Message-Id: <80A3B3D8-2309-4A41-91F9-4A2EE6DDF975@goldelico.com>
Date:	Tue, 19 Apr 2016 19:21:05 +0200
From:	"H. Nikolaus Schaller" <hns@...delico.com>
To:	"David Rivshin (Allworx)" <drivshin.allworx@...il.com>
Cc:	Rob Herring <robh+dt@...nel.org>, Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Richard Purdie <rpurdie@...ys.net>,
	Jacek Anaszewski <j.anaszewski@...sung.com>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-leds@...r.kernel.org, kernel@...a-handheld.com,
	marek@...delico.com, letux-kernel@...nphoenux.org
Subject: Re: [PATCH] drivers: led: is31fl319x: 6/9-channel light effect led driver

Hi David,


> Am 19.04.2016 um 03:25 schrieb David Rivshin (Allworx) <drivshin.allworx@...il.com>:
> 
> Hi Nikolaus,
> 
> I recently submitted a driver for the IS31FL32xx family of devices, so
> this driver caught my eye. I have a few comments below.
> 
> On Mon, 18 Apr 2016 20:43:16 +0200
> "H. Nikolaus Schaller" <hns@...delico.com> 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@...delico.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".
> 
> From a quick look at the datasheets, I believe the Si-En SN3199 [1] 
> is the same as the ISSI IS31FL3199. ISSI purchased Si-En in 2011,
> and looks to have rebranded Si-En's existing LED controllers. 
> Assuming the SN3199 is indeed the same as the IS31FL3199, I would
> suggest adding a compatible string of "si-en,sn3199" both here
> and in the driver itself (and update the Kconfig text as well). 
> 
> [1] http://www.si-en.com/product.asp?parentid=890

Sounds reasonable. Added.

> 
>> +- #address-cells: must be 1
>> +- #size-cells: must be 0
>> +- reg: 0x64, 0x65, 0x66, 0x67.
>> +
>> +Optional properties:
>> +- max-current-ma:	maximum led current (5..40 mA, default 20 mA)
>> +- audio-gain-db:	audio gain selection (0..21 dB. default 0 dB)
>> +- breathing & audio:	not implemented
> 
> I'm not certain, but that last line feels wrong to me. I would expect
> to see just defined properties in this section, while that is more
> commentary. I would just leave it out, myself.

Yes, you are right. We had planned to add something and written the bindings
document first but never implemented it (because we don't need it any more).

> 
>> +
>> +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)
> 
> Since the datasheets for these devices name the outputs "OUT1" through 
> "OUT6"/"OUT9", I believe the correct range for the 'reg' property should 
> be 1-6 and 1-9. At least that was the result of a discussion with Rob
> Herring [2], and therefore how the IS31FL32xx binding/driver was done.
> It also makes devicetrees easier to write relative to schematics which 
> likely use the OUT1-N naming.
> 
> [2] http://www.spinics.net/lists/devicetree/msg116019.html

Ok, done.

> 
> 
>> +- linux,default-trigger : (optional)
>> +   see Documentation/devicetree/bindings/leds/common.txt
>> +
>> +Examples:
>> +
>> +fancy_leds: is31fl3196@65 {
> 
> I believe the current preference would be to name the node by
> its function, rather than the device. For example:
> 	fancy_leds: leds@65

Updated.

> 
>> +	compatible = "issi,is31fl319x";
> 
> I believe this should be "issi,is31fl3196" here.

Indeed.

> 
>> +	#address-cells = <1>;
>> +	#size-cells = <0>;
>> +	reg = <0x65>;
>> +
>> +	led0: red-aux@0 {
>> +		label = "red:aux";
>> +		reg = <0>;
>> +	};
>> +
>> +	led1: green-power@4 {
>> +		label = "green:power";
>> +		reg = <4>;
>> +		linux,default-trigger = "default-on";
>> +	};
>> +};
>> +
>> 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"
> 
> Pedantic: "chips" (plural) seems appropriate here.

:)

> 
>> +	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.
> 
> Pedantic: "supports" seems appropriate here.

Ok.

> 
> I don't think this matters much, but I'm curious: any reason why this entry
> is inserted in the middle of the list, rather than at the end?

Hm. Probably by accident. We were working on it for a while and maybe
appended it somewhere reasonable and rebasing has moved it around.

> Or better, 
> right before/after the IS31FL32XX entry?

Ah, we were not aware that it exists. It appeared some weeks ago, right?

Yes, that would be the logical position and IMHO before the FL32.

I have also harmonized the config help with the is21fl32.

> 
>> +
>> 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-$(CONFIG_LEDS_IS31FL319X)		+= leds-is31fl319x.o
> 
> Ditto.
> 
>> obj-$(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@...delico.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.
> 
> I see that there are also 3190, 3191, and 3193 devices. Is it reasonable
> to think that support for those devices could be added to this driver
> in the future? I'm merely thinking of it from the POV that it is named
> is31fl319x.c. 

