Re: [PATCH v2] hwmon: corsair-cpro: fix ccp_probe, add delay [HID related]

On 8/18/20 6:12 AM, Marius Zachmann wrote:

On 18.08.20 at 17:35:33 CEST, Guenter Roeck wrote

quoted

On Mon, Aug 17, 2020 at 09:00:40AM +0200, Marius Zachmann wrote:

quoted

Possibly because of the changes in usbhid/hid-core.c the first
raw input report is not received during ccp_probe function and it will
timeout. I am not sure, whether this behaviour is expected after
hid_device_io_start or if I am missing something.
As a solution this adds msleep(50) to ccp_probe so that all initial
input reports can be received.

Signed-off-by: Marius Zachmann <mail@mariuszachmann.de>

Let's just ask the HID maintainers. Is this expected, and the correct fix ?

Thanks,
Guenter

This seems to be a problem with "HID: usbhid: do not sleep when opening
device". There is a bug report with some Logitech devices at the correct
thread. These drivers also use hid_device_io_start and fail. Seems to me,
this is the same problem and I retract this (not so beautiful) fix until
this is sorted out.

I even was involved in that patch. Sigh.

Guenter

Thanks,
Marius

quoted

quoted

---
v2:
- fix accidentally deleted comment

---
 drivers/hwmon/corsair-cpro.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/hwmon/corsair-cpro.c b/drivers/hwmon/corsair-cpro.c
index 591929ec217a..c04fac1d820f 100644
--- a/drivers/hwmon/corsair-cpro.c
+++ b/drivers/hwmon/corsair-cpro.c

@@ -10,6 +10,7 @@

 #include <linux/bitops.h>
 #include <linux/completion.h>
+#include <linux/delay.h>
 #include <linux/hid.h>
 #include <linux/hwmon.h>
 #include <linux/kernel.h>

@@ -513,6 +514,7 @@ static int ccp_probe(struct hid_device *hdev, const struct hid_device_id *id)
 	init_completion(&ccp->wait_input_report);

 	hid_device_io_start(hdev);
+	msleep(50); /* wait before events can be received */

 	/* temp and fan connection status only updates when device is powered on */
 	ret = get_temp_cnct(ccp);
--

2.28.0