Re: [PATCH] leds: add LED driver for CR0014114 board

[Jacek Anaszewski <jacek.anaszewski@gmail.com>]

Hi Oleh,

Thank you for the patch. Please see my comments below.

On 03/12/2018 04:33 PM, Oleh Kravchenko wrote:
> This patch adds a LED class driver for the RGB LEDs found on
> the Crane Merchandising System CR0014114 LEDs board.
> 
> Signed-off-by: Oleh Kravchenko <oleg@kaa.org.ua>
> ---
>  .../devicetree/bindings/leds/leds-cr0014114.txt    |  46 ++++
>  .../devicetree/bindings/vendor-prefixes.txt        |   1 +
>  drivers/leds/Kconfig                               |  13 +
>  drivers/leds/Makefile                              |   1 +
>  drivers/leds/leds-cr0014114.c                      | 282 +++++++++++++++++++++
>  5 files changed, 343 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/leds/leds-cr0014114.txt
>  create mode 100644 drivers/leds/leds-cr0014114.c
> 
> diff --git a/Documentation/devicetree/bindings/leds/leds-cr0014114.txt b/Documentation/devicetree/bindings/leds/leds-cr0014114.txt
> new file mode 100644
> index 000000000000..56721598ee81
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/leds/leds-cr0014114.txt

Please split DT bindings related changes to the separate patch.

> @@ -0,0 +1,46 @@
> +Crane Merchandising System - cr0014114 LED driver
> +-------------------------------------------------
> +
> +This LED Board widely used in vending machines produced
> +by Crane Merchandising Systems.
> +
> +Required properties:
> +- compatible: "cms,cr0014114"

Why here cms and crane in the example below? Please make it
consistent. I assume that vendor prefix should be "crane",
so in this case this should look like below:

- compatible: Must be "crane,cr0014114".

> +- reg: chip select address for the device
> +- spi-cpha: shifted clock phase mode is required

You don't have to say that it is required - it is already
under "Required properties". Apart from that - you don't
parse this property in the driver, so it doesn't seem to
be needed.

> +
> +LED sub-node properties:
> +- label : (optional)
> +	see Documentation/devicetree/bindings/leds/common.txt
> +- linux,default-trigger : (optional)
> +	see Documentation/devicetree/bindings/leds/common.txt
> +
> +Example
> +-------
> +
> +cr0014114@0 {

led-controller@9

> +	compatible = "crane,cr0014114";

You need also below properties to avoid dtc warnings.

#address-cells = <1>;
#size-cells = <0>;


> +	reg = <0>;
> +	spi-max-frequency = <50000>;
> +	spi-cpha;

Please consider if this is really required.

> +	led0 {
> +		label = "cr0:red:";

Please separate "led" from the address with "@" character,
e.g. here it should be led@0.

Also why "cr0" and not full device name "cr0014114"?
You could also think of some exemplary LED functions to not
leave that section empty.


