pkg, prog: add per-field direction attribute

2 files changed, 27 insertions, 6 deletions

diff --git a/docs/syscall_descriptions.md b/docs/syscall_descriptions.md
index d3f8f5d17..3fe18b904 100644
--- a/docs/syscall_descriptions.md
+++ b/docs/syscall_descriptions.md
@@ -169,10 +169,9 @@ close(r0)
 ```
 
 Syscall arguments are always `in`, return values are `out` and pointer indirections
-have explicit direction as `ptr` type attribute. Note: for pointer indirections
-the direction applies to the whole pointee, and it's not possible to specify the
-direction individually for struct fields at the moment
-(see [#245](https://github.com/google/syzkaller/issues/245)).
+have explicit direction as `ptr` type attribute. Also, it is possible to specify
+direction attribute individually for struct fields to account for more complex 
+producer/consumer scenarious with structs that include both input/output resources.
 
 <div id="values"/>
 
diff --git a/docs/syscall_descriptions_syntax.md b/docs/syscall_descriptions_syntax.md
index 7f4033079..5af302de8 100644
--- a/docs/syscall_descriptions_syntax.md
+++ b/docs/syscall_descriptions_syntax.md
@@ -120,10 +120,14 @@ Structs are described as:
 
 ```
 structname "{" "\n"
-	(fieldname type "\n")+
+	(fieldname type ("(" fieldattribute* ")")? "\n")+
 "}" ("[" attribute* "]")?
 ```
 
+Fields can have attributes specified in parentheses after the field, independent
+of their type. The only attribute is direction (`in/out/inout`). For the field for
+which it is specified, the direction attributes on the upper levels are overridden.
+
 Structs can have attributes specified in square brackets after the struct.
 Attributes are:
 
@@ -137,10 +141,12 @@ Unions are described as:
 
 ```
 unionname "[" "\n"
-	(fieldname type "\n")+
+	(fieldname type ("(" fieldattribute* ")")? "\n")+
 "]" ("[" attribute* "]")?
 ```
 
+Field attributes are as defined for [structs](#structs).
+
 Unions can have attributes specified in square brackets after the union.
 Attributes are:
 
@@ -181,6 +187,22 @@ test_struct {
 }
 ```
 
+For more complex producer/consumer scenarios, field attributes can be utilized.
+For example:
+
+```
+resource my_resource_1[int32]
+resource my_resource_2[int32]
+
+request_produce1_consume2(..., arg ptr[inout, test_struct])
+
+test_struct {
+	...
+	field0	my_resource_1	(out)
+	field1	my_resource_2	(in)
+}
+```
+
 ## Type Aliases
 
 Complex types that are often repeated can be given short type aliases using the