linux-kernel - Re: [PATCH v1 1/1] ACPI: property: Fix return value for nval == 0 in acpi_data_prop

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Message-ID: <CAJZ5v0hr0W+MPFw99-TEf1_Lw6cb2gv3ScL06Jd8rZh06phgow@mail.gmail.com>
Date: Wed, 5 Feb 2025 21:10:56 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org, 
	"Rafael J. Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>
Subject: Re: [PATCH v1 1/1] ACPI: property: Fix return value for nval == 0 in acpi_data_prop_read()

On Mon, Feb 3, 2025 at 8:47 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> While analysing code for software and OF node for the corner case when
> caller asks to read zero items in the supposed to be an array of values
> I found that ACPI behaves differently to what OF does, i.e.
>
> 1. It returns -EINVAL when caller asks to read zero items from integer
> array, while OF returns 0, if no other errors happened.
>
> 2. It returns -EINVAL when caller asks to read zero items from string
> array, while OF returns -ENODATA, if no other errors happened.
>
> Amend ACPI implementation to follow what OF does.
>
> Fixes: b31384fa5de3 ("Driver core: Unified device properties interface for platform firmware")
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  drivers/acpi/property.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/acpi/property.c b/drivers/acpi/property.c
> index 1144c2368d89..7d7f4974c5b1 100644
> --- a/drivers/acpi/property.c
> +++ b/drivers/acpi/property.c
> @@ -1189,8 +1189,6 @@ static int acpi_data_prop_read(const struct acpi_device_data *data,
>                         return -EOVERFLOW;
>                 break;
>         }
> -       if (nval == 0)
> -               return -EINVAL;
>
>         if (obj->type == ACPI_TYPE_BUFFER) {
>                 if (proptype != DEV_PROP_U8)
> @@ -1214,9 +1212,10 @@ static int acpi_data_prop_read(const struct acpi_device_data *data,
>                 ret = acpi_copy_property_array_uint(items, (u64 *)val, nval);
>                 break;
>         case DEV_PROP_STRING:
> -               ret = acpi_copy_property_array_string(
> -                       items, (char **)val,
> -                       min_t(u32, nval, obj->package.count));
> +               nval = min_t(u32, nval, obj->package.count);
> +               if (nval == 0)
> +                       return -ENODATA;
> +               ret = acpi_copy_property_array_string(items, (char **)val, nval);
>                 break;
>         default:
>                 ret = -EINVAL;
> --

Applied as 6.14-rc material, thanks!