Re: [dpdk-dev] [PATCH v2] cmdline: rework as a wrapper to libedit

[Olivier Matz <olivier.matz@6wind.com>]

On Wed, Jun 27, 2018 at 11:36:28AM +0100, Bruce Richardson wrote:
> On Tue, Jun 26, 2018 at 03:21:21PM +0200, Olivier Matz wrote:
> > Hi Adrien,
> > 
> > Better late than never, please find below some comments
> > about your patch.
> > 
> > On Thu, Apr 19, 2018 at 05:13:53PM +0200, Adrien Mazarguil wrote:
> > > Disclaimer: this patch must not be confused with the CLI library [1]
> > > (work in progress) that will eventually supersede librte_cmdline itself
> > > with a different API.
> > > 
> > > Rather, it modifies librte_cmdline to delegate all the heavy lifting
> > > (terminal and history handling), strips unused features and re-implements
> > > what remains of its public API as a wrapper to the editline library (also
> > > known as libedit) [2], a well-known, BSD-licensed and widely available
> > > library used by many projects which does everything needed and more [3].
> > > 
> > > This approach was chosen because converting librte_cmdline as a wrapper to
> > > a more capable library was easier and faster than addressing its
> > > shortcomings and results in much less code to maintain in DPDK.
> > > 
> > > It also provides a drop-in solution for applications that rely on
> > > librte_cmdline. They benefit from greatly improved command line handling
> > > without a meaningful impact on their code base.
> > > 
> > > The main motivation behind this patch is testpmd's flow (rte_flow) command,
> > > which requires support for dynamic tokens and very long lines that must be
> > > broken down when displayed. This is not supported by librte_cmdline's
> > > limited terminal handling capabilities, resulting in a rather frustrating
> > > user experience.
> > > 
> > > It had to be addressed given the importance of testpmd as one of the
> > > primary tool used by PMD developers.
> > > 
> > > This rework results in the following changes:
> > > 
> > > - Removed circular buffer management interface for command history
> > >   (cmdline_cirbuf.c), command history being handled by libedit.
> > > - Removed raw command-line interpreter (cmdline_rdline.c).
> > > - Removed raw terminal handler (cmdline_vt100.c).
> > > - Removed all test/example code for the above.
> > > - Re-implemented high level interactive and non-interactive command-line
> > >   handlers (cmdline.c and cmdline_socket.c) on top of libedit using its
> > >   native interface, not its readline compatibility layer.
> > > - Made struct cmdline opaque so that applications relying on librte_cmdline
> > >   do not need to include any libedit headers.
> > > - Applications do not need to include cmdline_rdline.h anymore.
> > > - Terminal resizing is now automatically handled.
> > > - New external dependency for applications relying on librte_cmdline.
> > > - Major version bump due to the ABI impact of these changes.
> > > 
> > > [1] http://dpdk.org/browse/draft/dpdk-draft-cli/
> > > [2] http://thrysoee.dk/editline/
> > > [3] http://netbsd.gw.com/cgi-bin/man-cgi?editline++NetBSD-current
> > > 
> > > Signed-off-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>
> > > Cc: Olivier Matz <olivier.matz@6wind.com>
> > > Cc: Keith Wiles <keith.wiles@intel.com>
> > > Cc: Jingjing Wu <jingjing.wu@intel.com>
> > > Cc: Thomas Monjalon <thomas@monjalon.net>
> > > Cc: Ferruh Yigit <ferruh.yigit@intel.com>
> > > Cc: Jim Thompson <jim@netgate.com>
> > > Cc: Anatoly Burakov <anatoly.burakov@intel.com>
> > > 
> > > --
> > > 
> > > v2 changes:
> > > 
> > > - Replaced an instance of snprintf() with rte_strlcpy() [5].
> > > - Rebased patch.
> > > 
> > > [5] http://dpdk.org/ml/archives/dev/2018-April/097721.html
> > > 
> > > v1 changes:
> > > 
> > > No fundamental change since the original RFC [4], except it's been rebased
> > > several times and Meson build support was added in the meantime. Commit log
> > > was also shortened a bit.
> > > 
> > > I'm re-sending this because I think it's useful, at least to me (duh). As
> > > the maintainer of rte_flow, I spend most of my time typing flow commands in
> > > testpmd and libedit makes that a pleasant experience.
> > > 
> > > Try it out! And don't hesitate to send your acked-by line to get this in
> > > time for 18.05 :)
> > > 
> > > [4] http://dpdk.org/ml/archives/dev/2017-November/081605.html
> > 
> > Re-saying what I said the first time: I think this is a very good
> > improvement, removing lots of dpdk code that is better implemented in
> > well-known libraries.
> > 
> > 
> > The compilation with shared libraries fail. Please try for instance:
> > ./devtools/test-build.sh -j4 x86_64-native-linuxapp-clang+shared+debug
> > 
> > I suggest to add in lib/librte_cmdline/Makefile:
> > 
> >   LDLIBS += $(shell pkg-config --libs libedit)
> > 
> > 
> > I also think something should be added in
> > /doc/guides/linux_gsg/sys_reqs.rst to highlight the new build
> > dependency.
> > 
> > 
> > I noticed a bad behavior change (in addition to many good ones):
> > ctrl-c now quits the application, and this was not the case before.
> > I often use ctrl-c to delete the line I'm currently editing. Please
> > see at the end a proposition to restore this feature.
> > 
> 
> I 100% disagree, please set things up that "ctrl-c" quits the application.
> 
> Having our DPDK testpmd and auto-test apps fail to close on ctrl-c is just
> awful from a usability perspective IMHO! If there is ever a problem with
> the app and you need to kill it quickly, e.g. you want to stop one of those
> long-running autotests, the lack of ctrl-c is a pain.

Well, this is a good argument.

It looks that ctrl-u can do the job, so I may just need to change my
habits :)

Olivier