[PATCH v2 1/2] docs: fusa: Define the requirements for XEN_VERSION hypercall.

[Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>]

In the current patch, we have defined the requirements which are common for
all the commands.

Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>
---
Changes from -

v1 - 1. Fixed `XenProd~version_hyp_ret_val~1` requirement as Xen does not return
0 for success in all the cases.
2. Reworded the requirements so as to write them from Xen's perspective (not
domain's perspective).

 .../fusa/reqs/design-reqs/arm64/hypercall.rst | 55 +++++++++++++++++
 docs/fusa/reqs/index.rst                      |  2 +
 docs/fusa/reqs/market-reqs/reqs.rst           | 16 +++++
 .../reqs/product-reqs/version_hypercall.rst   | 61 +++++++++++++++++++
 4 files changed, 134 insertions(+)
 create mode 100644 docs/fusa/reqs/design-reqs/arm64/hypercall.rst
 create mode 100644 docs/fusa/reqs/product-reqs/version_hypercall.rst

diff --git a/docs/fusa/reqs/design-reqs/arm64/hypercall.rst 
b/docs/fusa/reqs/design-reqs/arm64/hypercall.rst
new file mode 100644
index 0000000000..ffd883260c
--- /dev/null
+++ b/docs/fusa/reqs/design-reqs/arm64/hypercall.rst
@@ -0,0 +1,55 @@
+.. SPDX-License-Identifier: CC-BY-4.0
+
+Hypercall
+=========
+
+Instruction
+-----------
+
+`XenSwdgn~arm64_hyp_instr~1`
+
+Description:
+Xen shall treat domain hypercall exception as hypercall requests.
+
+Rationale:
+
+Comments:
+Hypercall is one of the communication mechanism between Xen and domains.
+Domains use hypercalls for various requests to Xen.
+Domains use 'hvc' instruction to invoke hypercalls.
+
+Covers:
+ - `XenProd~version_hyp_first_param~1`
+ - `XenProd~version_hyp_second_param~1`
+
+Parameters
+----------
+
+`XenSwdgn~arm64_hyp_param~1`
+
+Description:
+Xen shall use x0 to read the first parameter, x1 for second parameter and so
+on, for domain hypercall requests.
+
+Rationale:
+
+Comments:
+
+Covers:
+ - `XenProd~version_hyp_first_param~1`
+ - `XenProd~version_hyp_second_param~1`
+
+Return value
+------------
+
+`XenSwdgn~arm64_ret_val~1`
+
+Description:
+Xen shall store the return value in x0 register.
+
+Rationale:
+
+Comments:
+
+Covers:
+ - `XenProd~version_hyp_ret_val~1`
diff --git a/docs/fusa/reqs/index.rst b/docs/fusa/reqs/index.rst
index 1088a51d52..d8683edce7 100644
--- a/docs/fusa/reqs/index.rst
+++ b/docs/fusa/reqs/index.rst
@@ -10,5 +10,7 @@ Requirements documentation
    market-reqs/reqs
    product-reqs/reqs
    product-reqs/arm64/reqs
+   product-reqs/version_hypercall
    design-reqs/arm64/generic-timer
    design-reqs/arm64/sbsa-uart
+   design-reqs/arm64/hypercall
diff --git a/docs/fusa/reqs/market-reqs/reqs.rst 
b/docs/fusa/reqs/market-reqs/reqs.rst
index 2d297ecc13..0e29fe5362 100644
--- a/docs/fusa/reqs/market-reqs/reqs.rst
+++ b/docs/fusa/reqs/market-reqs/reqs.rst
@@ -79,3 +79,19 @@ Comments:
 
 Needs:
  - XenProd
+
+Version hypercall
+-----------------
+
+`XenMkt~version_hypercall~1`
+
+Description:
+Xen shall provide an interface for the domains to retrieve Xen's version, type
+and compilation information.
+
+Rationale:
+
+Comments:
+
+Needs:
+ - XenProd
diff --git a/docs/fusa/reqs/product-reqs/version_hypercall.rst 
b/docs/fusa/reqs/product-reqs/version_hypercall.rst
new file mode 100644
index 0000000000..03221f70c3
--- /dev/null
+++ b/docs/fusa/reqs/product-reqs/version_hypercall.rst
@@ -0,0 +1,61 @@
+.. SPDX-License-Identifier: CC-BY-4.0
+
+Version hypercall
+=================
+
+First Parameter
+---------------
+
+`XenProd~version_hyp_first_param~1`
+
+Description:
+Xen shall treat the first argument (as an integer) to denote the command number
+for the hypercall.
+
+Rationale:
+
+Comments:
+
+Covers:
+ - `XenMkt~version_hypercall~1`
+
+Needs:
+ - XenSwdgn
+
+Second Parameter
+----------------
+
+`XenProd~version_hyp_second_param~1`
+
+Description:
+Xen shall treat the second argument as a virtual address to buffer in domain's
+memory.
+
+Rationale:
+
+Comments:
+
+Covers:
+ - `XenMkt~version_hypercall~1`
+
+Needs:
+ - XenSwdgn
+
+Return Value
+------------
+
+`XenProd~version_hyp_ret_val~1`
+
+Description:
+In case the hypercall fails, Xen shall return one of the error codes defined
+in 
http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/include/public/errno.h.
+
+Rationale:
+
+Comments:
+
+Covers:
+ - `XenMkt~version_hypercall~1`
+
+Needs:
+ - XenSwdgn
\ No newline at end of file
-- 
2.25.1