[Letux-kernel] [PATCH] drivers: led: is31fl319x: 6/9-channel light effect led driver

Jacek Anaszewski jacek.anaszewski at gmail.com
Wed Apr 20 23:03:05 CEST 2016


Hi Nikolaus,

On 04/19/2016 07:21 PM, H. Nikolaus Schaller wrote:
> Hi Jacek,
>
>> Am 19.04.2016 um 11:14 schrieb Jacek Anaszewski <j.anaszewski at samsung.com>:
>>
>> Hi Nikolaus,
>>
>> Thanks for the patch. Please refer to my remarks in the code.
>
> Thanks for the remarks!

You're welcome.

>>
>> On 04/18/2016 08:43 PM, H. Nikolaus Schaller wrote:
>>> This is a driver for the Integrated Silicon Solution Inc. LED driver
>>> chips IS31FL3196 and IS31FL3199. They can drive up to 6 or 9
>>> LEDs.
>>>
>>> Each LED is individually controllable in brightness (through pwm)
>>> in 256 steps so that RGB LEDs can show any of ca. 16 Mio colors.
>>>
>>> The maximum current of the LEDs can be programmed and limited to
>>> 5 .. 40mA through a device tree property.
>>>
>>> The chip is connected through I2C and can have one of 4 addresses (0x64 .. 0x67)
>>> depending on how the AD pin is connected. The address is defined by the
>>> reg property as usual.
>>>
>>> The chip also has a shutdown input which could be connected to a GPIO,
>>> but this driver uses software shutdown if all LEDs are inactivated.
>>>
>>> The chip also has breathing and audio features which are not supported
>>> by this driver.
>>>
>>> This driver was developed and tested on OMAP5 based Pyra handheld prototype.
>>>
>>> Signed-off-by: H. Nikolaus Schaller <hns at goldelico.com>
>>> ---
>>>   .../devicetree/bindings/leds/is31fl319x.txt        |  41 +++
>>>   drivers/leds/Kconfig                               |   8 +
>>>   drivers/leds/Makefile                              |   1 +
>>>   drivers/leds/leds-is31fl319x.c                     | 406 +++++++++++++++++++++
>>>   include/linux/leds-is31fl319x.h                    |  24 ++
>>>   5 files changed, 480 insertions(+)
>>>   create mode 100644 Documentation/devicetree/bindings/leds/is31fl319x.txt
>>>   create mode 100644 drivers/leds/leds-is31fl319x.c
>>>   create mode 100644 include/linux/leds-is31fl319x.h
>>>
>>> diff --git a/Documentation/devicetree/bindings/leds/is31fl319x.txt b/Documentation/devicetree/bindings/leds/is31fl319x.txt
>>> new file mode 100644
>>> index 0000000..d13c7ca
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/leds/is31fl319x.txt
>>> @@ -0,0 +1,41 @@
>>> +LEDs connected to is31fl319x RGB LED controller chip
>>> +
>>> +Required properties:
>>> +- compatible : should be : "issi,is31fl3196" or "issi,is31fl3199".
>>
>> s/should be :/Should be/
>
> done.
>
>>
>>> +- #address-cells: must be 1
>>> +- #size-cells: must be 0
>>
>> s/must/Must/
>>
>> Please begin the property description with a capital letter,
>> and also end it with a dot.
>> This remark applies also to the other properties.
>
> Done.
>
>>
>>> +- reg: 0x64, 0x65, 0x66, 0x67.
>>> +
>>> +Optional properties:
>>> +- max-current-ma:	maximum led current (5..40 mA, default 20 mA)
>>
>> There is leds-max-microamp property for this -
>> see Documentation/devicetree/bindings/leds/common.txt.
>
> Ah, I wasn't aware that this property should also apply to the whole chip (in that
> document it is described as a property for each individual LED).

It is indented for individual LEDs. I missed that you defined it for
the whole chip. The property, when present, should have an impact on the
max_brightness property of the struct led_classdev.

