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Date: Wed, 12 Apr 2023 14:30:04 +0530
From: Naresh Solanki <naresh.solanki@...ements.com>
To: Lee Jones <lee@...nel.org>
Cc: Pavel Machek <pavel@....cz>,
Patrick Rudolph <patrick.rudolph@...ements.com>,
linux-kernel@...r.kernel.org, linux-leds@...r.kernel.org
Subject: Re: [PATCH v3 2/2] leds: max597x: Add support for max597x
Hi Lee,
On 05-04-2023 08:37 pm, Lee Jones wrote:
> On Tue, 28 Mar 2023, Naresh Solanki wrote:
>
>> From: Patrick Rudolph <patrick.rudolph@...ements.com>
>>
>> max597x is hot swap controller with indicator LED support.
>> This driver uses DT property to configure led during boot time &
>> also provide the LED control in sysfs.
>>
>> DTS example:
>> i2c {
>> #address-cells = <1>;
>> #size-cells = <0>;
>> regulator@3a {
>> compatible = "maxim,max5978";
>> reg = <0x3a>;
>> vss1-supply = <&p3v3>;
>>
>> regulators {
>> sw0_ref_0: sw0 {
>> shunt-resistor-micro-ohms = <12000>;
>> };
>> };
>>
>> leds {
>> #address-cells = <1>;
>> #size-cells = <0>;
>> led@0 {
>> reg = <0>;
>> label = "led0";
>> default-state = "on";
>> };
>> led@1 {
>> reg = <1>;
>> label = "led1";
>> default-state = "on";
>> };
>> };
>> };
>> };
>>
>> Signed-off-by: Patrick Rudolph <patrick.rudolph@...ements.com>
>> Signed-off-by: Naresh Solanki <Naresh.Solanki@...ements.com>
>> ...
>> Changes in V3:
>> - Remove of_node_put as its handled by for loop
>> - Print error if an LED fails to register.
>> - Update driver name in Kconfig description
>> - Remove unneeded variable assignment
>> - Use devm_led_classdev_register to reget led
>> Changes in V2:
>> - Fix regmap update
>> - Remove devm_kfree
>> - Remove default-state
>> - Add example dts in commit message
>> - Fix whitespace in Kconfig
>> - Fix comment
>> ---
>> drivers/leds/Kconfig | 11 ++++
>> drivers/leds/Makefile | 1 +
>> drivers/leds/leds-max597x.c | 112 ++++++++++++++++++++++++++++++++++++
>> 3 files changed, 124 insertions(+)
>> create mode 100644 drivers/leds/leds-max597x.c
>>
>> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
>> index 9dbce09eabac..60004cb8c257 100644
>> --- a/drivers/leds/Kconfig
>> +++ b/drivers/leds/Kconfig
>> @@ -590,6 +590,17 @@ config LEDS_ADP5520
>> To compile this driver as a module, choose M here: the module will
>> be called leds-adp5520.
>>
>> +config LEDS_MAX597X
>> + tristate "LED Support for Maxim 597x"
>> + depends on LEDS_CLASS
>> + depends on MFD_MAX597X
>> + help
>> + This option enables support for the Maxim MAX5970 & MAX5978 smart
>> + switch indication LEDs via the I2C bus.
>> +
>> + To compile this driver as a module, choose M here: the module will
>> + be called leds-max597x.
>> +
>> config LEDS_MC13783
>> tristate "LED Support for MC13XXX PMIC"
>> depends on LEDS_CLASS
>> diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
>> index d30395d11fd8..da1192e40268 100644
>> --- a/drivers/leds/Makefile
>> +++ b/drivers/leds/Makefile
>> @@ -53,6 +53,7 @@ obj-$(CONFIG_LEDS_LP8501) += leds-lp8501.o
>> obj-$(CONFIG_LEDS_LP8788) += leds-lp8788.o
>> obj-$(CONFIG_LEDS_LP8860) += leds-lp8860.o
>> obj-$(CONFIG_LEDS_LT3593) += leds-lt3593.o
>> +obj-$(CONFIG_LEDS_MAX597X) += leds-max597x.o
>> obj-$(CONFIG_LEDS_MAX77650) += leds-max77650.o
>> obj-$(CONFIG_LEDS_MAX8997) += leds-max8997.o
>> obj-$(CONFIG_LEDS_MC13783) += leds-mc13783.o
>> diff --git a/drivers/leds/leds-max597x.c b/drivers/leds/leds-max597x.c
>> new file mode 100644
>> index 000000000000..83e4dfb617fb
>> --- /dev/null
>> +++ b/drivers/leds/leds-max597x.c
>> @@ -0,0 +1,112 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Device driver for leds in MAX5970 and MAX5978 IC
>> + *
>> + * Copyright (c) 2022 9elements GmbH
>> + *
>> + * Author: Patrick Rudolph <patrick.rudolph@...ements.com>
>> + */
>> +
>> +#include <linux/leds.h>
>> +#include <linux/mfd/max597x.h>
>> +#include <linux/of.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/regmap.h>
>> +
>> +#define ldev_to_maxled(c) container_of(c, struct max597x_led, led)
>> +
>> +struct max597x_led {
>> + struct regmap *regmap;
>> + struct led_classdev led;
>> + unsigned int index;
>> +};
>> +
>> +static int max597x_led_set_brightness(struct led_classdev *cdev,
>> + enum led_brightness brightness)
>> +{
>> + struct max597x_led *led = ldev_to_maxled(cdev);
>> + int ret, val = 0;
>
> Why preinitialise?
