Mesa (master): docs: add some very basic documentation about zink

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Module: Mesa
Branch: master
Commit: fd20e986249f88129d81353d79dd248d7664953b
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=fd20e986249f88129d81353d79dd248d7664953b

Author: Erik Faye-Lund <erik.faye-lund at collabora.com>
Date:   Sun Jul 19 12:13:40 2020 +0200

docs: add some very basic documentation about zink

Reviewed-by: Eric Engestrom <eric at engestrom.ch>
Reviewed-By: Mike Blumenkrantz <michael.blumenkrantz at gmail.com>
Reviewed-by: Marcin Ślusarz <marcin.slusarz at intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5967>

---

 docs/gallium/drivers/zink.rst | 45 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/docs/gallium/drivers/zink.rst b/docs/gallium/drivers/zink.rst
new file mode 100644
index 00000000000..0756c52b232
--- /dev/null
+++ b/docs/gallium/drivers/zink.rst
@@ -0,0 +1,45 @@
+Zink
+====
+
+Overview
+--------
+
+The Zink driver is a Gallium driver that emits Vulkan API calls instead
+of targeting a specific GPU architecture. This can be used to get full
+desktop OpenGL support on devices that only support Vulkan.
+
+Debugging
+---------
+
+There's a few tools that are useful for debugging Zink, like this environment
+variable:
+
+.. envvar:: ZINK_DEBUG <flags> ("")
+
+``nir``
+   Print the NIR form of all shaders to stderr.
+``spirv``
+   Write the binary SPIR-V form of all compiled shaders to a file in the
+   current directory, and print a message with the filename to stderr.
+``tgsi``
+   Print the TGSI form of TGSI shaders to stderr.
+
+Vulkan Validation Layers
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+Another useful tool for debugging is the `Vulkan Validation Layers
+<https://github.com/KhronosGroup/Vulkan-ValidationLayers/blob/master/README.md>`_.
+
+The validation layers effectively insert extra checking between Zink and the
+Vulkan driver, pointing out incorrect usage of the Vulkan API. The layers can
+be enabled by setting the environment variable :envvar:`VK_INSTANCE_LAYERS` to
+"VK_LAYER_KHRONOS_validation". You can read more about the Validation Layers
+in the link above.
+
+IRC
+---
+
+In order to make things a bit easier to follow, we have decided to create our
+own IRC channel. If you're interested in contributing, or have any technical
+questions, don't hesitate to visit `#zink on FreeNode
+<irc://irc.freenode.net/zink>`_ and say hi!