> Renamed.
>
>> I'd rephrase this as follows:
>>
>> - led-max-microamp: See Documentation/devicetree/bindings/leds/common.txt.
>>         Valid values: 50000 - 400000, step by (?) (rounded {up|down})
>>         Default: 20000
>>
>>> +- audio-gain-db:	audio gain selection (0..21 dB. default 0 dB)
>>
>> Please follow the aforementioned "Valid values" pattern.
>> It would also be nice to have more informative description on the
>> purpose of this property.
>
> Done.
>
>>
>>> +- breathing & audio:	not implemented
>>
>> There is no point in documenting unused properties.
>
> Done.
>
>>
>>> +
>>> +Each led is represented as a sub-node of the issi,is31fl319x device.
>>> +
>>> +LED sub-node properties:
>>> +- label : (optional) see Documentation/devicetree/bindings/leds/common.txt
>>> +- reg : number of LED line (0 to 5 or 0 to 8 - not all need to be present)
>>> +- linux,default-trigger : (optional)
>>> +   see Documentation/devicetree/bindings/leds/common.txt
>>> +
>>> +Examples:
>>> +
>>> +fancy_leds: is31fl3196 at 65 {
>>> +	compatible = "issi,is31fl319x";
>>> +	#address-cells = <1>;
>>> +	#size-cells = <0>;
>>> +	reg = <0x65>;
>>> +
>>> +	led0: red-aux at 0 {
>>> +		label = "red:aux";
>>> +		reg = <0>;
>>> +	};
>>> +
>>> +	led1: green-power at 4 {
>>> +		label = "green:power";
>>> +		reg = <4>;
>>> +		linux,default-trigger = "default-on";
>>> +	};
>>> +};
>>
>> Generally I prefer to have DT bindings documentation in a separate
>> patch.
>
> Yes, you are right and not only you prefer it :)
> It just gets forgotten for such simple drivers...
>
>>
>>> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
>>> index 2251478..f099bcb 100644
>>> --- a/drivers/leds/Kconfig
>>> +++ b/drivers/leds/Kconfig
>>> @@ -491,6 +491,14 @@ config LEDS_ASIC3
>>>   	  cannot be used. This driver supports hardware blinking with an on+off
>>>   	  period from 62ms to 125s. Say Y to enable LEDs on the HP iPAQ hx4700.
>>>
>>> +config LEDS_IS31FL319X
>>> +	tristate "LED Support for IS31FL319x I2C chip"
>>> +	depends on LEDS_CLASS && I2C
>>> +	help
>>> +	  This option enables support for LEDs connected to IS31FL3196
>>> +	  or IS31FL3199 LED driver chips accessed via the I2C bus.
>>> +	  Driver support brightness control and hardware-assisted blinking.
>>> +
>>>   config LEDS_TCA6507
>>>   	tristate "LED Support for TCA6507 I2C chip"
>>>   	depends on LEDS_CLASS && I2C
>>> diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
>>> index cb2013d..eee3010 100644
>>> --- a/drivers/leds/Makefile
>>> +++ b/drivers/leds/Makefile
>>> @@ -37,6 +37,7 @@ obj-$(CONFIG_LEDS_TCA6507)		+= leds-tca6507.o
>>>   obj-$(CONFIG_LEDS_TLC591XX)		+= leds-tlc591xx.o
