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

[Yuanhan Liu <yliu@fridaylinux.org>]

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

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@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
 ~~~~~~~~~~~~
 
-- 
2.7.4