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SubjectRe: [PATCH v4 7/9] watchdog: max77620: add support for the max77714 variant
Date
On 11/29/21 1:24 PM, Luca Ceresoli wrote:
[ ... ]
>>>
>>> +static const struct max77620_variant max77620_wdt_data = {
>>> + .wdt_info = {
>>> + .identity = "max77620-watchdog",
>>> + .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
>>> + },
>>
>> That does not have to be, and should not be, part of device specific data,
>> just because of the identity string.
>
> Ok, no problem, will fix, but I have two questions.
>
> First, what's the reason? Coding style or a functional difference?
> Usually const data is preferred to runtime assignment.
>

wdt_info is not chip specific variant information as nothing but the identity
string is different, and there is no technical need for that difference.

> Second: it's not clear how you expect it to be done. Looking into the

I gave you three options to pick from.

> kernel it looks like almost all drivers set a constant string. I could
> find only one exception, f71808e_wdt:
> https://elixir.bootlin.com/linux/v5.16-rc3/source/drivers/watchdog/f71808e_wdt.c#L471
>
>> Either keep the current identity string,
>> mark max77620_wdt_info as __ro_after_init and overwrite the identity string
>> there during probe
>
> And also remove 'static' I guess. Hm, I don't love this, as above I tend
> to prefer static const when possible for file-scoped data.
>

Where did I suggest to remove 'static', and what would be the benefit of making
the variable global ?

>> or add the structure to max77620_wdt and fill it out there.
>
> Do you mean like the following, untested, kind-of-pseudocode?
>
> struct max77620_wdt {
> struct device *dev;
> struct regmap *rmap;
> const struct max77620_variant *drv_data;
> + struct watchdog_info info; /* not a pointer! */
> struct watchdog_device wdt_dev;
> };
>
> and then, in probe:
>
> wdt->dev = dev;
> wdt->drv_data = (const struct max77620_variant *)id->driver_data;
> /* ... assign other wdt fields ... */
> + strlcpy(wdt_dev->info.identity, id->name, \
> + sizeof(wdt_dev->info.identity));
> + wdt_dev->info.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | \
> + WDIOF_MAGICCLOSE;
>
For example, yes.

> Finally, what about simply:
>
> static const struct max77620_variant max77620_wdt_data = {
> .wdt_info = {
> - .identity = "max77620-watchdog",
> + .identity = "max77xxx-watchdog",
> .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | ...
> },
>
> and always use that struct unconditionally? The max63xx_wdt.c driver
> seems to do that. Or, if this is an issue for backward compatibility (is
> it?), just leave max77620_wdt_data and the .identity field will always
> be "max77620-watchdog" even when using a MAX77714.

Also ok with me.

Guenter

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