>>>   obj-$(CONFIG_LEDS_CLEVO_MAIL)		+= leds-clevo-mail.o
>>>   obj-$(CONFIG_LEDS_IPAQ_MICRO)		+= leds-ipaq-micro.o
>>> +obj-$(CONFIG_LEDS_IS31FL319X)		+= leds-is31fl319x.o
>>>   obj-$(CONFIG_LEDS_HP6XX)		+= leds-hp6xx.o
>>>   obj-$(CONFIG_LEDS_OT200)		+= leds-ot200.o
>>>   obj-$(CONFIG_LEDS_FSG)			+= leds-fsg.o
>>> diff --git a/drivers/leds/leds-is31fl319x.c b/drivers/leds/leds-is31fl319x.c
>>> new file mode 100644
>>> index 0000000..e211c46
>>> --- /dev/null
>>> +++ b/drivers/leds/leds-is31fl319x.c
>>> @@ -0,0 +1,406 @@
>>> +/*
>>> + * Copyright 2015 Golden Delcious Computers
>>> + *
>>> + * Author: Nikolaus Schaller <hns at goldelico.com>
>>> + *
>>> + * Based on leds-tca6507.c
>>> + *
>>> + * This file is subject to the terms and conditions of version 2 of
>>> + * the GNU General Public License.  See the file COPYING in the main
>>> + * directory of this archive for more details.
>>> + *
>>> + * LED driver for the IS31FL3196/99 to drive 6 or 9 light effect LEDs.
>>> + *
>>> + */
>>> +
>>> +#include <linux/module.h>
>>> +#include <linux/slab.h>
>>> +#include <linux/leds.h>
>>> +#include <linux/err.h>
>>> +#include <linux/i2c.h>
>>> +#include <linux/workqueue.h>
>>> +#include <linux/leds-is31fl319x.h>
>>> +#include <linux/of.h>
>>
>> Please keep include directives in an alphabetical order.
>
> Done.
>
>>
>>> +
>>> +/* register numbers */
>>> +#define IS31FL319X_SHUTDOWN	0x00
>>> +#define IS31FL319X_CTRL1	0x01
>>> +#define IS31FL319X_CTRL2	0x02
>>> +#define IS31FL319X_CONFIG1	0x03
>>> +#define IS31FL319X_CONFIG2	0x04
>>> +#define IS31FL319X_RAMP_MODE	0x05
>>> +#define IS31FL319X_BREATH_MASK	0x06
>>> +#define IS31FL319X_PWM1		0x07
>>> +#define IS31FL319X_PWM2		0x08
>>> +#define IS31FL319X_PWM3		0x09
>>> +#define IS31FL319X_PWM4		0x0a
>>> +#define IS31FL319X_PWM5		0x0b
>>> +#define IS31FL319X_PWM6		0x0c
>>> +#define IS31FL319X_PWM7		0x0d
>>> +#define IS31FL319X_PWM8		0x0e
>>> +#define IS31FL319X_PWM9		0x0f
>>> +#define IS31FL319X_DATA_UPDATE	0x10
>>> +#define IS31FL319X_T0_1		0x11
>>> +#define IS31FL319X_T0_2		0x12
>>> +#define IS31FL319X_T0_3		0x13
>>> +#define IS31FL319X_T0_4		0x14
>>> +#define IS31FL319X_T0_5		0x15
>>> +#define IS31FL319X_T0_6		0x16
>>> +#define IS31FL319X_T0_7		0x17
>>> +#define IS31FL319X_T0_8		0x18
>>> +#define IS31FL319X_T0_9		0x19
>>> +#define IS31FL319X_T123_1	0x1a
>>> +#define IS31FL319X_T123_2	0x1b
>>> +#define IS31FL319X_T123_3	0x1c
>>> +#define IS31FL319X_T4_1		0x1d
>>> +#define IS31FL319X_T4_2		0x1e
>>> +#define IS31FL319X_T4_3		0x1f
>>> +#define IS31FL319X_T4_4		0x20
>>> +#define IS31FL319X_T4_5		0x21
>>> +#define IS31FL319X_T4_6		0x22
>>> +#define IS31FL319X_T4_7		0x23