Ack. Not needed so will remove.
>
>> + if (!led || !led->regmap)
>> + return -ENODEV;
>
> Can !led actually happen?
Ack. Will remove !led .
>
>> + val = !brightness ? BIT(led->index) : 0;
>
> Perhaps a comment?
Sure. Will add "Set/Clear Led index bit"
>
>> + ret = regmap_update_bits(led->regmap, MAX5970_REG_LED_FLASH, BIT(led->index), val);
>> + if (ret < 0)
>> + dev_err(cdev->dev, "failed to set brightness %d\n", ret);
>
> '\n'
Ack
>
>> + return ret;
>> +}
>> +
>> +static int max597x_setup_led(struct device *dev, struct regmap *regmap, struct device_node *nc,
>> + u32 reg)
>> +{
>> + struct max597x_led *led;
>> + int ret;
>> +
>> + led = devm_kzalloc(dev, sizeof(struct max597x_led),
>> + GFP_KERNEL);
>
> Consistently break at 100-chars please.
>
> You have lines wayyyy longer than this elsewhere.
Ack. Will align with 100-chars. Thanks
>
>> + if (!led)
>
> 'led' is confusing. Either this or the member 'led' should be changed.
>
> Perhaps ddata here and cdev for the member?
Sure.
>
>> + return -ENOMEM;
>> +
>> + if (of_property_read_string(nc, "label", &led->led.name))
>> + led->led.name = nc->name;
>> +
>> + led->led.max_brightness = 1;
>> + led->led.brightness_set_blocking = max597x_led_set_brightness;
>> + led->led.default_trigger = "none";
>> + led->index = reg;
>> + led->regmap = regmap;
>> + ret = devm_led_classdev_register(dev, &led->led);
>> + if (ret)
>> + dev_err(dev, "Error in initializing led %s", led->led.name);
>
> Drop the "in" and s/led/LED/
Ack
>
>> +
>> + return ret;
>> +}
>> +
>> +static int max597x_led_probe(struct platform_device *pdev)
>> +{
>> + struct device_node *np = dev_of_node(pdev->dev.parent);
>
> Why not have your own compatible string?
This is leaf driver & MFD driver does has compatible string.
>
>> + struct regmap *regmap = dev_get_regmap(pdev->dev.parent, NULL);
>
> These "big" API calls are usually done outside of the allocation block.
>
> Please move it to just above the check for !regmap.
>
>> + struct device_node *led_node;
>> + struct device_node *child;
>> + int ret = 0;
>
> Is it okay for an LED driver to not to register any LEDs?
Yes. Usage of indication LED on the max5970/5978 is optional.
>
> Perhaps -ENODEV?
This driver is loaded only if MFD driver is included. remap is setup by
MFD driver & hence defer probe till MFD driver is loaded.
>
>> + if (!regmap)
>> + return -EPROBE_DEFER;
>> +
>> + led_node = of_get_child_by_name(np, "leds");
>> + if (!led_node)
>> + return -ENODEV;
>
> Ah, that's better. So set ret to -ENODEV and use it here.
Yes.
>
>> + for_each_available_child_of_node(led_node, child) {
>> + u32 reg;
>> +
>> + if (of_property_read_u32(child, "reg", ®))
>> + continue;
>> +
>> + if (reg >= MAX597X_NUM_LEDS) {
>> + dev_err(&pdev->dev, "invalid LED (%u >= %d)\n", reg,
>> + MAX597X_NUM_LEDS);
>> + continue;
>> + }
>> +
>> + ret = max597x_setup_led(&pdev->dev, regmap, child, reg);
>> + if (ret < 0)
>> + dev_err(&pdev->dev, "Failed to initialize LED %u\n", reg);
>
> I think you (or I) are missing the point of the previous reviews. It's
> not okay to error out and continue executing. Either this is okay (you
> can warn and carry on) or it's not (return an error). Your first
> submission suggested that this was an error. In which case you do need
> to return. I think Pavel was suggesting that you should unwind
> (de-register) before retuning, rather than leaving things in an odd
> half-registered state. Not that you should blindly carry on as if the
> issue never occurred.
I did refer to other such implementations & some have used return on
error & some just print on error & continue. I felt that continue
executing with warning(on error) is better approach.
>
>> + }
>> +
>> + return ret;
>> +}
>> +
>> +static struct platform_driver max597x_led_driver = {
>> + .driver = {
>> + .name = "max597x-led",
>> + },
>> + .probe = max597x_led_probe,
>> +};
>> +
>
> Remove this line.
>> +module_platform_driver(max597x_led_driver);
>> +
>> +MODULE_AUTHOR("Patrick Rudolph <patrick.rudolph@...ements.com>");
>> +MODULE_DESCRIPTION("MAX5970_hot-swap controller driver");
>
> Odd. I thought this was a LED driver?
This also has LED. will update the strign to:
MAX5970_hot-swap controller LED driver
>
>> +MODULE_LICENSE("GPL");
>> --
>> 2.39.1
>>
>
> --
> Lee Jones [李琼斯]
Regards,
Naresh
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