OASIS Mailing List ArchivesView the OASIS mailing list archive below
or browse/search using MarkMail.


Help: OASIS Mailing Lists Help | MarkMail Help

virtio message

[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]

Subject: [PATCH v9 01/16] introduction: document bitfield notation

Bitfields are a useful and familiar way to specify sub-byte structure
layout. The only issue is that bitfield order isn't portable across
architectures.  Document that we list bitfields from least to
most significant one, and warn about portability issues.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
 introduction.tex | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/introduction.tex b/introduction.tex
index 979881e..3cb7a70 100644
--- a/introduction.tex
+++ b/introduction.tex
@@ -157,5 +157,23 @@ in little-endian byte order.
 in big-endian byte order.
+When documenting sub-byte data fields, C-like bitfield notation
+is used. Fields within an integer are always listed in order,
+from the least significant to the most significant bit.
+For example:
+be16 A : 15;
+be16 B : 1;
+documents the value A stored in the low 15 bit of a 16 bit
+integer and the value B stored in the high bit of the 16 bit
+integer, the integer in turn using the big-endian byte order.
+Note that this notation typically matches the way bitfields are
+packed by C compilers on little-endian architectures but not the
+way bitfields are packed by C compilers on big-endian

[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]