Re: [Xen-devel] [PATCH 1 of 2] libxl: Allow multiple USB devices on HVM domain creation

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2012-11-28 at 12:16 +0000, George Dunlap wrote:
> # HG changeset patch
> # User George Dunlap <george.dunlap@xxxxxxxxxxxxx>
> # Date 1354101445 0
> # Node ID 538d9ffbd71b41e8cf6d7da0ded9e0a0b07f3c0d
> # Parent  ae6fb202b233af815466055d9f1a635802a50855
> libxl: Allow multiple USB devices on HVM domain creation
> 
> This patch allows an HVM domain to be created with multiple USB
> devices.
> 
> Since the previous interface only allowed the passing of a single
> device, this requires us to add a new element to the hvm struct of
> libxl_domain_build_info -- usbdevice_list.  For API compatibility, the
> old element, usbdevice, remains.
> 
> If b_info->hvm.usbdevice is non-NULL, then it will be used exclusively;
> otherwise, libxl will check for b_info->hvm.usbdevice_list instead.

Is this the right way round? If the caller knows about usbdevice_list
enough to have set it to something then surely that's the one it wanted?

> Each device listed will cause an extra "-usbdevice [foo]" to be appended
> to the qemu command line.
> 
> In order to allow users of libxl to write software compatible with older
> versions of libxl, also define LIBXL_HAVE_BUILDINFO_USBDEVICE_LIST.  If
> this is present, the caller should use b_info->hvm.usbdevice_list; otherwise
> they should use b_info->hvm.usbdevice.

Actually it's a both stricter and looser than that, if
LIBXL_HAVE_BUILDINFO_USBDEVICE_LIST is defined then the caller can
choose to use usbdevice_list but can also use usbdevice if they wish
(but not both). If it is not present then they must not use
usbdevice_list at all.

I wonder if this LIBXL_HAVE should also be contained in a #ifdef
LIBXL_API_VERSION >= 0x040300?

> 
> Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>

> 
> diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
> --- a/tools/libxl/libxl.h
> +++ b/tools/libxl/libxl.h
> @@ -266,6 +266,23 @@
>  #endif
>  #endif
>  
> +/* 
> + * LIBXL_HAVE_BUILDINFO_USBDEVICE_LIST
> + * 
> + * If this is defined, then the libxl_domain_build_info structure will
> + * contain hvm.usbdevice_list, a libxl_string_list type that contains
> + * a list of USB devices to specify on the qemu command-line.
> + *
> + * If it is set, callers may use either hvm.usbdevice or
> + * hvm.usbdevice_list, but not both; if both are set, only
> + * hvm.usbdevice will be used.
> + *
> + * If this is not defined, callers should only use hvm.usbdevice.
> + * Note that this means only one device can be added at domain build
> + * time.
> + */
> +#define LIBXL_HAVE_BUILDINFO_USBDEVICE_LIST 1
> +
>  /* Functions annotated with LIBXL_EXTERNAL_CALLERS_ONLY may not be
>   * called from within libxl itself. Callers outside libxl, who
>   * do not #include libxl_internal.h, are fine. */
> diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
> --- a/tools/libxl/libxl_dm.c
> +++ b/tools/libxl/libxl_dm.c
> @@ -191,6 +191,15 @@ static char ** libxl__build_device_model
>              if (b_info->u.hvm.usbdevice) {
>                  flexarray_vappend(dm_args,
>                                    "-usbdevice", b_info->u.hvm.usbdevice, 
> NULL);
> +            } else if (b_info->u.hvm.usbdevice_list) {
> +                char **p;
> +                for (p = b_info->u.hvm.usbdevice_list;
> +                     *p;
> +                     p++) {
> +                    flexarray_vappend(dm_args,
> +                                      "-usbdevice",
> +                                      *p, NULL);
> +                }
>              }
>          }
>          if (b_info->u.hvm.soundhw) {
> diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
> --- a/tools/libxl/libxl_types.idl
> +++ b/tools/libxl/libxl_types.idl
> @@ -326,6 +326,7 @@ libxl_domain_build_info = Struct("domain
>                                         ("usbdevice",        string),
>                                         ("soundhw",          string),
>                                         ("xen_platform_pci", libxl_defbool),
> +                                       ("usbdevice_list",   
> libxl_string_list),
>                                         ])),
>                   ("pv", Struct(None, [("kernel", string),
>                                        ("slack_memkb", MemKB),
> 
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> http://lists.xen.org/xen-devel



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