From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Rafael J. Wysocki" <rafael@kernel.org>
Subject: Re: [PATCH v3 1/5] ACPI / bus: Return error code from
 __acpi_match_device() in one case
Date: Thu, 8 Feb 2018 16:14:31 +0100
Message-ID: <CAJZ5v0gkn4keNLA4jyCDOjSB4EGhya0d7ecwo-4zDQ=+E9PnJA@mail.gmail.com>
References: <20180207145610.88434-1-andriy.shevchenko@linux.intel.com>
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To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: dmaengine <dmaengine@vger.kernel.org>, "Rafael J . Wysocki" <rjw@rjwysocki.net>, ACPI Devel Maling List <linux-acpi@vger.kernel.org>, Mika Westerberg <mika.westerberg@linux.intel.com>, Sinan Kaya <okaya@codeaurora.org>, Sakari Ailus <sakari.ailus@linux.intel.com>, Vinod Koul <vinod.koul@intel.com>

On Wed, Feb 7, 2018 at 3:56 PM, Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
> Instead of playing tricks with last invalid entry,
> return simple -ENODATA error code cast to pointer.
>
> It would be good for future in case caller passes NULL pointer for
> ID table. Moreover, caller can check the code to be sure what happened
> inside callee.
>
> Fixes: 2b9c698efa58 ("ACPI / scan: Take the PRP0001 position in the list of IDs into account")

I still don't think the Fixes: tag here is valid (the code works as is
AFAICS), but I could drop it when applying the patch just fine. :-)

That said, see below.

> Cc: Sinan Kaya <okaya@codeaurora.org>
> Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
> Cc: Vinod Koul <vinod.koul@intel.com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
>  drivers/acpi/bus.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
> index 58239abb0a72..761286e50067 100644
> --- a/drivers/acpi/bus.c
> +++ b/drivers/acpi/bus.c
> @@ -769,7 +769,7 @@ static const struct acpi_device_id *__acpi_match_device(
>                  */
>                 if (!strcmp(ACPI_DT_NAMESPACE_HID, hwid->id)
>                     && acpi_of_match_device(device, of_ids))
> -                       return id;
> +                       return ERR_PTR(-ENODATA);

Doesn't the comment above need to be updated?

Also the return value here means "success", so why is an error the right choice?

>         }
>         return NULL;
>  }
> --

Overall, this really looks like a preparation for a future patch, so
why not just say that straight away in the changelog?