Re: [libvirt] [PATCH v3] Add support for fd: protocol
On 07/26/2011 08:51 AM, Corey Bryant wrote:
+static int raw_open_fd(BlockDriverState *bs, const char *filename,
int flags)
+{
+ BDRVRawState *s = bs->opaque;
+ const char *fd_str;
+ int fd;
+
+ /* extract the file descriptor - fail if it's not fd: */
+ if (!strstart(filename, "fd:",&fd_str)) {
+ return -EINVAL;
+ }
+
+ if (!qemu_isdigit(fd_str[0])) {
+ /* get fd from monitor */
+ fd = qemu_get_fd(fd_str);
+ if (fd == -1) {
+ return -EBADF;
+ }
+ } else {
+ char *endptr = NULL;
+
+ fd = strtol(fd_str,&endptr, 10);
+ if (*endptr || (fd == 0&& fd_str == endptr)) {
+ return -EBADF;
+ }
+ }
+
+ s->fd = fd;
+ s->type = FTYPE_FILE;
+
+ return raw_open_common(bs, filename, flags, 0);
+}
+
+static BlockDriver bdrv_file_fd = {
+ .format_name = "file",
+ .protocol_name = "fd",
+ .instance_size = sizeof(BDRVRawState),
+ .bdrv_probe = NULL, /* no probe for protocols */
+ .bdrv_file_open = raw_open_fd,
+ .bdrv_read = raw_read,
+ .bdrv_write = raw_write,
+ .bdrv_close = raw_close,
+ .bdrv_flush = raw_flush,
+ .bdrv_discard = raw_discard,
+
+ .bdrv_aio_readv = raw_aio_readv,
+ .bdrv_aio_writev = raw_aio_writev,
+ .bdrv_aio_flush = raw_aio_flush,
+
+ .bdrv_truncate = raw_truncate,
+ .bdrv_getlength = raw_getlength,
+
+ .create_options = raw_create_options,
+};
+
I'm a bit unsure of how to support CD-ROM with the fd: protocol.
I don't think use of bdrv_file_fd is an option. For example, while
raw_open_fd may work, there is no eject support.
Another approach is to have 2 BlockDriver structs that support the fd
protocol. For example, creating a new BlockDriver struct that mirrors
bdrv_host_cdrom. So you would have bdrv_host_cdrom_fd with a
corresponding cdrom_open_fd function. But that doesn't appear possible
as it appears that the protocol must be unique among all BlockDriver
structs.
Do we need to introduce a similar protocol (maybe "cdfd") to support
passing of CD-ROM file descriptors?