linux-kernel - Re: [PATCH] dmi: Make dmi_walk and dmi_walk

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Date:   Thu, 1 Jun 2017 10:05:43 +0200
From:   Jean Delvare <jdelvare@...e.de>
To:     Darren Hart <dvhart@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Jean Delvare <jdelvare@...e.com>
Subject: Re: [PATCH] dmi: Make dmi_walk and dmi_walk_early return real error
 codes

Hi Darren,

On Fri, 26 May 2017 16:59:17 -0700, Darren Hart wrote:
> From: Andy Lutomirski <luto@...nel.org>
> 
> Currently they return -1 on error, which will confuse callers if
> they try to interpret it as a normal negative error code.

I thought would had fixed this already, but apparently not.

> Signed-off-by: Andy Lutomirski <luto@...nel.org>
> Cc: Jean Delvare <jdelvare@...e.com>
> Signed-off-by: Darren Hart (VMware) <dvhart@...radead.org>
> ---
>  drivers/firmware/dmi_scan.c | 9 +++++----
>  include/linux/dmi.h         | 2 +-
>  2 files changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
> index 54be60e..08b3c8b 100644
> --- a/drivers/firmware/dmi_scan.c
> +++ b/drivers/firmware/dmi_scan.c
> @@ -144,7 +144,7 @@ static int __init dmi_walk_early(void (*decode)(const struct dmi_header *,
>  
>  	buf = dmi_early_remap(dmi_base, orig_dmi_len);
>  	if (buf == NULL)
> -		return -1;
> +		return -ENOMEM;
>  
>  	dmi_decode_table(buf, decode, NULL);
>  
> @@ -992,7 +992,8 @@ EXPORT_SYMBOL(dmi_get_date);
>   *	@decode: Callback function
>   *	@private_data: Private data to be passed to the callback function
>   *
> - *	Returns -1 when the DMI table can't be reached, 0 on success.
> + *	Returns 0 on success, -ENXIO if DMI is not selected or not present,
> + *	or a different negative error code if DMI walking fails.

You document this...

>   */
>  int dmi_walk(void (*decode)(const struct dmi_header *, void *),
>  	     void *private_data)
> @@ -1000,11 +1001,11 @@ int dmi_walk(void (*decode)(const struct dmi_header *, void *),
>  	u8 *buf;
>  
>  	if (!dmi_available)
> -		return -1;
> +		return -ENOENT;

... but implementation differs? I think you should return -ENXIO here,
as when DMI support isn't included. I can't think of a reason why the
caller would treat both cases differently.

>  
>  	buf = dmi_remap(dmi_base, dmi_len);
>  	if (buf == NULL)
> -		return -1;
> +		return -ENOMEM;
>  
>  	dmi_decode_table(buf, decode, private_data);
>  
> diff --git a/include/linux/dmi.h b/include/linux/dmi.h
> index 5e9c74c..9bbf21a 100644
> --- a/include/linux/dmi.h
> +++ b/include/linux/dmi.h
> @@ -136,7 +136,7 @@ static inline int dmi_name_in_vendors(const char *s) { return 0; }
>  static inline int dmi_name_in_serial(const char *s) { return 0; }
>  #define dmi_available 0
>  static inline int dmi_walk(void (*decode)(const struct dmi_header *, void *),
> -	void *private_data) { return -1; }
> +	void *private_data) { return -ENXIO; }
>  static inline bool dmi_match(enum dmi_field f, const char *str)
>  	{ return false; }
>  static inline void dmi_memdev_name(u16 handle, const char **bank,


-- 
Jean Delvare
SUSE L3 Support