>>> +#define IS31FL319X_T4_8		0x24
>>> +#define IS31FL319X_T4_9		0x25
>>> +#define IS31FL319X_TIME_UPDATE	0x26
>>> +
>>> +#define	IS31FL319X_REG_CNT	(IS31FL319X_TIME_UPDATE + 1)
>>> +
>>> +#define NUM_LEDS 9	/* max for 3199 chip */
>>> +
>>> +struct is31fl319x_chip {
>>> +	struct i2c_client	*client;
>>> +	struct work_struct	work;
>>> +	bool			work_scheduled;
>>> +	spinlock_t		lock;
>>> +	u8			reg_file[IS31FL319X_REG_CNT];
>>> +
>>> +	struct is31fl319x_led {
>>> +		struct is31fl319x_chip	*chip;
>>> +		struct led_classdev	led_cdev;
>>> +	} leds[NUM_LEDS];
>>> +};
>>> +
>>> +static const struct i2c_device_id is31fl319x_id[] = {
>>> +	{ "is31fl3196", 6 },
>>> +	{ "is31fl3196", 9 },
>>> +	{ }
>>> +};
>>> +MODULE_DEVICE_TABLE(i2c, is31fl319x_id);
>>> +
>>> +
>>> +static int is31fl319x_write(struct is31fl319x_chip *is31, u8 reg, u8 byte)
>>> +{
>>> +	struct i2c_client *cl = is31->client;
>>> +
>>> +	if (reg >= IS31FL319X_REG_CNT)
>>> +		return -EIO;
>>> +	is31->reg_file[reg] = byte;	/* save in cache */
>>> +	dev_dbg(&is31->client->dev, "write %02x to reg %02x\n", byte, reg);
>>> +	return i2c_smbus_write_byte_data(cl, reg, byte);
>>> +}
>>> +
>>> +static int is31fl319x_read(struct is31fl319x_chip *is31, u8 reg)
>>> +{
>>> +	if (reg >= IS31FL319X_REG_CNT)
>>> +		return -EIO;
>>> +	return is31->reg_file[reg];	/* read crom cache (can't read chip) */
>>> +}
>>> +
>>> +static void is31fl319x_work(struct work_struct *work)
>>> +{
>>> +	struct is31fl319x_chip *is31 = container_of(work,
>>> +						    struct is31fl319x_chip,
>>> +						    work);
>>> +	unsigned long flags;
>>> +	int i;
>>> +	u8 ctrl1, ctrl2;
>>> +
>>> +	dev_dbg(&is31->client->dev, "work called\n");
>>> +
>>> +	spin_lock_irqsave(&is31->lock, flags);
>>> +	/* make subsequent changes run another schedule_work */
>>> +	is31->work_scheduled = false;
>>> +	spin_unlock_irqrestore(&is31->lock, flags);
>>> +
>>> +	dev_dbg(&is31->client->dev, "write to chip\n");
>>> +
>>> +	ctrl1 = 0;
>>> +	ctrl2 = 0;
>>> +
>>> +	for (i = 0; i < NUM_LEDS; i++) {
>>> +		struct led_classdev *led = &is31->leds[i].led_cdev;
>>> +		bool on;
>>> +
>>> +		if (!is31->leds[i].led_cdev.name)
>>> +			continue;
>>> +
>>> +		dev_dbg(&is31->client->dev, "set brightness %u for led %u\n",
>>> +					    led->brightness, i);
>>> +
>>> +		/* update brightness register */
>>> +		is31fl319x_write(is31, IS31FL319X_PWM1 + i, led->brightness);
>>> +
>>> +		/* update output enable bits */
>>> +		on = led->brightness > LED_OFF;
>>
>> It's more common to achieve the same in the following way:
>>
>>                 on = !!led->brightness;
>
> Hm. This is quite difficult to understand and assumes that LED_OFF is 0.

