netdev - Re: [PATCH ethtool-next 1/7] cmis: Fix CLEI code parsing

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Message-ID: <20210930202133.rspuswnnbnnhlgeb@lion.mk-sys.cz>
Date:   Thu, 30 Sep 2021 22:21:33 +0200
From:   Michal Kubecek <mkubecek@...e.cz>
To:     Ido Schimmel <idosch@...sch.org>
Cc:     netdev@...r.kernel.org, vadimp@...dia.com, moshe@...dia.com,
        popadrian1996@...il.com, mlxsw@...dia.com,
        Ido Schimmel <idosch@...dia.com>
Subject: Re: [PATCH ethtool-next 1/7] cmis: Fix CLEI code parsing

On Fri, Sep 17, 2021 at 05:40:37PM +0300, Ido Schimmel wrote:
> From: Ido Schimmel <idosch@...dia.com>
> 
> In CMIS, unlike SFF-8636, there is no presence indication for the CLEI
> code (Common Language Equipment Identification) field. The field is
> always present, but might not be supported. In which case, "a value of
> all ASCII 20h (spaces) shall be entered".
> 
> Therefore, remove the erroneous check which seems to be influenced from
> SFF-8636 and only print the string if it is supported and has a non-zero
> length.
> 
> Signed-off-by: Ido Schimmel <idosch@...dia.com>
> ---
>  cmis.c | 8 +++++---
>  cmis.h | 3 +--
>  2 files changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/cmis.c b/cmis.c
> index 1a91e798e4b8..2a48c1a1d56a 100644
> --- a/cmis.c
> +++ b/cmis.c
> @@ -307,6 +307,8 @@ static void cmis_show_link_len(const __u8 *id)
>   */
>  static void cmis_show_vendor_info(const __u8 *id)
>  {
> +	const char *clei = (const char *)(id + CMIS_CLEI_START_OFFSET);
> +
>  	sff_show_ascii(id, CMIS_VENDOR_NAME_START_OFFSET,
>  		       CMIS_VENDOR_NAME_END_OFFSET, "Vendor name");
>  	cmis_show_oui(id);
> @@ -319,9 +321,9 @@ static void cmis_show_vendor_info(const __u8 *id)
>  	sff_show_ascii(id, CMIS_DATE_YEAR_OFFSET,
>  		       CMIS_DATE_VENDOR_LOT_OFFSET + 1, "Date code");
>  
> -	if (id[CMIS_CLEI_PRESENT_BYTE] & CMIS_CLEI_PRESENT_MASK)
> -		sff_show_ascii(id, CMIS_CLEI_START_OFFSET,
> -			       CMIS_CLEI_END_OFFSET, "CLEI code");
> +	if (strlen(clei) && strcmp(clei, CMIS_CLEI_BLANK))
> +		sff_show_ascii(id, CMIS_CLEI_START_OFFSET, CMIS_CLEI_END_OFFSET,
> +			       "CLEI code");
>  }
>  
>  void qsfp_dd_show_all(const __u8 *id)

Is it safe to assume that the string will be always null terminated?
Looking at the code below, CMIS_CLEI_BLANK consists of 10 spaces which
would fill the whole block at offsets 0xBE through 0xC7 with spaces and
offset 0xC8 is used as CMIS_PWR_CLASS_OFFSET. Also, sff_show_ascii()
doesn't seem to expect a null terminated string, rather a space padded
one.

Michal


> diff --git a/cmis.h b/cmis.h
> index 78ee1495bc33..d365252baa48 100644
> --- a/cmis.h
> +++ b/cmis.h
> @@ -34,10 +34,9 @@
>  #define CMIS_DATE_VENDOR_LOT_OFFSET		0xBC
>  
>  /* CLEI Code (Page 0) */
> -#define CMIS_CLEI_PRESENT_BYTE			0x02
> -#define CMIS_CLEI_PRESENT_MASK			0x20
>  #define CMIS_CLEI_START_OFFSET			0xBE
>  #define CMIS_CLEI_END_OFFSET			0xC7
> +#define CMIS_CLEI_BLANK				"          "
>  
>  /* Cable assembly length */
>  #define CMIS_CBL_ASM_LEN_OFFSET			0xCA
> -- 
> 2.31.1
> 

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