acpi/nfit: Fix bus command validation

Commit 11189c10 "acpi/nfit: Fix command-supported detection" broke
ND_CMD_CALL for bus-level commands. The "func = cmd" assumption is only
valid for:

    ND_CMD_ARS_CAP
    ND_CMD_ARS_START
    ND_CMD_ARS_STATUS
    ND_CMD_CLEAR_ERROR

The function number otherwise needs to be pulled from the command
payload for:

    NFIT_CMD_TRANSLATE_SPA
    NFIT_CMD_ARS_INJECT_SET
    NFIT_CMD_ARS_INJECT_CLEAR
    NFIT_CMD_ARS_INJECT_GET

Update cmd_to_func() for the bus case and call it in the common path.

Fixes: 11189c10 ("acpi/nfit: Fix command-supported detection")
Cc: <stable@vger.kernel.org>
Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>
Reported-by: Grzegorz Burzynski <grzegorz.burzynski@intel.com>
Tested-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/acpi/nfit/core.c

@@ -415,7 +415,7 @@ static int cmd_to_func(struct nfit_mem *nfit_mem, unsigned int cmd,
 	if (call_pkg) {
 		int i;
 
-		if (nfit_mem->family != call_pkg->nd_family)
+		if (nfit_mem && nfit_mem->family != call_pkg->nd_family)
 			return -ENOTTY;
 
 		for (i = 0; i < ARRAY_SIZE(call_pkg->nd_reserved2); i++)
@@ -424,6 +424,10 @@ static int cmd_to_func(struct nfit_mem *nfit_mem, unsigned int cmd,
 		return call_pkg->nd_command;
 	}
 
+	/* In the !call_pkg case, bus commands == bus functions */
+	if (!nfit_mem)
+		return cmd;
+
 	/* Linux ND commands == NVDIMM_FAMILY_INTEL function numbers */
 	if (nfit_mem->family == NVDIMM_FAMILY_INTEL)
 		return cmd;
@@ -454,17 +458,18 @@ int acpi_nfit_ctl(struct nvdimm_bus_descriptor *nd_desc, struct nvdimm *nvdimm,
 	if (cmd_rc)
 		*cmd_rc = -EINVAL;
 
+	if (cmd == ND_CMD_CALL)
+		call_pkg = buf;
+	func = cmd_to_func(nfit_mem, cmd, call_pkg);
+	if (func < 0)
+		return func;
+
 	if (nvdimm) {
 		struct acpi_device *adev = nfit_mem->adev;
 
 		if (!adev)
 			return -ENOTTY;
 
-		if (cmd == ND_CMD_CALL)
-			call_pkg = buf;
-		func = cmd_to_func(nfit_mem, cmd, call_pkg);
-		if (func < 0)
-			return func;
 		dimm_name = nvdimm_name(nvdimm);
 		cmd_name = nvdimm_cmd_name(cmd);
 		cmd_mask = nvdimm_cmd_mask(nvdimm);
@@ -475,11 +480,8 @@ int acpi_nfit_ctl(struct nvdimm_bus_descriptor *nd_desc, struct nvdimm *nvdimm,
 	} else {
 		struct acpi_device *adev = to_acpi_dev(acpi_desc);
 
-		func = cmd;
 		cmd_name = nvdimm_bus_cmd_name(cmd);
 		cmd_mask = nd_desc->cmd_mask;
-		dsm_mask = cmd_mask;
-		if (cmd == ND_CMD_CALL)
 		dsm_mask = nd_desc->bus_dsm_mask;
 		desc = nd_cmd_bus_desc(cmd);
 		guid = to_nfit_uuid(NFIT_DEV_BUS);