Because LED_OFF is 0. See include/linux/leds.h.

> If find brightness > LED_OFF much more readable.

This is a matter of taste. We have already few occurrences of "!!"
use in the LED subsystem in similar context. It is also prevailing
throughout the whole kernel.

>>
>>> +		if (i < 3)
>>> +			ctrl1 |= on << i;	/* 0..2 => bit 0..2 */
>>> +		else if (i < 6)
>>> +			ctrl1 |= on << (i+1);	/* 3..5 => bit 4..6 */
>>> +		else
>>> +			ctrl2 |= on << (i-6);	/* 6..8 => bit 0..2 */
>>> +	}
>>
>> Why are you iterating over all sub-LEDs? One LED class device should
>> control single sub-LED/iout.
>
> Because they share two common control registers which are updated
> in one batch (instead of individual read-modify-write which introduces race issues).

Could you share some details about those races?

>
> And to properly control chip shutdown (code below) we must know when the last
> LED was set to brightness 0. This means we have to loop over them anyways
> to get the aggregate state of all LEDs.

The driver knows the actual state of the device, doesn't it?
Why should it retrieve the information back from the device?
It knows what it has written to. That is what the regmap relies
on. AFAIR regmap_read doesn't perform physical read from the device,
but returns the value cached on last regmap_write(), unless the register
is marked volatile.

> This is also the reason why I am hesitating to switch to the brand new
> brightness_set_blocking which appears to assume that each LED can and shall
> be controlled independently by independent i2c write commands. It could here,
> except for shutting down the chip if all LEDs are off (which is different from setting
> PWM to 0 for all LEDs). So this would probably increase I2C traffic compared to
> our batch mode (if any number of LEDs is modified since the last one, we trigger
> only a single i2c transaction for all LEDs).

Could you specify what is the batch mode, and where it is implemented in
the driver?

>>
>>> +
>>> +	/* check if any PWM is enabled or all outputs are now off */
>>> +	if (ctrl1 > 0 || ctrl2 > 0) {
>>> +		dev_dbg(&is31->client->dev, "power up\n");
>>> +		is31fl319x_write(is31, IS31FL319X_CTRL1, ctrl1);
>>> +		is31fl319x_write(is31, IS31FL319X_CTRL2, ctrl2);
>>> +		/* update PWMs */
>>> +		is31fl319x_write(is31, IS31FL319X_DATA_UPDATE, 0x00);
>>> +		/* enable chip from shut down */
>>> +		is31fl319x_write(is31, IS31FL319X_SHUTDOWN, 0x01);
>>> +	} else {
>>> +		dev_dbg(&is31->client->dev, "power down\n");
>>> +		/* shut down */
>>> +		is31fl319x_write(is31, IS31FL319X_SHUTDOWN, 0x00);
>>> +	}
>>> +
>>> +	dev_dbg(&is31->client->dev, "work done\n");
>>> +
>>> +}
>>> +
>>> +/* NOTE: this may be called from within irq context, e.g. led_trigger_event */
>>> +
>>> +static int is31fl319x_brightness_get(struct led_classdev *led_cdev)
>>> +{
>>> +	struct is31fl319x_led *led = container_of(led_cdev,
>>> +						  struct is31fl319x_led,
>>> +						  led_cdev);
>>> +	struct is31fl319x_chip *is31 = led->chip;
>>> +
>>> +	/* read PWM register */
>>> +	return is31fl319x_read(is31, IS31FL319X_PWM1 + (led - is31->leds));
>>> +}
>>> +
>>> +static void is31fl319x_brightness_set(struct led_classdev *led_cdev,
>>> +				   enum led_brightness brightness)
>>> +{
>>> +	struct is31fl319x_led *led = container_of(led_cdev,
>>> +						  struct is31fl319x_led,
>>> +						  led_cdev);
>>> +	struct is31fl319x_chip *is31 = led->chip;
>>> +	unsigned long flags;
>>> +
>>> +	spin_lock_irqsave(&is31->lock, flags);
>>> +
>>> +	if (brightness != is31fl319x_brightness_get(led_cdev)) {
>>
>> Current brightness is cached in led_cdev->brightness.
>
> Hm. I could not find the code line where it is cached.

The first line in led_set_brightness_nosleep()
(drivers/leds/led-core.c).
But it is cached before the call to brightness_set op,
so it wouldn't be useful in your approach.

Nevertheless I don't think you need to check the old
brightness by performing I2C readout. You can cache it
on write. You don't need to reinvent the wheel, but use
very flexible regmap feature, though.

