On Tue, 16 Mar 2021 17:13:17 -0400
"Michael S. Tsirkin" <> wrote:
> We use the C #define syntax to refer to numeric values.
> Let's document that.
>
> Signed-off-by: Michael S. Tsirkin <>
> ---
> introduction.tex | 21 +++++++++++++++++++++
> 1 file changed, 21 insertions(+)
>
> diff --git a/introduction.tex b/introduction.tex
> index cc38e29..4febed2 100644
> --- a/introduction.tex
> +++ b/introduction.tex
> @@ -210,6 +210,27 @@ \section{Structure Specifications}
> \begin{lstlisting}
> CPU_TO_BE16(B << 15 | A)
> \end{lstlisting}
> +\section{Constant Specifications}
> +
> +In many cases, numberic values used in the interface between the device
s/numberic/numeric/
> +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:
> +
> +\begin{lstlisting}
> +/* Value A description */
> +#define VIRTIO_VALUE_A
(1 << 0)
> +/* Value B description */
> +#define VIRTIO_VALUE_B
(1 << 1)
> +\end{lstlisting}
> +documents two numeric values: 1 meaning Value A and 2 meaning
> +Value B.
Doesn't that really document that Value A *is* 1? I'm a bit confused by
that sentence.
> Note that $<<$ refers to the shift-left operation.
> +
> +Further, in this case VIRTIO_VALUE_A and VIRTIO_VALUE_B
> +refer to 1 and 2 respectively. Further, VIRTIO_VALUE_XXX refers to
> +either VIRTIO_VALUE_A or VIRTIO_VALUE_B.
>
> \newpage
>
