_t sizeof_is31fl32xx_priv(int num_leds)
>>>>>>> +{
>>>>>>> + return sizeof(struct is31fl32xx_priv) +
>>>>>>> + (sizeof(struct is31fl32xx_led_data) * num_leds);
>>>>>>> +}
>>>>>>> +
>>>>>>> +static int is31fl32xx_parse_child_dt(const struct device *dev,
>>>>>>> + const struct device_node *child,
>>>>>>> + struct is31fl32xx_led_data *led_data)
>>>>>>> +{
>>>>>>> + struct led_classdev *cdev = &led_data->cdev;
>>>>>>> + int ret = 0;
>>>>>>> + u32 reg;
>>>>>>> +
>>>>>>> + if (of_property_read_string(child, "label", &cdev->name))
>>>>>>> + cdev->name = child->name;
>>>>>>> +
>>>>>>> + ret = of_property_read_u32(child, "reg", &reg);
>>>>>>> + if (ret || reg < 1 || reg > led_data->priv->cdef->channels) {
>>>>>>> + dev_err(dev,
>>>>>>> + "Child node %s does not have a valid reg property\n",
>>>>>>> + child->full_name);
>>>>>>> + return -EINVAL;
>>>>>>> + }
>>>>>>> + led_data->channel = reg;
>>>>>>> +
>>>>>>> + of_property_read_string(child, "linux,default-trigger",
>>>>>>> + &cdev->default_trigger);
>>>>>>> +
>>>>>>> + cdev->brightness_set_blocking = is31fl32xx_brightness_set;
>>>>>>> +
>>>>>>> + return 0;
>>>>>>> +}
>>>>>>> +
>>>>>>> +static struct is31fl32xx_led_data *is31fl32xx_find_led_data(
>>>>>>> + struct is31fl32xx_priv *priv,
>>>>>>> + u8 channel)
>>>>>>> +{
>>>>>>> + size_t i;
>>>>>>> +
>>>>>>> + for (i = 0; i < priv->num_leds; i++) {
>>>>>>> + if (priv->leds[i].channel == channel)
>>>>>>> + return &priv->leds[i];
>>>>>>> + }
>>>>>>> +
>>>>>>> + return NULL;
>>>>>>> +}
>>>>>>> +
>>>>>>> +static int is31fl32xx_parse_dt(struct device *dev,
>>>>>>> + struct is31fl32xx_priv *priv)
>>>>>>> +{
>>>>>>> + struct device_node *child;
>>>>>>> + int ret = 0;
>>>>>>> +
>>>>>>> + for_each_child_of_node(dev->of_node, child) {
>>>>>>> + struct is31fl32xx_led_data *led_data =
>>>>>>> + &priv->leds[priv->num_leds];
>>>>>>> + const struct is31fl32xx_led_data *other_led_data;
>>>>>>> +
>>>>>>> + led_data->priv = priv;
>>>>>>> +
>>>>>>> + ret = is31fl32xx_parse_child_dt(dev, child, led_data);
>>>>>>> + if (ret)
>>>>>>> + goto err;
>>>>>>> +
>>>>>>> + /* Detect if channel is already in use by another child */
>>>>>>> + other_led_data = is31fl32xx_find_led_data(priv,
>>>>>>> + led_data->channel);
>>>>>>> + if (other_led_data) {
>>>>>>> + dev_err(dev,
>>>>>>> + "%s and %s both attempting to use channel %d\n",
>>>>>>> + led_data->cdev.name,
>>>>>>> + other_led_data->cdev.name,
>>>>>>> + led_data->channel);
>>>>>>> + goto err;
>>>>>>> + }
>>>>>>> +
>>>>>>> + ret = devm_led_classdev_register(dev, &led_data->cdev);
>>>>>>> + if (ret) {
>>>>>>> + dev_err(dev, "failed to register PWM led for %s: %d\n",
>>>>>>> + led_data->cdev.name, ret);
>>>>>>> + goto err;
>>>>>>> + }
>>>>>>> +
>>>>>>> + priv->num_leds++;
>>>>>>> + }
>>>>>>> +
>>>>>>> + return 0;
>>>>>>> +
>>>>>>> +err:
>>>>>>> + of_node_put(child);