>
> And if I remember correctly (it is a while ago that we did develop
> this driver) experiments didn't show that it is cached there. Or the
> old value is not available inside the brightness setter but already
> the new one. Something like that was the reason why we cache
> it inside the driver.
>
>>
>>> +		if (!is31->work_scheduled) {
>>> +			schedule_work(&is31->work);
>>> +			is31->work_scheduled = true;
>>> +		}
>>> +	}
>>> +
>>> +	spin_unlock_irqrestore(&is31->lock, flags);
>>> +}
>>> +
>>> +static int is31fl319x_blink_set(struct led_classdev *led_cdev,
>>> +			     unsigned long *delay_on,
>>> +			     unsigned long *delay_off)
>>> +{
>>> +	/* use software blink */
>>> +	return 1;
>>> +}
>>
>> This function is useless, please remove it.
>
> Ok.
>
>>
>>> +#ifdef CONFIG_OF
>>
>> Please provide only version for CONFIG_OF defined case and just fail
>> probing if of_node is NULL.
>
> Ok.
>
>>
>>> +static struct is31fl319x_platform_data *
>>> +is31fl319x_led_dt_init(struct i2c_client *client, int num_leds)
>>
>> Please rename it to is31fl319x_parse_dt.
>
> Done.
>
>>
>>> +{
>>> +	struct device_node *np = client->dev.of_node, *child;
>>> +	struct is31fl319x_platform_data *pdata;
>>> +	struct led_info *is31_leds;
>>> +	int count;
>>> +
>>> +	count = of_get_child_count(np);
>>> +	dev_dbg(&client->dev, "child count %d\n", count);
>>> +	if (!count || count > NUM_LEDS)
>>> +		return ERR_PTR(-ENODEV);
>>> +
>>> +	is31_leds = devm_kzalloc(&client->dev,
>>> +			sizeof(struct led_info) * NUM_LEDS, GFP_KERNEL);
>>> +	if (!is31_leds)
>>> +		return ERR_PTR(-ENOMEM);
>>> +
>>> +	for_each_child_of_node(np, child) {
>>> +		struct led_info led;
>>> +		u32 reg;
>>> +		int ret;
>>> +
>>> +		led.name =
>>> +			of_get_property(child, "label", NULL) ? : child->name;
>>> +		led.default_trigger =
>>> +			of_get_property(child, "linux,default-trigger", NULL);
>>> +		led.flags = 0;
>>> +		ret = of_property_read_u32(child, "reg", &reg);
>>> +		dev_dbg(&client->dev, "name = %s reg = %d\n", led.name, reg);
>>> +		if (ret != 0 || reg < 0 || reg >= num_leds)
>>> +			continue;
>>> +
>>> +		if (is31_leds[reg].name)
>>> +			dev_err(&client->dev, "duplicate led line %d for %s -> %s\n",
>>> +				reg, is31_leds[reg].name, led.name);
>>> +		is31_leds[reg] = led;
>>> +	}
>>> +	pdata = devm_kzalloc(&client->dev,
>>> +			sizeof(struct is31fl319x_platform_data), GFP_KERNEL);
>>> +	if (!pdata)
>>> +		return ERR_PTR(-ENOMEM);
>>> +
>>> +	pdata->leds.leds = is31_leds;
>>> +	return pdata;
>>> +}
>>> +
>>> +static const struct of_device_id of_is31fl319x_leds_match[] = {
>>> +	{ .compatible = "issi,is31fl3196", (void *) 6 },
>>> +	{ .compatible = "issi,is31fl3199", (void *) 9 },
>>> +	{},
>>> +};
>>> +MODULE_DEVICE_TABLE(of, of_is31fl319x_leds_match);
>>> +
>>> +#else
>>> +static struct is31fl319x_platform_data *
>>> +is31fl319x_led_dt_init(struct i2c_client *client)
>>> +{
>>> +	return ERR_PTR(-ENODEV);
>>> +}
>>> +
>>> +#endif
>>> +
>>> +static int is31fl319x_probe(struct i2c_client *client,
>>> +		const struct i2c_device_id *id)