> +	};
> +	led1 {
> +		label = "cr0:green:";
> +	};
> +	led2 {
> +		label = "cr0:blue:";
> +	};
> +	led3 {
> +		label = "cr1:red:";
> +	};
> +	led4 {
> +		label = "cr1:green:";
> +	};
> +	led5 {
> +		label = "cr1:blue:";
> +	};
> +	...
> +};
> diff --git a/Documentation/devicetree/bindings/vendor-prefixes.txt b/Documentation/devicetree/bindings/vendor-prefixes.txt
> index ae850d6c0ad3..f17949c365f5 100644
> --- a/Documentation/devicetree/bindings/vendor-prefixes.txt
> +++ b/Documentation/devicetree/bindings/vendor-prefixes.txt
> @@ -75,6 +75,7 @@ cnxt	Conexant Systems, Inc.
>  compulab	CompuLab Ltd.
>  cortina	Cortina Systems, Inc.
>  cosmic	Cosmic Circuits
> +crane	Crane Connectivity Solutions
>  creative	Creative Technology Ltd
>  crystalfontz	Crystalfontz America, Inc.
>  cubietech	Cubietech, Ltd.
> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
> index 2c896c0e69e1..bb6a70ac5004 100644
> --- a/drivers/leds/Kconfig
> +++ b/drivers/leds/Kconfig
> @@ -104,6 +104,19 @@ config LEDS_CPCAP
>  	  This option enables support for LEDs offered by Motorola's
>  	  CPCAP PMIC.
>  
> +config LEDS_CR0014114
> +	tristate "LED Support for Crane CR0014114"
> +	depends on LEDS_CLASS
> +	depends on SPI
> +	depends on OF
> +	help
> +	  This option enables support for CR0014114 LED Board which
> +	  widely used in vending machines produced by
> +	  Crane Merchandising Systems.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called leds-cr0014114.
> +
>  config LEDS_LM3530
>  	tristate "LCD Backlight driver for LM3530"
>  	depends on LEDS_CLASS
> diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
> index 91eca81cae82..0176e7335994 100644
> --- a/drivers/leds/Makefile
> +++ b/drivers/leds/Makefile
> @@ -78,6 +78,7 @@ obj-$(CONFIG_LEDS_MT6323)		+= leds-mt6323.o
>  obj-$(CONFIG_LEDS_LM3692X)		+= leds-lm3692x.o
>  
>  # LED SPI Drivers
> +obj-$(CONFIG_LEDS_CR0014114)		+= leds-cr0014114.o
>  obj-$(CONFIG_LEDS_DAC124S085)		+= leds-dac124s085.o
>  
>  # LED Userspace Drivers
> diff --git a/drivers/leds/leds-cr0014114.c b/drivers/leds/leds-cr0014114.c
> new file mode 100644
> index 000000000000..e3aecdbea73c
> --- /dev/null
> +++ b/drivers/leds/leds-cr0014114.c
> @@ -0,0 +1,282 @@
> +#include <linux/delay.h>
> +#include <linux/leds.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +#include <linux/property.h>
> +#include <linux/spi/spi.h>
> +#include <linux/spinlock.h>
> +#include <linux/timer.h>
> +#include <linux/workqueue.h>
> +
> +/* CR0014114 SPI commands */
> +#define CR_SET_BRIGHTNESS	0x80
> +#define CR_INIT_REENUMERATE	0x81
> +#define CR_NEXT_REENUMERATE	0x82
> +
> +/* CR0014114 default settings */
> +#define CR_MAX_BRIGHTNESS	GENMASK(6, 0)
> +#define CR_FW_DELAY_MSEC	10
> +#define CR_RECOUNT_DELAY	(HZ * 3600)
> +
> +struct cr0014114_led {
> +	const char		*name;
> +	struct cr0014114	*priv;
> +	struct led_classdev	ldev;
> +	u8			brightness;
> +};
> +
> +struct cr0014114 {
> +	bool			do_recount;
> +	size_t			count;
> +	struct device		*dev;
> +	struct mutex		lock;
> +	struct spi_device	*spi;
> +	struct timer_list	timer;
> +	struct work_struct	work;
> +	unsigned long		delay;
> +	struct cr0014114_led	leds[];
> +};
> +
> +static void cr0014114_calc_crc(u8 *buf, const size_t len)
> +{
> +	size_t	i;
> +	u8	crc;
> +
> +	for (i = 1, crc = 1; i < len - 1; i++)
> +		crc += buf[i];
> +	crc |= BIT(7);
> +
> +	/* special case when CRC matches to SPI commands */
> +	if (crc == CR_SET_BRIGHTNESS ||
> +	    crc == CR_INIT_REENUMERATE ||
> +	    crc == CR_NEXT_REENUMERATE)
> +		crc = 0xfe;
> +
> +	buf[len - 1] = crc;
> +}
> +
> +static int cr0014114_recount(struct cr0014114 *priv)
> +{
> +	int	ret;
> +	size_t	i;
> +	u8	cmd;
> +
> +	dev_dbg(priv->dev, "recount of LEDs is started\n");
> +
> +	do {

This do..while(0) loop isn't really required. Let's do it otherwise.

