On Tue, Mar 16, 2021 at 10:13 PM Michael S. Tsirkin <[email protected]> wrote: > > We use the C #define syntax to refer to numeric values. > Let's document that. > > Signed-off-by: Michael S. Tsirkin <[email protected]> > --- > 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 > +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. Note that $<<$ refers to the shift-left operation.
I'm not sure if somebody can be confused about this, but maybe s/shift-left operation/shift-left bitwise operation/ is more clear? > + > +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 > > -- > MST > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [email protected] > For additional commands, e-mail: [email protected] > --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