>>> +{
>>> +	struct is31fl319x_chip *is31;
>>> +	struct i2c_adapter *adapter;
>>> +	struct is31fl319x_platform_data *pdata;
>>> +	int err;
>>> +	int i = 0;
>>> +
>>> +	adapter = to_i2c_adapter(client->dev.parent);
>>> +	pdata = dev_get_platdata(&client->dev);
>>> +
>>> +	dev_dbg(&client->dev, "probe\n");
>>> +
>>> +	dev_dbg(&client->dev, "NUM_LEDS = %d num_leds = %d\n",
>>> +		NUM_LEDS, (int) id->driver_data);
>>
>> I believe this is stray debug logging.
>
> I have merged it with the probe debug message to give more useful information.
>
>>
>>> +
>>> +	if (!i2c_check_functionality(adapter, I2C_FUNC_I2C))
>>> +		return -EIO;
>>> +
>>> +	if (!pdata) {
>>> +		pdata = is31fl319x_led_dt_init(client, (int) id->driver_data);
>>> +		if (IS_ERR(pdata)) {
>>> +			dev_err(&client->dev, "DT led error %d\n",
>>
>> s/DT led error/DT parsing error/
>
> done.
>
>>
>>> +				(int) PTR_ERR(pdata));
>>> +			return PTR_ERR(pdata);
>>> +		}
>>> +	}
>>> +	is31 = devm_kzalloc(&client->dev, sizeof(*is31), GFP_KERNEL);
>>> +	if (!is31)
>>> +		return -ENOMEM;
>>> +
>>> +	is31->client = client;
>>> +	INIT_WORK(&is31->work, is31fl319x_work);
>>> +	spin_lock_init(&is31->lock);
>>> +	i2c_set_clientdata(client, is31);
>>> +
>>> +	/* check for reply from chip (we can't read any registers) */
>>> +	err = is31fl319x_write(is31, IS31FL319X_SHUTDOWN, 0x01);
>>> +	if (err < 0) {
>>> +		dev_err(&client->dev, "no response from chip write: err = %d\n",
>>> +			err);
>>> +		return -EPROBE_DEFER;	/* does not answer (yet) */
>>
>> When can it happen? Does the chip have a long booting time or so?
>
> Hm. Rarely...
>
> So if it is not available on first attempt, there is no reason to probe later.
>
> I will make it return -EIO.
>
>>
>>> +	}
>>> +
>>> +	for (i = 0; i < NUM_LEDS; i++) {
>>> +		struct is31fl319x_led *l = is31->leds + i;
>>> +
>>> +		l->chip = is31;
>>> +		if (pdata->leds.leds[i].name && !pdata->leds.leds[i].flags) {
>>> +			l->led_cdev.name = pdata->leds.leds[i].name;
>>> +			l->led_cdev.default_trigger
>>> +				= pdata->leds.leds[i].default_trigger;
>>> +			l->led_cdev.brightness_set = is31fl319x_brightness_set;
>
>>> +			l->led_cdev.blink_set = is31fl319x_blink_set;
>>> +			err = led_classdev_register(&client->dev,
>>> +						    &l->led_cdev);
>>> +			if (err < 0)
>>> +				goto exit;
>>> +		}
>>> +	}
>>> +
>>> +	if (client->dev.of_node) {
>>> +		u32 val;
>>> +		u8 config2 = 0;
>>> +
>>> +		if (of_property_read_u32(client->dev.of_node, "max-current-ma",
>>> +					 &val)) {
>>> +			if (val > 40)
>>> +				val = 40;
>>> +			if (val < 5)
>>> +				val = 5;
>>> +			config2 |= (((64 - val) / 5) & 0x7) << 4; /* CS */
>>> +		}
>>> +		if (of_property_read_u32(client->dev.of_node, "audio-gain-db",
>>> +					 &val)) {
>>> +			if (val > 21)
>>> +				val = 21;
>>> +			config2 |= val / 3; /* AGS */
>>> +		}
>>> +		if (config2)
>>> +			is31fl319x_write(is31, IS31FL319X_CONFIG2, config2);
>>> +	}
>>
>> Could you move the contents of this condition to is31fl319x_led_dt_init?
>
> What would that improve?