>>>>>>> + return ret;
>>>>>>> +}
>>>>>>> +
>>>>>>> +static const struct of_device_id of_is31fl31xx_match[] = {
>>>>>>> + { .compatible = "issi,is31fl3236", .data = &is31fl3236_cdef, },
>>>>>>> + { .compatible = "issi,is31fl3235", .data = &is31fl3235_cdef, },
>>>>>>> + { .compatible = "issi,is31fl3218", .data = &is31fl3218_cdef, },
>>>>>>> + { .compatible = "issi,is31fl3216", .data = &is31fl3216_cdef, },
>>>>>>> + {},
>>>>>>> +};
>>>>>>> +
>>>>>>> +MODULE_DEVICE_TABLE(of, of_is31fl31xx_match);
>>>>>>> +
>>>>>>> +static int is31fl32xx_probe(struct i2c_client *client,
>>>>>>> + const struct i2c_device_id *id)
>>>>>>> +{
>>>>>>> + const struct is31fl32xx_chipdef *cdef;
>>>>>>> + const struct of_device_id *of_dev_id;
>>>>>>> + struct device *dev = &client->dev;
>>>>>>> + struct is31fl32xx_priv *priv;
>>>>>>> + int count;
>>>>>>> + int ret = 0;
>>>>>>> +
>>>>>>> + of_dev_id = of_match_device(of_is31fl31xx_match, dev);
>>>>>>> + if (!of_dev_id)
>>>>>>> + return -EINVAL;
>>>>>>> +
>>>>>>> + cdef = of_dev_id->data;
>>>>>>> +
>>>>>>> + count = of_get_child_count(dev->of_node);
>>>>>>> + if (!count)
>>>>>>> + return -EINVAL;
>>>>>>> +
>>>>>>> + priv = devm_kzalloc(dev, sizeof_is31fl32xx_priv(count),
>>>>>>> + GFP_KERNEL);
>>>>>>> + if (!priv)
>>>>>>> + return -ENOMEM;
>>>>>>> +
>>>>>>> + priv->client = client;
>>>>>>> + priv->cdef = cdef;
>>>>>>> + i2c_set_clientdata(client, priv);
>>>>>>> +
>>>>>>> + ret = is31fl32xx_init_regs(priv);
>>>>>>> + if (ret)
>>>>>>> + return ret;
>>>>>>> +
>>>>>>> + ret = is31fl32xx_parse_dt(dev, priv);
>>>>>>> + if (ret)
>>>>>>> + return ret;
>>>>>>> +
>>>>>>> + return 0;
>>>>>>> +}
>>>>>>> +
>>>>>>> +static int is31fl32xx_remove(struct i2c_client *client)
>>>>>>> +{
>>>>>>> + struct is31fl32xx_priv *priv = i2c_get_clientdata(client);
>>>>>>> +
>>>>>>> + return is31fl32xx_reset_regs(priv);
>>>>>>> +}
>>>>>>> +
>>>>>>> +/*
>>>>>>> + * i2c-core requires that id_table be non-NULL, even though
>>>>>>> + * it is not used for DeviceTree based instantiation.
>>>>>>> + */
>>>>>>> +static const struct i2c_device_id is31fl31xx_id[] = {
>>>>>>> + {},
>>>>>>> +};
>>>>>>> +
>>>>>>> +MODULE_DEVICE_TABLE(i2c, is31fl31xx_id);
>>>>>>> +
>>>>>>> +static struct i2c_driver is31fl32xx_driver = {
>>>>>>> + .driver = {
>>>>>>> + .name = "is31fl32xx",
>>>>>>> + .of_match_table = of_is31fl31xx_match,
>>>>>>> + },
>>>>>>> + .probe = is31fl32xx_probe,
>>>>>>> + .remove = is31fl32xx_remove,
>>>>>>> + .id_table = is31fl31xx_id,
>>>>>>> +};
>>>>>>> +
>>>>>>> +module_i2c_driver(is31fl32xx_driver);
>>>>>>> +
>>>>>>> +MODULE_AUTHOR("David Rivshin <drivshin@allworx.com>");
>>>>>>> +MODULE_DESCRIPTION("ISSI IS31FL32xx LED driver");
>>>>>>> +MODULE_LICENSE("GPL v2");
>>>>>>>
>
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>

--
Best Regards,
Jacek Anaszewski