HID: i2c-hid: check if device is there before really probing

[ Upstream commit b3a81b6c4fc6730ac49e20d789a93c0faabafc98 ]

On many Chromebooks touch devices are multi-sourced; the components are
electrically compatible and one can be freely swapped for another without
changing the OS image or firmware.

To avoid bunch of scary messages when device is not actually present in the
system let's try testing basic communication with it and if there is no
response terminate probe early with -ENXIO.

Signed-off-by: Dmitry Torokhov <dtor@chromium.org>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c
index a5fed668fde11f708a9adaa8ac8b9f75a068544a..4248d253c32adec48c1cfcb9647ac1bf93e5ab8d 100644 (file)
--- a/drivers/hid/i2c-hid/i2c-hid.c
+++ b/drivers/hid/i2c-hid/i2c-hid.c
@@ -1017,6 +1017,14 @@ static int i2c_hid_probe(struct i2c_client *client,
        pm_runtime_set_active(&client->dev);
        pm_runtime_enable(&client->dev);
 
+       /* Make sure there is something at this address */
+       ret = i2c_smbus_read_byte(client);
+       if (ret < 0) {
+               dev_dbg(&client->dev, "nothing at this address: %d\n", ret);
+               ret = -ENXIO;
+               goto err_pm;
+       }
+
        ret = i2c_hid_fetch_hid_descriptor(ihid);
        if (ret < 0)
                goto err_pm;