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 2d86ac02b2cd53d6b0da948b7dab69d2bfe436c4..8463f83e037fb26599625bdddb0b1dd766c0018f 100644 (file)
--- a/drivers/hid/i2c-hid/i2c-hid.c
+++ b/drivers/hid/i2c-hid/i2c-hid.c
@@ -981,6 +981,14 @@ 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;