[PATCH] HID: hyperv: streamline driver probe to avoid devres issues

[Vitaly Kuznetsov <vkuznets@redhat.com>]

It was found that unloading 'hid_hyperv' module results in a devres
complaint:

 ...
 hv_vmbus: unregistering driver hid_hyperv
 ------------[ cut here ]------------
 WARNING: CPU: 2 PID: 3983 at drivers/base/devres.c:691 devres_release_group+0x1f2/0x2c0
 ...
 Call Trace:
  <TASK>
  ? devres_release_group+0x1f2/0x2c0
  ? __warn+0xd1/0x1c0
  ? devres_release_group+0x1f2/0x2c0
  ? report_bug+0x32a/0x3c0
  ? handle_bug+0x53/0xa0
  ? exc_invalid_op+0x18/0x50
  ? asm_exc_invalid_op+0x1a/0x20
  ? devres_release_group+0x1f2/0x2c0
  ? devres_release_group+0x90/0x2c0
  ? rcu_is_watching+0x15/0xb0
  ? __pfx_devres_release_group+0x10/0x10
  hid_device_remove+0xf5/0x220
  device_release_driver_internal+0x371/0x540
  ? klist_put+0xf3/0x170
  bus_remove_device+0x1f1/0x3f0
  device_del+0x33f/0x8c0
  ? __pfx_device_del+0x10/0x10
  ? cleanup_srcu_struct+0x337/0x500
  hid_destroy_device+0xc8/0x130
  mousevsc_remove+0xd2/0x1d0 [hid_hyperv]
  device_release_driver_internal+0x371/0x540
  driver_detach+0xc5/0x180
  bus_remove_driver+0x11e/0x2a0
  ? __mutex_unlock_slowpath+0x160/0x5e0
  vmbus_driver_unregister+0x62/0x2b0 [hv_vmbus]
  ...

And the issue seems to be that the corresponding devres group is not
allocated. Normally, devres_open_group() is called from
__hid_device_probe() but Hyper-V HID driver overrides 'hid_dev->driver'
with 'mousevsc_hid_driver' stub and basically re-implements
__hid_device_probe() by calling hid_parse() and hid_hw_start() but not
devres_open_group(). hid_device_probe() does not call __hid_device_probe()
for it. Later, when the driver is removed, hid_device_remove() calls
devres_release_group() as it doesn't check whether hdev->driver was
initially overridden or not.

The issue seems to be related to the commit 62c68e7cee33 ("HID: ensure
timely release of driver-allocated resources") but the commit itself seems
to be correct.

Fix the issue by dropping the 'hid_dev->driver' override and the
now unneeded hid_parse()/hid_hw_start() calls. One notable difference of
the change is hid_hw_start() is now called with HID_CONNECT_DEFAULT which
implies HID_CONNECT_HIDRAW. This doesn't seem to cause any immediate issues
but 'HID_CONNECT_HIDINPUT | HID_CONNECT_HIDDEV' combo was used in the
driver for a long time and it is unclear whether hidraw was excluded on
purpose or not.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 drivers/hid/hid-hyperv.c | 17 -----------------
 1 file changed, 17 deletions(-)

diff --git a/drivers/hid/hid-hyperv.c b/drivers/hid/hid-hyperv.c
index f33485d83d24..1609a56ffa7c 100644
--- a/drivers/hid/hid-hyperv.c
+++ b/drivers/hid/hid-hyperv.c
@@ -431,8 +431,6 @@ static const struct hid_ll_driver mousevsc_ll_driver = {
 	.raw_request = mousevsc_hid_raw_request,
 };
 
-static struct hid_driver mousevsc_hid_driver;
-
 static int mousevsc_probe(struct hv_device *device,
 			const struct hv_vmbus_device_id *dev_id)
 {
@@ -473,7 +471,6 @@ static int mousevsc_probe(struct hv_device *device,
 	}
 
 	hid_dev->ll_driver = &mousevsc_ll_driver;
-	hid_dev->driver = &mousevsc_hid_driver;
 	hid_dev->bus = BUS_VIRTUAL;
 	hid_dev->vendor = input_dev->hid_dev_info.vendor;
 	hid_dev->product = input_dev->hid_dev_info.product;
@@ -488,20 +485,6 @@ static int mousevsc_probe(struct hv_device *device,
 	if (ret)
 		goto probe_err2;
 
-
-	ret = hid_parse(hid_dev);
-	if (ret) {
-		hid_err(hid_dev, "parse failed\n");
-		goto probe_err2;
-	}
-
-	ret = hid_hw_start(hid_dev, HID_CONNECT_HIDINPUT | HID_CONNECT_HIDDEV);
-
-	if (ret) {
-		hid_err(hid_dev, "hw start failed\n");
-		goto probe_err2;
-	}
-
 	device_init_wakeup(&device->device, true);
 
 	input_dev->connected = true;
-- 
2.47.0