Re: [PATCH] doc: document the new devargs syntax

[Thomas Monjalon <thomas@monjalon.net>]

24/01/2018 16:24, Yuanhan Liu:
> On Tue, Jan 23, 2018 at 05:08:16PM +0100, Gaëtan Rivet wrote:
> > Drivers answers to a specific API (ethdev, cryptodev, ...), to create
> > standardized objects in response to parameters that are given to them
> > for init. I think matching properties should be restricted to higher
> > classes (bus, eth/crypto),
> 
> That's also what I thought. But I'm okay to have "driver" category
> included for matching. I just don't really see a good example for that.
> 
> > while the driver class should be left
> > free-form and to the responsibility of the PMD itself (while having the
> > proper libraries for helping parsing safely, thus driving developpers
> > toward similar syntaxes, while not forcing them in those).
> 
> I agree. The drv args are parsed by the drivers after all. It's hard to
> have a good parser for all. I also don't know why we have to force them
> to use "key=value" pairs.
> 
> I even see some drawbacks from the forcement:
> 
> - some PMDs already use none key/value format. Forcing them breaks more.
>   If the "-w" "--vdev" compatibility is kept", nothing will be broken
>   from the user point of view. However, if "key=value" pair is going to
>   be used, user have to do some changes.
> 
> - Some "value" might have to use the nested "=". Handling the nested pairs
>   introduces more complexity.
> 
> - sometimes, it's simple without an assignment. For example, it could be
>   "driver=vhost-pmd,...,client" to let the vhost PMD acts as the client
>   mode.
> 
> Both Linux kernel and QEMU don't force the "key=value" pair usage, I don't
> see any good reason why we have to do that.

OK