Re: [PATCH] fastboot: Fix has-slot command always returning yes for fb_nand

[Mattijs Korpershoek <mkorpershoek@kernel.org>]

Hi Chance,

Thank you for the patch.

On Tue, Jul 08, 2025 at 09:16, Chance Yang <chance.yang@kneron.us> wrote:

> The issue was a mismatch in return value conventions between functions:
> - getvar_get_part_info() expects >= 0 for success
> - fb_nand_lookup() returns 0 on success, 1 on failure (from
>   find_dev_and_part)
>
> When partition didn't exist, fb_nand_lookup returned 1, but
> fastboot_nand_get_part_info passed it directly to getvar_get_part_info,
> which treated 1 >= 0 as success, causing has-slot to always return yes.
>
> Fix by converting positive return values to -ENOENT in
> fastboot_nand_get_part_info to match the expected error convention.
>
> Signed-off-by: Chance Yang <chance.yang@kneron.us>
> ---
>  drivers/fastboot/fb_nand.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/fastboot/fb_nand.c b/drivers/fastboot/fb_nand.c
> index afc64fd5280717ae4041ed70268ccc01cfbb0496..b819541eb8fa6f537ca40fb3ea81bc7aab6118bf 100644
> --- a/drivers/fastboot/fb_nand.c
> +++ b/drivers/fastboot/fb_nand.c
> @@ -157,8 +157,13 @@ int fastboot_nand_get_part_info(const char *part_name,
>  				struct part_info **part_info, char *response)
>  {
>  	struct mtd_info *mtd = NULL;
> +	int ret;
> +
> +	ret = fb_nand_lookup(part_name, &mtd, part_info, response);
> +	if (ret > 0)

ret > 0 does not cover all the failure paths in fb_nand_lookup():

Inspecting fb_nand_loopup(), it can fail in 3 different ways.
In case of failure:

1. mtdparts_init(): returns 1
2. find_dev_and_part(): returns 1
3. dev->id->type != MTD_DEV_TYPE_NAND: returns -EINVAL

Right now, we only cover failure path 1. and 2.

Could we change this to:

if (ret)

Thanks,
Mattijs

> +		return -ENOENT;
>  
> -	return fb_nand_lookup(part_name, &mtd, part_info, response);
> +	return ret;
>  }
>  
>  /**
>
> ---
> base-commit: d1d53c252a4a746db5ebcdf0d6de3aa0feec504e
> change-id: 20250708-master-b6a53395df05
>
> Best regards,
> -- 
> Chance Yang <chance.yang@kneron.us>