HID: mcp2221: Allow IO to start during probe

During the probe we add an I2C adapter and as soon as we add that adapter
it may be used for a transfer (e.g via the code in i2cdetect()).
Those transfers are not able to complete and time out. This is because the
HID raw_event callback (mcp2221_raw_event) will not be invoked until the
HID device's 'driver_input_lock' is marked up at the completion of the
probe in hid_device_probe(). This starves the driver of the responses it
is waiting for.
In order to allow the I2C transfers to complete while we are still in the
probe, start the IO once we have completed init of the HID device.

This issue seems to have been seen before and a patch was submitted but
it seems it was never accepted. See:
https://lore.kernel.org/all/20221103222714.21566-3-Enrik.Berkhan@inka.de/

Signed-off-by: Hamish Martin <hamish.martin@alliedtelesis.co.nz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

diff --git a/drivers/hid/hid-mcp2221.c b/drivers/hid/hid-mcp2221.c
index b95f31c..aef0785 100644 (file)
--- a/drivers/hid/hid-mcp2221.c
+++ b/drivers/hid/hid-mcp2221.c
@@ -1142,6 +1142,8 @@ static int mcp2221_probe(struct hid_device *hdev,
        if (ret)
                return ret;
 
+       hid_device_io_start(hdev);
+
        /* Set I2C bus clock diviser */
        if (i2c_clk_freq > 400)
                i2c_clk_freq = 400;