[dpdk-dev] [PATCH] doc: document the new devargs syntax

[Yuanhan Liu]

On Wed, Jan 17, 2018 at 12:34:08PM +0000, Ferruh Yigit wrote:
> On 1/16/2018 2:50 PM, Yuanhan Liu wrote:
> > This patch documents the new devargs syntax, which is going to be
> > implemented in DPDK v18.05.
> > 
> > The new devargs proposal is introduced for having a consistent
> > interface for:
> > 
> > - whitelisting/blacklisting devices
> > - identifying ports
> > - attaching/detaching devices
> 
> Hi Yuanhan,

Hi Ferruh,

> devargs = device arguments, the PMD specific arguments, similar to module_param
> in Linux.

Not exactly. If you look at the function
rte_eth_dev_attach(const char *devargs, uint16_t *port_id), the "device
identifier" part you called also part of the devargs.

> 
> Currently only "--vdev" and -w/-b eal parameters parse proceeding strings as
> devargs.
> 
> Like: "--vdev "net_pcap,iface=lo" .
> For this case "iface=lo" device specific argument and available to use from pcap
> PMD.
> 
> I agree it to have a consistent way to describe device, that makes better
> whitelist/blacklist support. But that part is not device args, more like device
> identifier.
> 
> When you use this string with whitelist/blacklist I think you won't need
> "iface=lo" part,

Right. That's actaully mentioned in this patch:

   Before device is probed, only the bus category is relevant.

> only need first part. And when using with --vdev, (or perhaps
> with attach) you don't need to use first part
> "bus=pci,id=0000:01:00.0/class=eth,mac=00:11:22:33:44:55", PMD already knows it
> is in virtual bus and its class etc.

We are going to keep the compatibily, meaning we will leave "-w" and
"--vdev" as they are. We plan to introduce one more CLI option and
let user to switch to it so that it can work with any bus, not only
PCI and vdev bus.

> So does it make sense to separate them logically? Perhaps as "device identifier"
> and "device args".

Then I think it returns back to the old issue: how could we identify a
port when the bus id (say BDF for PCI bus) is not enough for identifying
a port? Such case could happen when a single NIC has 2 ports sharing
the same BDF. It could also happen with the VF representors that will
be introduced shortly.

	--yliu

> string can become:
> "device=bus=pci,id=0000:01:00.0/class=eth,mac=00:11:22:33:44:55;driver=PMD_NAME,driverspecificproperty=VALUE"
> 
> specific usages can become:
> -w "device=bus=pci,id=0000:01:00.0/class=eth,mac=00:11:22:33:44:55"
> --vdev "driver=PMD_NAME,driverspecificproperty=VALUE"
> 
> And store them in two separate storage, and eal or PMD can ask for "device
> identifier" or "device args" separately?
> 
> What do you think?
> 
> > 
> > Please check the patch content for the details. Also, here is link
> > for the background:
> >     http://dpdk.org/ml/archives/dev/2017-November/082600.html
> > 
> > This syntax is suggestd by Thomas:
> >     http://dpdk.org/ml/archives/dev/2017-December/084234.html
> > 
> > Signed-off-by: Yuanhan Liu <yliu at fridaylinux.org>
> > ---
> >  doc/guides/prog_guide/env_abstraction_layer.rst | 34 +++++++++++++++++++++++++
> >  1 file changed, 34 insertions(+)
> > 
> > diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst
> > index 34d871c..12f37f2 100644
> > --- a/doc/guides/prog_guide/env_abstraction_layer.rst
> > +++ b/doc/guides/prog_guide/env_abstraction_layer.rst
> > @@ -213,6 +213,40 @@ device having emitted a Device Removal Event. In such case, calling
> >  callback. Care must be taken not to close the device from the interrupt handler
> >  context. It is necessary to reschedule such closing operation.
> >  
> > +Devargs
> > +~~~~~~~
> > +
> > +The ``devargs`` can be used for whitelisting/blacklisting devices, identifying
> > +DPDK ports and attaching/deatching devices. They all share the same syntax.
> > +
> > +It is split in 3 categories, where almost everything is optional key/value pairs:
> > +
> > +* bus (pci, vdev, vmbus, fslmc, etc)
> > +* class (eth, crypto, etc)
> > +* driver (i40e, mlx5, virtio, etc)
> > +
> > +The key/value pair describing the category scope is mandatory and must be the
> > +first pair in the category properties. Example: bus=pci, must be placed before
> > +id=0000:01:00.0.
> > +
> > +The syntax has below rules:
> > +
> > +* Between categories, the separator is a slash.
> > +* Inside a category, the separator is a comma.
> > +* Inside a key/value pair, the separator is an equal sign.
> > +* Each category can be used alone.
> > +
> > +Here is an example with all categories::
> > +
> > +    bus=pci,id=0000:01:00.0/class=eth,mac=00:11:22:33:44:55/driver=PMD_NAME,driverspecificproperty=VALUE
> > +
> > +It can also be simple like below::
> > +
> > +    class=eth,mac=00:11:22:33:44:55
> > +
> > +A device is identified when every properties are matched. Before device is
> > +probed, only the bus category is relevant.
> > +
> >  Blacklisting
> >  ~~~~~~~~~~~~
> >  
> >