Re: [Qemu-stable] [PATCH 4/4] qapi: Rename ChardevBackend member "memory" to "ringbuf"

[Amos Kong]

On Mon, Jul 01, 2013 at 11:28:58AM +0200, Markus Armbruster wrote:
> Amos Kong <address@hidden> writes:
> 
> > On Mon, Jul 01, 2013 at 10:10:40AM +0200, Markus Armbruster wrote:
> >> Amos Kong <address@hidden> writes:
> >> 
> >> > On Fri, Jun 28, 2013 at 07:19:39PM +0200, Markus Armbruster wrote:
> >> >> Eric Blake <address@hidden> writes:
> >> >> 
> >> >> > On 06/27/2013 08:22 AM, Markus Armbruster wrote:
> >> >> >> Commit 1da48c6 called the new member "memory" after commit 3949e59
> >> >> >> standardized "ringbuf".  Rename for consistency.
> >> >> >> 
> >> >> >> However, member name "memory" is visible in QMP since 1.5.  It's
> >> >> >> undocumented just like the driver name.  Keep it working anyway.
> >> >> >> 
> >> >> >> Cc: address@hidden
> >> >> >> Signed-off-by: Markus Armbruster <address@hidden>
> >> >> >> ---
> >> >> >>  qapi-schema.json |  6 ++++--
> >> >> >>  qemu-char.c      | 11 ++++++-----
> >> >> >>  2 files changed, 10 insertions(+), 7 deletions(-)
> >> >> >> 
> >> >> >> diff --git a/qapi-schema.json b/qapi-schema.json
> >> >> >> index 6445da6..b3df8a5 100644
> >> >> >> --- a/qapi-schema.json
> >> >> >> +++ b/qapi-schema.json
> >> >> >> @@ -3277,9 +3277,9 @@
> >> >> >>  ##
> >> >> >>  # @ChardevRingbuf:
> >> >> >>  #
> >> >> >> -# Configuration info for memory chardevs
> >> >> >> +# Configuration info for ring buffer chardevs.
> >> >> >>  #
> >> >> >> -# @size: #optional Ringbuffer size, must be power of two, default 
> >> >> >> is 65536
> >> >> >> +# @size: #optional ring buffer size, must be power of two, default 
> >> >> >> is 65536
> >> >> >>  #
> >> >> >>  # Since: 1.5
> >> >> >>  ##
> >> >> >> @@ -3310,6 +3310,8 @@
> >> >> >>                                         'spicevmc' : 
> >> >> >> 'ChardevSpiceChannel',
> >> >> >>                                         'spiceport' : 
> >> >> >> 'ChardevSpicePort',
> >> >> >>                                         'vc'     : 'ChardevVC',
> >> >> >> +                                       'ringbuf': 'ChardevRingbuf',
> >> >> >> +                                       # next one is just for 
> >> >> >> compatibility
> >> >> >>                                         'memory' : 'ChardevRingbuf' 
> >> >> >> } }
> >> >> >
> >> >> > Does JSON allow comments in the middle of content?  Is this going to
> >> >> > screw up Amos' work on introspection?  You may need to instead have a
> >> >> > comment before the open '{' stating that 'memory' is an alias within 
> >> >> > the
> >> >> > union for back-compat reasons.
> >> >
> >> > I didn't parse the json file by myself. I just used the parsed
> >> > dictionary. So it only needs to make qapi.py happy.
> >> >
> >> >> RFC 4627 doesn't do comments at all.
> >> >> 
> >> >> This file is parsed by scripts/qapi.py, which as far as I can tell
> >> >> ignores lines starting with '#' anywhere in the input.
> >> >
> >> > Not anywhere, only start with '#'
> >> 
> >> Isn't that what I said?
> >> 
> >> > | def parse_schema(fp):
> >> > |     exprs = []
> >> > |     raw_exprs = []
> >> > |     expr = ''
> >> > |     expr_eval = None
> >> > | 
> >> > |     for line in fp:
> >> > |         if line.startswith('#') or line == '\n':
> >> >
> >> >       # ignores lines starting with '#' anywhere
> >> >           if line.strip().startswith('#')   
> >> >
> >> > |             continue
> >> > | 
> >> >
> >> >
> >> > So we should not add this kind of comment for back-compat.
> >> 
> >> Now I'm confused.  My patch adds a line that starts with '#'.
> >> parse_schema() ignores it.  Works as designed.  Why do you think we
> >> shouldn't do that?
> >
> > The comment line in your patch doen't start with '#', it starts with
> > blank-space. If we want qapi.py to process it, we need to do strip()
> > first.
> 
> Aha.  I agree with your reading of parse_schema().  However, I get
> exactly identical generated files with and without this comment.

I tried to add a '#hello' prefix for 'serial' item, but 'serial' can still
be parsed as before. The '#hello' prefix will be ignored in qapi.py:tokenize()

  { 'union': 'ChardevBackend', 'data': { 'file'   : 'ChardevFile',
                                         #hello 'serial' : 'ChardevHostdev',
                                         'parallel': 'ChardevHostdev',
   

> Michael, Anthony, can you explain why?
> 
> Any particular reason for requiring comments to start in column 0?

-- 
                        Amos.