bq27000: report missing device better.

One an hdq buss, a missing device reads as 0xff, not -1.
So do a translation to allow detecting of a missing bus.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Sebastian Reichel <sre@kernel.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/power/bq27x00_battery.c b/drivers/power/bq27x00_battery.c
index a0f205b0471d..e10763e3a1d5 100644
--- a/drivers/power/bq27x00_battery.c
+++ b/drivers/power/bq27x00_battery.c
@@ -416,6 +416,9 @@ static void bq27x00_update(struct bq27x00_device_info *di)
         bool is_bq27425 = di->chip == BQ27425;
 
         cache.flags = bq27x00_read(di, BQ27x00_REG_FLAGS, !is_bq27500);
+        if ((cache.flags & 0xff) == 0xff)
+                /* read error */
+                cache.flags = -1;
         if (cache.flags >= 0) {
                 if (!is_bq27500 && !is_bq27425
                                 && (cache.flags & BQ27000_FLAG_CI)) {