linux-kernel - Re: [PATCH v1 01/21] hwmon: Fix the type of 'config' in struct hwmon_channel

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Message-ID: <Z4_T3s7zn3UQNkbW@shell.armlinux.org.uk>
Date: Tue, 21 Jan 2025 17:05:34 +0000
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Huisong Li <lihuisong@...wei.com>
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Subject: Re: [PATCH v1 01/21] hwmon: Fix the type of 'config' in struct
 hwmon_channel_info to u64

On Tue, Jan 21, 2025 at 02:44:59PM +0800, Huisong Li wrote:
>   */
>  struct hwmon_channel_info {
>  	enum hwmon_sensor_types type;
> -	const u32 *config;
> +	const u64 *config;
>  };
>  
>  #define HWMON_CHANNEL_INFO(stype, ...)		\
>  	(&(const struct hwmon_channel_info) {	\
>  		.type = hwmon_##stype,		\
> -		.config = (const u32 []) {	\
> +		.config = (const u64 []) {	\
>  			__VA_ARGS__, 0		\
>  		}				\
>  	})

I'm sorry, but... no. Just no. Have you tried building with only your
first patch?

It will cause the compiler to barf on, e.g. the following:

static u32 marvell_hwmon_chip_config[] = {
...

static const struct hwmon_channel_info marvell_hwmon_chip = {
        .type = hwmon_chip,
        .config = marvell_hwmon_chip_config,
};

I suggest that you rearrange your series: first, do the conversions
to HWMON_CHANNEL_INFO() in the drivers you have.

At this point, if all the drivers that assign to hw_channel_info.config
have been converted, this patch 1 is then suitable.

If there are still drivers that assign a u32 array to
hw_channel_info.config, then you need to consider how to handle
that without causing regressions. You can't cast it between a u32
array and u64 array to silence the warning, because config[1]
won't point at the next entry.

I think your only option would be to combine the conversion of struct
hwmon_channel_info and the other drivers into a single patch. Slightly
annoying, but without introducing more preprocessor yuckiness, I don't
see another way.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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