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

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>

diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c
index cf71c33ac2b2fac8b23a308979e00c8668476e57..c5ad918e36e311c3a5f38eabf90f8df9262c4d85 100644 (file)
--- a/drivers/hid/i2c-hid/i2c-hid.c
+++ b/drivers/hid/i2c-hid/i2c-hid.c
@@ -1060,6 +1060,14 @@ static int i2c_hid_probe(struct i2c_client *client,
        pm_runtime_enable(&client->dev);
        device_enable_async_suspend(&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;