thunderbolt: Do not try to read UID if DROM offset is read as 0

At least Falcon Ridge when in host mode does not have any kind of DROM
available and reading DROM offset returns 0 for these. Do not try to
read DROM any further in that case.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Yehezkel Bernat <yehezkel.bernat@intel.com>
Reviewed-by: Michael Jamet <michael.jamet@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Andreas Noever <andreas.noever@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/thunderbolt/eeprom.c b/drivers/thunderbolt/eeprom.c
index 6392990c984dd1ca462219b70e515a5d75aca9af..e4e64b130514891707408c65d5ac068341e931cb 100644 (file)
--- a/drivers/thunderbolt/eeprom.c
+++ b/drivers/thunderbolt/eeprom.c
@@ -276,6 +276,9 @@ int tb_drom_read_uid_only(struct tb_switch *sw, u64 *uid)
        if (res)
                return res;
 
+       if (drom_offset == 0)
+               return -ENODEV;
+
        /* read uid */
        res = tb_eeprom_read_n(sw, drom_offset, data, 9);
        if (res)