dmi scan: warn about too early calls to dmi_check_system()

It happened to me recently that i added a dmi_check_system() quirk
in a too early codepath, and it was silently ignored because all the
DMI tables and strings were still empty.

As this situation is clearly a programming error / kernel bug,
warn when it happens, instead of silently ignoring quirks.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

drivers/firmware/dmi_scan.c

@@ -15,6 +15,11 @@
  */
 static char dmi_empty_string[] = "        ";
 
+/*
+ * Catch too early calls to dmi_check_system():
+ */
+static int dmi_initialized;
+
 static const char * __init dmi_string_nosave(const struct dmi_header *dm, u8 s)
 {
 	const u8 *bp = ((u8 *) dm) + dm->length;
@@ -366,21 +371,21 @@ void __init dmi_scan_machine(void)
 
 	if (efi_enabled) {
 		if (efi.smbios == EFI_INVALID_TABLE_ADDR)
-			goto out;
+			goto error;
 
 		/* This is called as a core_initcall() because it isn't
 		 * needed during early boot.  This also means we can
 		 * iounmap the space when we're done with it.
 		 */
 		p = dmi_ioremap(efi.smbios, 32);
 		if (p == NULL)
-			goto out;
+			goto error;
 
 		rc = dmi_present(p + 0x10); /* offset of _DMI_ string */
 		dmi_iounmap(p, 32);
 		if (!rc) {
 			dmi_available = 1;
-			return;
+			goto out;
 		}
 	}
 	else {
@@ -391,19 +396,22 @@ void __init dmi_scan_machine(void)
 		 */
 		p = dmi_ioremap(0xF0000, 0x10000);
 		if (p == NULL)
-			goto out;
+			goto error;
 
 		for (q = p; q < p + 0x10000; q += 16) {
 			rc = dmi_present(q);
 			if (!rc) {
 				dmi_available = 1;
 				dmi_iounmap(p, 0x10000);
-				return;
+				goto out;
 			}
 		}
 		dmi_iounmap(p, 0x10000);
 	}
- out:	printk(KERN_INFO "DMI not present or invalid.\n");
+ error:
+	printk(KERN_INFO "DMI not present or invalid.\n");
+ out:
+	dmi_initialized = 1;
 }
 
 /**
@@ -424,6 +432,8 @@ int dmi_check_system(const struct dmi_system_id *list)
 	int i, count = 0;
 	const struct dmi_system_id *d = list;
 
+	WARN(!dmi_initialized, KERN_ERR "dmi check: not initialized yet.\n");
+
 	while (d->ident) {
 		for (i = 0; i < ARRAY_SIZE(d->matches); i++) {
 			int s = d->matches[i].slot;