> +		cmd = CR_INIT_REENUMERATE;
> +		ret = spi_write(priv->spi, &cmd, sizeof(cmd));
> +		if (ret)
> +			break;

Please add a label out_reenum at the end of the function
and goto there from here in case of error.

> +
> +		cmd = CR_NEXT_REENUMERATE;
> +		for (i = 0; i < priv->count; i++) {
> +			msleep(CR_FW_DELAY_MSEC);
> +
> +			ret = spi_write(priv->spi, &cmd, sizeof(cmd));
> +			if (ret)
> +				break;

Similarly goto out_reenum here.

> +		}
> +	} while (0);
> +
> +	dev_dbg(priv->dev, "recount of LEDs is complete, error: %d\n", ret);
> +
> +	return ret;
> +}
> +
> +static int cr0014114_sync(struct cr0014114 *priv)
> +{
> +	int		ret;
> +	size_t		i;
> +	u8		data[priv->count + 2];

sparse is not happy about this and it causes two more problems below:

drivers/leds/leds-cr0014114.c:101:42: warning: Variable length array is
used.
drivers/leds/leds-cr0014114.c:122:42: error: cannot size expression
drivers/leds/leds-cr0014114.c:124:50: error: cannot size expression


> +	unsigned long	udelay, now = jiffies;
> +
> +	/* to avoid SPI mistiming with firmware we should wait some time */
> +	if (time_after(priv->delay, now)) {
> +		udelay = jiffies_to_usecs(priv->delay - now);
> +		usleep_range(udelay, udelay + 1);
> +	}
> +
> +	do {
> +		if (unlikely(priv->do_recount)) {
> +			ret = cr0014114_recount(priv);
> +			if (ret)
> +				break;
> +
> +			priv->do_recount = false;
> +		}
> +
> +		data[0] = CR_SET_BRIGHTNESS;
> +		for (i = 0; i < priv->count; i++)
> +			data[i + 1] = priv->leds[i].brightness;
> +		cr0014114_calc_crc(data, sizeof(data));
> +
> +		ret = spi_write(priv->spi, data, sizeof(data));
> +		if (ret)
> +			break;
> +	} while (0);
> +
> +	priv->delay = jiffies + msecs_to_jiffies(CR_FW_DELAY_MSEC);
> +
> +	return ret;
> +}
> +
> +static void cr0014114_recount_work(struct work_struct *work)
> +{
> +	int			ret;
> +	struct cr0014114	*priv = container_of(work, struct cr0014114,
> +						     work);
> +
> +	mutex_lock(&priv->lock);
> +	priv->do_recount = true;
> +	ret = cr0014114_sync(priv);
> +	mutex_unlock(&priv->lock);
> +
> +	if (ret)
> +		dev_warn(priv->dev, "recount LEDs failed %d\n", ret);
> +}
> +
> +int cr0014114_set_sync(struct led_classdev *ldev,
> +		       enum led_brightness brightness)
> +{
> +	int			ret;
> +	struct cr0014114_led    *led = container_of(ldev,
> +						    struct cr0014114_led,
> +						    ldev);
> +
> +	mutex_lock(&led->priv->lock);
> +	led->brightness = (u8)brightness;
> +	ret = cr0014114_sync(led->priv);
> +	mutex_unlock(&led->priv->lock);
> +
> +	return ret;
> +}
> +
> +void cr0014114_recount_timer(struct timer_list *t)
> +{
> +	struct cr0014114 *priv = from_timer(priv, t, timer);
> +
> +	schedule_work(&priv->work);
> +	mod_timer(&priv->timer, jiffies + CR_RECOUNT_DELAY);
> +}
> +
> +static int cr0014114_probe_dt(struct cr0014114 *priv)
> +{
> +	size_t			i = 0;
> +	struct cr0014114_led	*led;
> +	struct fwnode_handle	*child;
> +	struct device_node	*np;
> +	int			ret;
> +
> +	device_for_each_child_node(priv->dev, child) {
> +		np = to_of_node(child);
> +		led = &priv->leds[i];
> +
> +		ret = fwnode_property_read_string(child, "label",
> +						  &led->name);
> +		if (ret && IS_ENABLED(CONFIG_OF) && np)

The driver already depends on OF, so IS_ENABLED is redundant here.

