[PATCH] mmc: sdhci: make tuning_err a signed int

[PATCH] mmc: sdhci: make tuning_err a signed int

[haibo.chen]

From: Haibo Chen <haibo.chen@nxp.com>

Coverity report INTEGER_OVERFLOW for host->tuning_err.
The tuning_err field in struct sdhci_host is used to store an error
code for re-tuning, but it was declared as unsigned int. Several call
sites store negative error codes into it and later compare against
negative values:

  - sdhci.c, sdhci-of-dwcmshc.c and sdhci-pci-gli.c assign it the
    return value of __sdhci_execute_tuning()/__sdhci_execute_tuning_9750(),
    both of which return a signed int (possibly a negative errno);
  - sdhci-of-esdhc.c assigns host->tuning_err = -EAGAIN and later does
    "ret = host->tuning_err; if (ret == -EAGAIN ...)";
  - sdhci-of-dwcmshc.c prints it with the %d (signed) conversion.

Storing a negative errno in an unsigned int and reading it back as a
signed int only happens to work because of two's-complement, same-width
integer conversions. It is misleading and triggers sign-conversion
warnings. All users treat the value either as a signed error code or as
a boolean (zero / non-zero), so changing the type to a signed int is
safe and makes the intent explicit.

Fixes: 7d8bb1f46e13 ("mmc: sdhci: add tuning error codes")
Assisted-by: Cline:claude-sonnet [read_file, search_files, git]
Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
---
 drivers/mmc/host/sdhci.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index b6a571d866fa53ce2aad0105cea2909abe6bce01..f0fd81409a86c6fd9120e69766fa2407c14e9048 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -659,7 +659,7 @@ struct sdhci_host {
 
 	unsigned int		tuning_count;	/* Timer count for re-tuning */
 	unsigned int		tuning_mode;	/* Re-tuning mode supported by host */
-	unsigned int		tuning_err;	/* Error code for re-tuning */
+	int			tuning_err;	/* Error code for re-tuning */
 #define SDHCI_TUNING_MODE_1	0
 #define SDHCI_TUNING_MODE_2	1
 #define SDHCI_TUNING_MODE_3	2

---
base-commit: c5e32e86ca02b003f86e095d379b38148999293d
change-id: 20260727-sdhci-fix-13481630ae02

Best regards,
-- 
Haibo Chen <haibo.chen@nxp.com>

Re: [PATCH] mmc: sdhci: make tuning_err a signed int

[Frank Li]

On Mon, Jul 27, 2026 at 06:38:49PM +0800, haibo.chen@oss.nxp.com wrote:
> From: Haibo Chen <haibo.chen@nxp.com>
>
> Coverity report INTEGER_OVERFLOW for host->tuning_err.
> The tuning_err field in struct sdhci_host is used to store an error
> code for re-tuning, but it was declared as unsigned int. Several call
> sites store negative error codes into it and later compare against
> negative values:
>
>   - sdhci.c, sdhci-of-dwcmshc.c and sdhci-pci-gli.c assign it the
>     return value of __sdhci_execute_tuning()/__sdhci_execute_tuning_9750(),
>     both of which return a signed int (possibly a negative errno);
>   - sdhci-of-esdhc.c assigns host->tuning_err = -EAGAIN and later does
>     "ret = host->tuning_err; if (ret == -EAGAIN ...)";
>   - sdhci-of-dwcmshc.c prints it with the %d (signed) conversion.
>
> Storing a negative errno in an unsigned int and reading it back as a
> signed int only happens to work because of two's-complement, same-width
> integer conversions. It is misleading and triggers sign-conversion
> warnings. All users treat the value either as a signed error code or as
> a boolean (zero / non-zero), so changing the type to a signed int is
> safe and makes the intent explicit.
>
> Fixes: 7d8bb1f46e13 ("mmc: sdhci: add tuning error codes")
> Assisted-by: Cline:claude-sonnet [read_file, search_files, git]
> Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
> ---

Reviewed-by: Frank Li <Frank.Li@nxp.com>

>  drivers/mmc/host/sdhci.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
> index b6a571d866fa53ce2aad0105cea2909abe6bce01..f0fd81409a86c6fd9120e69766fa2407c14e9048 100644
> --- a/drivers/mmc/host/sdhci.h
> +++ b/drivers/mmc/host/sdhci.h
> @@ -659,7 +659,7 @@ struct sdhci_host {
>
>  	unsigned int		tuning_count;	/* Timer count for re-tuning */
>  	unsigned int		tuning_mode;	/* Re-tuning mode supported by host */
> -	unsigned int		tuning_err;	/* Error code for re-tuning */
> +	int			tuning_err;	/* Error code for re-tuning */
>  #define SDHCI_TUNING_MODE_1	0
>  #define SDHCI_TUNING_MODE_2	1
>  #define SDHCI_TUNING_MODE_3	2
>
> ---
> base-commit: c5e32e86ca02b003f86e095d379b38148999293d
> change-id: 20260727-sdhci-fix-13481630ae02
>
> Best regards,
> --
> Haibo Chen <haibo.chen@nxp.com>
>
>