rtc: efi: Fail probing if RTC reads don't work

While the EFI spec mandates an RTC, not every implementation actually adheres to that rule (or can adhere to it - some systems just don't have an RTC). For those, we really don't want to probe the EFI RTC driver at all, because if we do we'd get a non-functional driver that does nothing useful but only spills our kernel log with warnings. Signed-off-by: Alexander Graf <[email protected]> Acked-by: Ard Biesheuvel <[email protected]> Signed-off-by: Alexandre Belloni <[email protected]>
lachaves · Jun 6, 2016 · 7368c69 · 7368c69
1 parent 06776c8
commit 7368c69
Showing 1 changed file with 6 additions and 0 deletions.
diff --git a/drivers/rtc/rtc-efi.c b/drivers/rtc/rtc-efi.c
@@ -259,6 +259,12 @@ static const struct rtc_class_ops efi_rtc_ops = {
 static int __init efi_rtc_probe(struct platform_device *dev)
 {
 	struct rtc_device *rtc;
+	efi_time_t eft;
+	efi_time_cap_t cap;
+
+	/* First check if the RTC is usable */
+	if (efi.get_time(&eft, &cap) != EFI_SUCCESS)
+		return -ENODEV;
 
 	rtc = devm_rtc_device_register(&dev->dev, "rtc-efi", &efi_rtc_ops,
 					THIS_MODULE);