linux-kernel - Re: [PATCH] mfd: madera: work around false-positive -Wininitialized warning

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Message-ID: <1e7d772f-f4db-4202-a9c5-6792b37c3d26@opensource.cirrus.com>
Date: Thu, 7 Aug 2025 14:15:35 +0100
From: Richard Fitzgerald <rf@...nsource.cirrus.com>
To: Arnd Bergmann <arnd@...nel.org>,
        Charles Keepax <ckeepax@...nsource.cirrus.com>,
        Lee Jones <lee@...nel.org>, Nathan Chancellor <nathan@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>,
        Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
        Bill Wendling <morbo@...gle.com>,
        Justin Stitt <justinstitt@...gle.com>, linux-sound@...r.kernel.org,
        patches@...nsource.cirrus.com, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev
Subject: Re: [PATCH] mfd: madera: work around false-positive -Wininitialized
 warning

On 07/08/2025 8:19 am, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> clang-21 warns about one uninitialized variable getting dereferenced
> in madera_dev_init:
> 
> drivers/mfd/madera-core.c:739:10: error: variable 'mfd_devs' is uninitialized when used here [-Werror,-Wuninitialized]
>    739 |                               mfd_devs, n_devs,
>        |                               ^~~~~~~~
> drivers/mfd/madera-core.c:459:33: note: initialize the variable 'mfd_devs' to silence this warning
>    459 |         const struct mfd_cell *mfd_devs;
>        |                                        ^
>        |                                         = NULL
> 
> The code is actually correct here because n_devs is only nonzero
> when mfd_devs is a valid pointer, but this is impossible for the
> compiler to see reliably.
> 
> Change the logic to check for the pointer as well, to make this easier
> for the compiler to follow.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>   drivers/mfd/madera-core.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mfd/madera-core.c b/drivers/mfd/madera-core.c
> index bdbd5bfc9714..2f74a8c644a3 100644
> --- a/drivers/mfd/madera-core.c
> +++ b/drivers/mfd/madera-core.c
> @@ -456,7 +456,7 @@ int madera_dev_init(struct madera *madera)
>   	struct device *dev = madera->dev;
>   	unsigned int hwid;
>   	int (*patch_fn)(struct madera *) = NULL;
> -	const struct mfd_cell *mfd_devs;
> +	const struct mfd_cell *mfd_devs = NULL;
>   	int n_devs = 0;
>   	int i, ret;
>   
> @@ -670,7 +670,7 @@ int madera_dev_init(struct madera *madera)
>   		goto err_reset;
>   	}
>   
> -	if (!n_devs) {
> +	if (!n_devs || !mfd_devs) {
>   		dev_err(madera->dev, "Device ID 0x%x not a %s\n", hwid,
>   			madera->type_name);
>   		ret = -ENODEV;
Reviewed-by: Richard Fitzgerald <rf@...nsource.cirrus.com>