diff options
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/devel/decodetree.rst | 8 | ||||
| -rw-r--r-- | docs/qemu-block-drivers.texi | 4 |
2 files changed, 9 insertions, 3 deletions
diff --git a/docs/devel/decodetree.rst b/docs/devel/decodetree.rst index 44ac621ea8..ce7f52308f 100644 --- a/docs/devel/decodetree.rst +++ b/docs/devel/decodetree.rst @@ -23,7 +23,7 @@ Fields Syntax:: - field_def := '%' identifier ( unnamed_field )+ ( !function=identifier )? + field_def := '%' identifier ( unnamed_field )* ( !function=identifier )? unnamed_field := number ':' ( 's' ) number For *unnamed_field*, the first number is the least-significant bit position @@ -34,6 +34,12 @@ present, they are concatenated. In this way one can define disjoint fields. If ``!function`` is specified, the concatenated result is passed through the named function, taking and returning an integral value. +One may use ``!function`` with zero ``unnamed_fields``. This case is called +a *parameter*, and the named function is only passed the ``DisasContext`` +and returns an integral value extracted from there. + +A field with no ``unnamed_fields`` and no ``!function`` is in error. + FIXME: the fields of the structure into which this result will be stored is restricted to ``int``. Which means that we cannot expand 64-bit items. diff --git a/docs/qemu-block-drivers.texi b/docs/qemu-block-drivers.texi index 91ab0eceae..c02547e28c 100644 --- a/docs/qemu-block-drivers.texi +++ b/docs/qemu-block-drivers.texi @@ -31,8 +31,8 @@ Supported options: @item preallocation Preallocation mode (allowed values: @code{off}, @code{falloc}, @code{full}). @code{falloc} mode preallocates space for image by calling posix_fallocate(). -@code{full} mode preallocates space for image by writing zeros to underlying -storage. +@code{full} mode preallocates space for image by writing data to underlying +storage. This data may or may not be zero, depending on the storage location. @end table @item qcow2 |