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Subject: Re: [virtio] [PATCH] introduction: document #define syntax
On Tue, 16 Mar 2021 17:13:17 -0400 "Michael S. Tsirkin" <mst@redhat.com> wrote: > We use the C #define syntax to refer to numeric values. > Let's document that. > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > --- > 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 >
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