I wasn't even aware of the 0/1/3 variants. I have checked with the data
sheet and could not find any significant difference except the number
of outputs and which output pads are available.

Since there isn't even any difference between the 3190 and 3191 except
the date of publication, I assume it is all the same silion die selected after
testing. So they package those with broken outputs 7-9 as 3196, with
broken outputs 4-6 as 3193 etc. Would be very reasonable from a
commecial/chip production point of view.

So I have added all of them to the compatible strings. Since the driver
already dynamically takes care of the number of leds it should simply
work.

> 
>> + *
>> + */
>> +
>> +#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>
>> +
>> +/* 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];
> 
> I would suggest using the regmap infrastructure if you need
> to cache the register values. It also helpfully exports a
> debugfs interface.

There was an issue with regmap I don't exactly remember.

Maybe it was because it is impossible to read (initial) values from the
chip. Only write new ones. And check for chip presence can also only be
done by checking if it responds or fails to a write command. So we would
have to use tricks to make regmap work as intended.

And it may introduce overhead in initialization and does
not save memory.

> 
>> +
>> +	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 },

^^^there is also a bug using is31fl3196 twice

>> +	{ }
>> +};
>> +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);
> 
> I believe the LEDS core now handles the workqueues generically for 
> blocking operations, so it's no longer needed in the individual drivers.

We had a lot of trouble with locking and blocking especially if we
want to indicate CPU or (root) disk activity.

So it is implemented in a way that changes can be requested faster
than the I2C bus can write new values to the chip.

Only after one sequence of I2C writes is done, another work function
can be scheduled. And each group of writes updates as many LEDs
in parallel if necessary.

> 
>> +
>> +	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;
>> +		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 */
>> +	}
> 
> Is any locking needed while iterating over is31->leds[]? Is there any
> opportunity for a race? 

No, because our locking mechanism ensures that only one work function
is running at a time.

Yes there is a small race if a brightness value is updated by an interrupt.

But since the worker is already running, another one will be scheduled that
will fix the value. So for an invisibly short moment there might be the wrong value.

> 
>> +
>> +	/* 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));
>> +}
> 
> I believe that the LEDS core remembers the last set brightness for each LED,
> and will use it if no brightness_get function is implemented. Since all is31fl319x_brightness_get() does is retrieve the saved value from your cache, 
> I think you can just eliminate is31fl319x_brightness_get() altogether.

Well, we do not use it as a real getter because as you say the LEDS core remembers
it.

But we call it in the setter to determine if there is a change.

> 
>> +
>> +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)) {

Here.

Maybe we could inline the call to is31fl319x_read() and even inline
is31fl319x_read because that is also the only location where it is used.

But it removes some inherent layering of the code (lowest level = read/write
chip, get = know which registers to read, set = schedule work only if needed).

I have left it as is for the next version. Let's see if there are more comments.

>> +		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;
> 
> The Kconfig entry claims hardware blink support. The comment here
> says the opposite. I believe this current implementation will result
> in the LEDS core falling back to software blink, but the same result
> would be achieved by just not setting the blink_set callback.
> 

Yes, you are right. We wanted to implement HW blinking later.
So let's remove it here and from Kconfig.

>> +}
>> +
>> +#ifdef CONFIG_OF
>> +static struct is31fl319x_platform_data *
>> +is31fl319x_led_dt_init(struct i2c_client *client, int num_leds)
>> +{
>> +	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);
> 
> I believe it is better to use of_property_read_string() for these.

Sounds good, because it does some error checks but makes error handling
a little more complex (since it is an optional property).

> 
>> +		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);
> 
> There are two errors (invalid DT) detected here, but the driver continues
> to load. I believe the preference is for errors like this to result in the 
> probe failing outright.

I regard this type of error as a flaw that does not require the driver to probe completely.
It simply uses the last of the duplicate definitions. By looking into the kernel log
the error in DT can be easily seen and fixed (instead of wondering why all LEDs
remain off).

> 
> 
>> +		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);
>> +
>> +	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",
>> +				(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) */
>> +	}
>> +
>> +	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;
> 
> I don't see led_cdev.brightness_get being set here. Although if you do 
> remove is31fl319x_brightness_get(), it obviously won't need to be set.

Well, it is used in our is31fl319x_brightness_set function so we can't
remove it completely.

> 
>> +			err = led_classdev_register(&client->dev,
>> +						    &l->led_cdev);
> 
> I would suggest using devm_led_classdev_register(). Then you can remove
> all the calls to led_classdev_unregister() in error and cleanup paths.

Ok.

> 
>> +			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);
>> +	}
>> +
>> +	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@...delico.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@...delico.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;
>> +};
>> +
>> +#endif /* __LINUX_IS31FL319X_H */
> 

In the next days I will debug and test the fixes...

BR and thanks,
Nikolaus

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