From: Bruce Richardson <bruce.richardson@intel.com>
To: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
Cc: "Nélio Laranjeiro" <nelio.laranjeiro@6wind.com>,
"dev@dpdk.org" <dev@dpdk.org>,
"Olivier Matz" <olivier.matz@6wind.com>,
"Lu, Wenzhuo" <wenzhuo.lu@intel.com>,
"Adrien Mazarguil" <adrien.mazarguil@6wind.com>
Subject: Re: [dpdk-dev] [PATCH] net: introduce big and little endian types
Date: Tue, 6 Dec 2016 13:34:27 +0000 [thread overview]
Message-ID: <20161206133427.GB15416@bricha3-MOBL3.ger.corp.intel.com> (raw)
In-Reply-To: <2601191342CEEE43887BDE71AB9772583F0E46DC@irsmsx105.ger.corp.intel.com>
On Tue, Dec 06, 2016 at 12:41:00PM +0000, Ananyev, Konstantin wrote:
>
>
> > -----Original Message-----
> > From: Richardson, Bruce
> > Sent: Tuesday, December 6, 2016 11:55 AM
> > To: Ananyev, Konstantin <konstantin.ananyev@intel.com>
> > Cc: Nélio Laranjeiro <nelio.laranjeiro@6wind.com>; dev@dpdk.org; Olivier Matz <olivier.matz@6wind.com>; Lu, Wenzhuo
> > <wenzhuo.lu@intel.com>; Adrien Mazarguil <adrien.mazarguil@6wind.com>
> > Subject: Re: [dpdk-dev] [PATCH] net: introduce big and little endian types
> >
> > On Tue, Dec 06, 2016 at 11:23:42AM +0000, Ananyev, Konstantin wrote:
> > > Hi Neilo,
> > >
> > >
> > > Hi Neilo,
> > > > > >
> > > > > > This commit introduces new rte_{le,be}{16,32,64}_t types and updates
> > > > > > rte_{le,be,cpu}_to_{le,be,cpu}_*() and network header structures
> > > > > > accordingly.
> > > > > >
> > > > > > Specific big/little endian types avoid uncertainty and conversion mistakes.
> > > > > >
> > > > > > No ABI change since these are simply typedefs to the original types.
> > > > >
> > > > > It seems like quite a lot of changes...
> > > > > Could you probably explain what will be the benefit in return?
> > > > > Konstantin
> > > >
> > > > Hi Konstantin,
> > > >
> > > > The benefit is to provide documented byte ordering for data types
> > > > software is manipulating to determine when network to CPU (or CPU to
> > > > network) conversion must be performed.
> > >
> > > Ok, but is it really worth it?
> > > User can still make a mistake and forget to call ntoh()/hton() at some particular place.
> > > From other side most people do know that network protocols headers are usually in BE format.
> > > I would understand the effort, if we'll have some sort of tool that would do some sort of static code analysis
> > > based on these special types or so.
> > > Again, does it mean that we should go and change uint32_t to rte_le_32 inside all Intel PMDs
> > > (and might be in some others too) to be consistent?
> > > Konstantin
> > >
> >
> > I actually quite like this patch as I think it will help make things
> > clear when the user is possibly doing something wrong. I don't think we
> > need to globally change all PMDs to use the types, though.
>
> Ok, so where do you believe we should draw a line?
> Why let say inside lib/librte_net people should use these typedefs, but
> inside drivers/net/ixgbe they don't?
Because those are not public APIs. It would be great if driver writers
used the typedefs, but I don't think it should be mandatory.
>
> >
> > One thing I'm wondering though, is if we might want to take this
> > further. For little endian environments, we could define the big endian
> > types as structs using typedefs, and similarly the le types on be
> > platforms, so that assigning from the non-native type to the native one
> > without a transformation function would cause a compiler error.
>
> Not sure I understand you here.
> Could you possibly provide some example?
>
typedef struct {
short val;
} rte_be16_t;
That way if you try to assign a value of type rte_be16_t to a uint16_t
variable you'll get a compiler error, unless you use an appropriate
conversion function. In short, it changes things from not just looking
wrong - which is the main purpose of Neilo's patchset - to actually
making it incorrect from the compiler's point of view too.
/Bruce
next prev parent reply other threads:[~2016-12-06 13:34 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-09 15:04 Nelio Laranjeiro
2016-12-05 10:09 ` Ananyev, Konstantin
2016-12-05 12:06 ` Nélio Laranjeiro
2016-12-06 11:23 ` Ananyev, Konstantin
2016-12-06 11:55 ` Bruce Richardson
2016-12-06 12:41 ` Ananyev, Konstantin
2016-12-06 13:34 ` Bruce Richardson [this message]
2016-12-06 14:45 ` Ananyev, Konstantin
2016-12-06 14:56 ` Wiles, Keith
2016-12-06 15:34 ` Morten Brørup
2016-12-06 16:28 ` Nélio Laranjeiro
2016-12-06 16:31 ` Wiles, Keith
2016-12-06 16:36 ` Richardson, Bruce
2016-12-06 17:00 ` Ananyev, Konstantin
2016-12-06 17:29 ` Neil Horman
2016-12-06 13:14 ` Nélio Laranjeiro
2016-12-06 13:30 ` Bruce Richardson
2016-12-06 14:06 ` Wiles, Keith
2016-12-08 9:30 ` Nélio Laranjeiro
2016-12-08 13:59 ` Wiles, Keith
2016-12-08 16:06 ` Thomas Monjalon
2016-12-08 15:07 ` Neil Horman
2016-12-08 15:10 ` Ananyev, Konstantin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20161206133427.GB15416@bricha3-MOBL3.ger.corp.intel.com \
--to=bruce.richardson@intel.com \
--cc=adrien.mazarguil@6wind.com \
--cc=dev@dpdk.org \
--cc=konstantin.ananyev@intel.com \
--cc=nelio.laranjeiro@6wind.com \
--cc=olivier.matz@6wind.com \
--cc=wenzhuo.lu@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).