We use the C #define syntax to refer to numeric values. Let's document that. Signed-off-by: Michael S. Tsirkin <> --- changes from v1: address Cornelia's comments
introduction.tex
23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/introduction.tex b/introduction.tex index cc38e29..47bebf5 100644 --- a/introduction.tex +++ b/introduction.tex @@ -210,6 +210,29 @@ section{Structure Specifications} egin{lstlisting} CPU_TO_BE16(B << 15
A) end{lstlisting} +section{Constant Specifications} + +In many cases, numeric values used in the interface between the device +and the driver are documented using the C #define and /* */ +comment syntax. Multiple related values are grouped together with +a common name as a prefix, using _ as a separator. +Using _XXX as a suffix refers to all values in a group. +For example: + +egin{lstlisting} +/* Field Fld value A description */ +#define VIRTIO_FLD_A
(1 << 0) +/* Field Fld value B description */ +#define VIRTIO_FLD_B
(1 << 1) +end{lstlisting} +documents two numeric values for a field field{Fld}, with +field{Fld} having value 1 referring to field{A} and field{Fld} +having value 2 referring to field{B}. +Note that $<<$ refers to the shift-left operation. + +Further, in this case VIRTIO_FLD_A and VIRTIO_FLD_B +refer to values 1 and 2 of Fld respectively. Further, VIRTIO_FLD_XXX refers to +either VIRTIO_FLD_A or VIRTIO_FLD_B.
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MST
