linux-kernel - Re: [PATCH 04/14] ABI: better identificate tables

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Date:   Wed, 19 Jun 2019 17:02:07 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Mauro Carvalho Chehab <mchehab+samsung@...nel.org>
Cc:     Johan Hovold <johan@...nel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        Mauro Carvalho Chehab <mchehab@...pensource.com>,
        Mauro Carvalho Chehab <mchehab@...radead.org>,
        linux-kernel@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        Stefan Achatz <erazor_de@...rs.sourceforge.net>
Subject: Re: [PATCH 04/14] ABI: better identificate tables

On Wed, Jun 19, 2019 at 10:56:33AM -0300, Mauro Carvalho Chehab wrote:
> Hi Johan,
> 
> Em Wed, 19 Jun 2019 14:51:35 +0200
> Johan Hovold <johan@...nel.org> escreveu:
> 
> > On Thu, Jun 13, 2019 at 11:04:10PM -0300, Mauro Carvalho Chehab wrote:
> > > From: Mauro Carvalho Chehab <mchehab@...pensource.com>
> > > 
> > > When parsing via script, it is important to know if the script
> > > should consider a description as a literal block that should
> > > be displayed as-is, or if the description can be considered
> > > as a normal text.
> > > 
> > > Change descriptions to ensure that the preceding line of a table
> > > ends with a colon. That makes easy to identify the need of a
> > > literal block.  
> > 
> > In the cover letter you say that the first four patches of this series,
> > including this one, "fix some ABI descriptions that are violating the
> > syntax described at Documentation/ABI/README". This seems a bit harsh,
> > given that it's you that is now *introducing* a new syntax requirement
> > to assist your script.
> 
> Yeah, what's there at the cover letter doesn't apply to this specific
> patch. The thing is that I wrote this series a lot of time ago (2016/17).
> 
> I revived those per a request at KS ML, as we still need to expose the
> ABI content on some book that will be used by userspace people.
> 
> So, I just rebased it on the top of curent Kernel, add a cover letter
> with the things I remembered and re-sent.
> 
> In the specific case of this patch, the ":" there actually makes sense
> for someone that it is reading it as a text file, and it is an easy
> hack to make it parse better.
> 
> > Specifically, this new requirement isn't documented anywhere AFAICT, so
> > how will anyone adding new ABI descriptions learn about it?
> 
> Yeah, either that or provide an alternative to "Description" tag, to be
> used with more complex ABI descriptions.
> 
> One of the things that occurred to me, back on 2017, is that we should
> have a way to to specify that an specific ABI description would have
> a rich format. Something like:
> 
> What:		/sys/bus/usb/devices/<busnum>-<devnum>:<config num>.<interface num>/<hid-bus>:<vendor-id>:<product-id>.<num>/pyra/roccatpyra<minor>/actual_cpi
> Date:		August 2010
> Contact:	Stefan Achatz <erazor_de@...rs.sourceforge.net>
> RST-Description:
> 		It is possible to switch the cpi setting of the mouse with the
> 		press of a button.
> 		When read, this file returns the raw number of the actual cpi
> 		setting reported by the mouse. This number has to be further
> 		processed to receive the real dpi value:
> 
> 		===== =====
> 		VALUE DPI
> 		===== =====
> 		1     400
> 		2     800
> 		4     1600
> 		===== =====
> 
> With that, the script will know that the description contents will be using
> the ReST markup, and parse it accordingly. Right now, what it does, instead,
> is to place the description on a code-block, e. g. it will produce this
> output for the description:
> 
> ::
> 
> 		It is possible to switch the cpi setting of the mouse with the
> 		press of a button.
> 		When read, this file returns the raw number of the actual cpi
> 		setting reported by the mouse. This number has to be further
> 		processed to receive the real dpi value:
> 
> 		VALUE DPI
> 		1     400
> 		2     800
> 		4     1600
> 
> 
> Greg, 
> 
> what do you think?

I don't know when "Description" and "RST-Description" would be used.
Why not just parse "Description" like rst text and if things are "messy"
we fix them up as found, like you did with the ":" here?  It doesn't
have to be complex, we can always fix them up after-the-fact if new
stuff gets added that doesn't quite parse properly.

Just like we do for most kernel-doc formatting :)

thanks,

greg k-h