Code readability? Having DT parsing in a single place is a good
practice.

> It is intended as a timing optimization to skip the i2c write.
 >
> With the implicit assumption that the register is already initialized to 0.
>
> Which I know think is not always the case. The chip might already be initialized by
> U-Boot or after a reboot when it was not powered down.
>
> So I think the condition must be removed completely.
>
>>
>>> +
>>> +	schedule_work(&is31->work);	/* first update */
>>> +
>>> +	dev_dbg(&client->dev, "probed\n");
>>> +	return 0;
>>> +exit:
>>> +	dev_err(&client->dev, "led error %d\n", err);
>>> +
>>> +	while (i--) {
>>> +		if (is31->leds[i].led_cdev.name)
>>> +			led_classdev_unregister(&is31->leds[i].led_cdev);
>>> +	}
>>> +	return err;
>>> +}
>>> +
>>> +static int is31fl319x_remove(struct i2c_client *client)
>>> +{
>>> +	int i;
>>> +	struct is31fl319x_chip *is31 = i2c_get_clientdata(client);
>>> +	struct is31fl319x_led *is31_leds = is31->leds;
>>> +
>>> +	for (i = 0; i < NUM_LEDS; i++) {
>>> +		if (is31_leds[i].led_cdev.name)
>>> +			led_classdev_unregister(&is31_leds[i].led_cdev);
>>> +	}
>>> +
>>> +	cancel_work_sync(&is31->work);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static struct i2c_driver is31fl319x_driver = {
>>> +	.driver   = {
>>> +		.name    = "leds-is31fl319x",
>>> +		.of_match_table = of_match_ptr(of_is31fl319x_leds_match),
>>> +	},
>>> +	.probe    = is31fl319x_probe,
>>> +	.remove   = is31fl319x_remove,
>>> +	.id_table = is31fl319x_id,
>>> +};
>>> +
>>> +module_i2c_driver(is31fl319x_driver);
>>> +
>>> +MODULE_AUTHOR("H. Nikolaus Schaller <hns at goldelico.com>");
>>> +MODULE_DESCRIPTION("IS31FL319X LED driver");
>>> +MODULE_LICENSE("GPL v2");
>>> diff --git a/include/linux/leds-is31fl319x.h b/include/linux/leds-is31fl319x.h
>>> new file mode 100644
>>> index 0000000..5f55abf
>>> --- /dev/null
>>> +++ b/include/linux/leds-is31fl319x.h
>>> @@ -0,0 +1,24 @@
>>> +/*
>>> + * IS31FL3196 LED chip driver.
>>> + *
>>> + * Copyright (C) 2015 H. Nikolaus Schaller <hns at goldelico.com>
>>> + *
>>> + * 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.
>>> + *
>>> + * This program is distributed in the hope that it will be useful, but
>>> + * WITHOUT ANY WARRANTY; without even the implied warranty of
>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>>> + * General Public License for more details.
>>> + */
>>> +
>>> +#ifndef __LINUX_IS31FL319X_H
>>> +#define __LINUX_IS31FL319X_H
>>> +#include <linux/leds.h>
>>> +
>>> +struct is31fl319x_platform_data {
>>> +	struct led_platform_data leds;
>>> +};
>>
>> We don't use led_platform_data for new drivers.
>> Device Tree has become a standard.
>> Effectively this header is not needed, please drop it.
>
> Ok, fine with that!
>
>>
>>> +#endif /* __LINUX_IS31FL319X_H */
>>>
>>
>>
>> --
>> Best regards,
>> Jacek Anaszewski
>
> I will combine all this and resubmit V2 after testing.
>
> BR and thanks,
> Nikolaus
>
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>

-- 
Best regards,
Jacek Anaszewski


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