linux-kernel - Re: [PATCH v5] leds: max597x: Add support for max597x

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Message-ID: <03f1691e-bdc2-90cc-4014-585703d2cf4e@9elements.com>
Date:   Mon, 24 Apr 2023 15:10:08 +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 v5] leds: max597x: Add support for max597x

Hi,

On 21-04-2023 12:49 pm, Lee Jones wrote:
> On Thu, 20 Apr 2023, Naresh Solanki wrote:
> 
>> Hi Lee,
>>
>> On 20-04-2023 07:24 pm, Lee Jones wrote:
>>> On Thu, 20 Apr 2023, Naresh Solanki wrote:
>>>
>>>> Hi Lee,
>>>>
>>>> On 20-04-2023 05:20 pm, Lee Jones wrote:
>>>>> On Mon, 17 Apr 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 = "ssd0:green";
>>>>>>                        default-state = "on";
>>>>>>                    };
>>>>>>                    led@1 {
>>>>>>                        reg = <1>;
>>>>>>                        label = "ssd1:green";
>>>>>>                        default-state = "on";
>>>>>>                    };
>>>>>>                };
>>>>>>            };
>>>>>>        };
>>>>>
>>>>> Where is the DT binding document for this?
>> https://git.kernel.org/pub/scm/linux/kernel/git/lee/mfd.git/tree/Documentation/devicetree/bindings/mfd/maxim,max5970.yaml?h=for-mfd-next
> 
> You need to update it.  It is different to the one you supplied here.
Ack.
> 
>>>>>> Signed-off-by: Patrick Rudolph <patrick.rudolph@...ements.com>
>>>>>> Signed-off-by: Naresh Solanki <Naresh.Solanki@...ements.com>
>>>>>> ...
>>>>>> Changes in V5:
>>>>>> - Update commit message
>>>>>> - Fix comments
>>>>>> - Add necessary new line
>>>>>> Changes in V4:
>>>>>> - Remove unwanted preinitialise
>>>>>> - Remove unneeded line breaks
>>>>>> - Fix variable name to avoid confusion
>>>>>> - Update module description to mention LED driver.
>>>>>> 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 | 115 ++++++++++++++++++++++++++++++++++++
>>>>>>     3 files changed, 127 insertions(+)
>>>>>>     create mode 100644 drivers/leds/leds-max597x.c
> 
> [...]
> 
>>>>> +	led_node = of_get_child_by_name(np, "leds");
>>>>>> +	if (!led_node)
>>>>>> +		return -ENODEV;
>>>
>>> It's odd for a device to be referring to itself as the "child".
>> As this is leaf driver, LED specific info is present in "leds" node in DT.
> 
> I'm aware of the architecture.
> 
> If you give the LEDs driver it's own compatible you don't need to keep
> doing this self->parent->child level-jumping craziness to obtain
> resources.
 From my understanding, it is preferable to have only one compatible per 
chip(in this case MFD driver), and the leaf driver can leverage it 
unless it is not serving the purpose/breaks something.
I think this is acceptable as long as it doesn't creates any 
issue/breaks anything.
> 


Regards,
Naresh