linux-kernel - Re: [PATCH V4 04/10] dt-bindings: timestamp: Add nvidia,gpio-controller

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Date:   Tue, 4 Apr 2023 07:33:49 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Dipen Patel <dipenp@...dia.com>, Rob Herring <robh@...nel.org>
Cc:     thierry.reding@...il.com, jonathanh@...dia.com,
        linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-gpio@...r.kernel.org, linus.walleij@...aro.org,
        devicetree@...r.kernel.org, linux-doc@...r.kernel.org,
        timestamp@...ts.linux.dev, krzysztof.kozlowski+dt@...aro.org,
        brgl@...ev.pl, corbet@....net, gregkh@...uxfoundation.org
Subject: Re: [PATCH V4 04/10] dt-bindings: timestamp: Add
 nvidia,gpio-controller

On 04/04/2023 06:24, Dipen Patel wrote:
> On 3/25/23 4:09 AM, Krzysztof Kozlowski wrote:
>> On 24/03/2023 19:51, Dipen Patel wrote:
>>> On 3/24/23 10:13 AM, Rob Herring wrote:
>>>> On Wed, Mar 22, 2023 at 06:29:23PM -0700, Dipen Patel wrote:
>>>>> Introducing nvidia,gpio-controller property from Tegra234 SoCs onwards.
>>>>> This is done to help below case.
>>>>>
>>>>> Without this property code would look like:
>>>>> if (of_device_is_compatible(dev->of_node, "nvidia,tegra194-gte-aon"))
>>>>> 	hte_dev->c = gpiochip_find("tegra194-gpio-aon",
>>>>> 				   tegra_get_gpiochip_from_name);
>>>>> else if (of_device_is_compatible(dev->of_node, "nvidia,tegra234-gte-aon"))
>>>>> 	hte_dev->c = gpiochip_find("tegra234-gpio-aon",
>>>>> 				   tegra_get_gpiochip_from_name);
>>>>> else
>>>>> 	return -ENODEV;
>>>>
>>>> Or you just put the name in match data.
>>>
>>> Not sure I have understood this comment, but "name" the first argument is
>>> already there to supply to callback to match data. Also, this if else is
>>> needed to know which "name" to provide.
>>
>> The point is that of_device_is_compatible() do not really scale and make
>> code more difficult to read. Your variant-customization should in
>> general entirely come from match/driver data.
> 
> Perhaps I should not have mentioned driver related details here about how
> this property will help, that detail will go in driver patch. In the next
> patch series I will remove this commit and just focus on what this property
> is.

Regardless of this commit, driver match data is the way to go, not
of_device_is_compatible().



Best regards,
Krzysztof