[PATCH] bpf, docs: Add note about type convention

[dthaler1968@googlemail.com]

From: Dave Thaler <dthaler@microsoft.com>

Add explanation about use of "u64", "u32", etc. as
the type convention used in BPF documentation.

Signed-off-by: Dave Thaler <dthaler@microsoft.com>
---
V2 -> V3: updated commit message to respond to David Vernet

V1 -> V2: addressed comments from Alexei and Stanislav
by using u64 instead of uint64_t
---
 Documentation/bpf/instruction-set.rst | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Documentation/bpf/instruction-set.rst b/Documentation/bpf/instruction-set.rst
index 2d3fe59bd26..77990c97b5e 100644
--- a/Documentation/bpf/instruction-set.rst
+++ b/Documentation/bpf/instruction-set.rst
@@ -7,6 +7,11 @@ eBPF Instruction Set Specification, v1.0
 
 This document specifies version 1.0 of the eBPF instruction set.
 
+Documentation conventions
+=========================
+
+For brevity, this document uses the type notion "u64", "u32", etc.
+to mean an unsigned integer whose width is the specified number of bits.
 
 Registers and calling convention
 ================================
@@ -123,6 +128,8 @@ the destination register is unchanged whereas for ``BPF_ALU`` the upper
 
   dst_reg = (u32) dst_reg + (u32) src_reg;
 
+where '(u32)' indicates that the upper 32 bits are zeroed.
+
 ``BPF_ADD | BPF_X | BPF_ALU64`` means::
 
   dst_reg = dst_reg + src_reg
-- 
2.33.4