> +			led->name = np->name;
> +
> +		if (!led->name) {
> +			fwnode_handle_put(child);
> +			return -EINVAL;
> +		}
> +
> +		fwnode_property_read_string(child, "linux,default-trigger",
> +					    &led->ldev.default_trigger);
> +
> +		led->priv			  = priv;
> +		led->ldev.name			  = led->name;
> +		led->ldev.brightness		  = LED_OFF;

This is already secured by kzalloc.

> +		led->ldev.max_brightness	  = CR_MAX_BRIGHTNESS;
> +		led->ldev.brightness_set_blocking = cr0014114_set_sync;
> +
> +		ret = devm_of_led_classdev_register(priv->dev, np,
> +						    &led->ldev);
> +		if (ret) {
> +			fwnode_handle_put(child);
> +			return ret;
> +		}
> +
> +		led->ldev.dev->of_node = np;
> +
> +		i++;
> +	}
> +
> +	return 0;
> +}
> +
> +static int cr0014114_probe(struct spi_device *spi)
> +{
> +	struct cr0014114	*priv;
> +	size_t			count;
> +	int			ret;
> +
> +	count = device_get_child_node_count(&spi->dev);
> +	if (!count) {
> +		dev_err(&spi->dev, "LEDs are not defined in device tree");
> +		return -ENODEV;
> +	}
> +
> +	priv = devm_kzalloc(&spi->dev,
> +			    sizeof(*priv) + sizeof(*priv->leds) * count,
> +			    GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	mutex_init(&priv->lock);
> +	INIT_WORK(&priv->work, cr0014114_recount_work);
> +	priv->do_recount	= true;
> +	priv->count		= count;
> +	priv->dev		= &spi->dev;
> +	priv->spi		= spi;
> +
> +	ret = cr0014114_probe_dt(priv);
> +	if (ret)
> +		return ret;
> +
> +	ret = cr0014114_sync(priv);
> +	if (ret)
> +		return ret;
> +
> +	/* setup recount timer to workaround buggy firmware */
> +	timer_setup(&priv->timer, cr0014114_recount_timer, 0);
> +	mod_timer(&priv->timer, jiffies + CR_RECOUNT_DELAY);
> +
> +	spi_set_drvdata(spi, priv);
> +
> +	return 0;
> +}
> +
> +static int cr0014114_remove(struct spi_device *spi)
> +{
> +	struct cr0014114 *priv = spi_get_drvdata(spi);
> +
> +	cancel_work_sync(&priv->work);
> +	del_timer_sync(&priv->timer);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id cr0014114_dt_ids[] = {
> +	{ .compatible = "crane,cr0014114", },
> +	{},
> +};
> +
> +MODULE_DEVICE_TABLE(of, cr0014114_dt_ids);
> +
> +static struct spi_driver cr0014114_driver = {
> +	.probe		= cr0014114_probe,
> +	.remove		= cr0014114_remove,
> +	.driver = {
> +		.name		= KBUILD_MODNAME,
> +		.of_match_table	= cr0014114_dt_ids,
> +	},
> +};
> +
> +module_spi_driver(cr0014114_driver);
> +
> +MODULE_AUTHOR("Oleh Kravchenko <oleg@kaa.org.ua>");
> +MODULE_DESCRIPTION("cr0014114 LED driver");
> +MODULE_LICENSE("GPL");

Please add SPDX license identifier at the top of the file:
Documentation/process/license-rules.rst

> +MODULE_ALIAS("spi:cr0014114");
> 

-- 
Best regards,
Jacek Anaszewski