cxl/mbox: Use new return_code handling

Use the global cxl_mbox_cmd_rc table to improve debug messaging
in __cxl_pci_mbox_send_cmd() and allow cxl_mbox_send_cmd()
to map to proper kernel style errno codes - this patch
continues to use -ENXIO only so no change in semantics.
Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Reviewed by: Adam Manzanares <a.manzanares@samsung.com>
Link: https://lore.kernel.org/r/20220404021216.66841-5-dave@stgolabs.netSigned-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/cxl/core/mbox.c

@@ -180,9 +180,8 @@ int cxl_mbox_send_cmd(struct cxl_dev_state *cxlds, u16 opcode, void *in,
 	if (rc)
 		return rc;
 
-	/* TODO: Map return code to proper kernel style errno */
 	if (mbox_cmd.return_code != CXL_MBOX_CMD_RC_SUCCESS)
-		return -ENXIO;
+		return cxl_mbox_cmd_rc2errno(&mbox_cmd);
 
 	/*
 	 * Variable sized commands can't be validated and so it's up to the

drivers/cxl/pci.c

@@ -178,7 +178,8 @@ static int __cxl_pci_mbox_send_cmd(struct cxl_dev_state *cxlds,
 		FIELD_GET(CXLDEV_MBOX_STATUS_RET_CODE_MASK, status_reg);
 
 	if (mbox_cmd->return_code != CXL_MBOX_CMD_RC_SUCCESS) {
-		dev_dbg(dev, "Mailbox operation had an error\n");
+		dev_dbg(dev, "Mailbox operation had an error: %s\n",
+			cxl_mbox_cmd_rc2str(mbox_cmd));
 		return 0; /* completed but caller must check return_code */
 	}