Add -s "help" and -l "help" to print a list of supported PCI and LPC devices.

For tools that uses bhyve such like libvirt, it is important to be able to
probe what features are supported by the given bhyve binary.

To give more context, libvirt probes bhyve's capabilities in a not very
effective way:
- Running 'bhyve -h' and parsing output.
- To detect devices, it runs 'bhyve -s 0,dev' for every each device and
  parses error output to identify if the device is supported or not.

PR:		2101111
Submitted by:	novel
MFC after:	2 weeks
Relnotes:	yes
Sponsored by:	iXsystems Inc.

usr.sbin/bhyve/bhyverun.c

@@ -960,13 +960,19 @@ main(int argc, char *argv[])
 			gdb_port = atoi(optarg);
 			break;
 		case 'l':
-			if (lpc_device_parse(optarg) != 0) {
+			if (strncmp(optarg, "help", strlen(optarg)) == 0) {
+				lpc_print_supported_devices();
+				exit(0);
+			} else if (lpc_device_parse(optarg) != 0) {
 				errx(EX_USAGE, "invalid lpc device "
 				    "configuration '%s'", optarg);
 			}
 			break;
 		case 's':
-			if (pci_parse_slot(optarg) != 0)
+			if (strncmp(optarg, "help", strlen(optarg)) == 0) {
+				pci_print_supported_devices();
+				exit(0);
+			} else if (pci_parse_slot(optarg) != 0)
 				exit(4);
 			else
 				break;

usr.sbin/bhyve/pci_emul.c

@@ -237,6 +237,17 @@ done:
 	return (error);
 }
 
+void
+pci_print_supported_devices()
+{
+	struct pci_devemu **pdpp, *pdp;
+
+	SET_FOREACH(pdpp, pci_devemu_set) {
+		pdp = *pdpp;
+		printf("%s\n", pdp->pe_emu);
+	}
+}
+
 static int
 pci_valid_pba_offset(struct pci_devinst *pi, uint64_t offset)
 {

usr.sbin/bhyve/pci_emul.h

@@ -234,6 +234,7 @@ int	pci_msix_table_bar(struct pci_devinst *pi);
 int	pci_msix_pba_bar(struct pci_devinst *pi);
 int	pci_msi_maxmsgnum(struct pci_devinst *pi);
 int	pci_parse_slot(char *opt);
+void    pci_print_supported_devices();
 void	pci_populate_msicap(struct msicap *cap, int msgs, int nextptr);
 int	pci_emul_add_msixcap(struct pci_devinst *pi, int msgnum, int barnum);
 int	pci_emul_msix_twrite(struct pci_devinst *pi, uint64_t offset, int size,

usr.sbin/bhyve/pci_lpc.c

@@ -114,6 +114,16 @@ done:
 	return (error);
 }
 
+void
+lpc_print_supported_devices()
+{
+	size_t i;
+
+	printf("bootrom\n");
+	for (i = 0; i < LPC_UART_NUM; i++)
+		printf("%s\n", lpc_uart_names[i]);
+}
+
 const char *
 lpc_bootrom(void)
 {

usr.sbin/bhyve/pci_lpc.h

@@ -68,6 +68,7 @@ struct lpc_sysres {
 #define	SYSRES_MEM(base, length)	LPC_SYSRES(LPC_SYSRES_MEM, base, length)
 
 int	lpc_device_parse(const char *opt);
+void    lpc_print_supported_devices();
 char	*lpc_pirq_name(int pin);
 void	lpc_pirq_routed(void);
 const char *lpc_bootrom(void);