Message-ID: <20160303194531.316d7918.drivshin.allworx@gmail.com>
Date:	Thu, 3 Mar 2016 19:45:31 -0500
From:	"David Rivshin (Allworx)" <drivshin.allworx@...il.com>
To:	Jacek Anaszewski <j.anaszewski@...sung.com>
Cc:	linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
	Richard Purdie <rpurdie@...ys.net>,
	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>,
	Stefan Wahren <stefan.wahren@...e.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] leds: Add driver for the ISSI IS31FL32xx family of
 LED controllers

On Thu, 03 Mar 2016 15:51:32 +0100
Jacek Anaszewski <j.anaszewski@...sung.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@...worx.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@...worx.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.

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?

> > +	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@...worx.com>");
> > +MODULE_DESCRIPTION("ISSI IS31FL32xx LED driver");
> > +MODULE_LICENSE("GPL v2");
> >  

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