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

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Date:   Thu, 30 Sep 2021 23:41:02 +0300
From:   Ido Schimmel <idosch@...sch.org>
To:     Michal Kubecek <mkubecek@...e.cz>
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 Thu, Sep 30, 2021 at 10:21:33PM +0200, Michal Kubecek wrote:
> 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?

No. You want to see strnlen() and strncmp() instead?

> 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
> >