Re: [PATCH] HID: logitech-dj: issue udev change event on device connection
From: Mario Limonciello <hidden>
Date: 2020-03-18 17:15:28
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On Wed, Mar 18, 2020 at 11:19 AM Filipe Laíns [off-list ref] wrote:
quoted hunk ↗ jump to hunk
As discussed in the mailing list:quoted
Right now the hid-logitech-dj driver will export one node for each connected device, even when the device is not connected. That causes some trouble because in userspace we don't have have any way to know if the device is connected or not, so when we try to communicate, if the device is disconnected it will fail.The solution reached to solve this issue is to trigger an udev change event when the device connects, this way userspace can just wait on those connections instead of trying to ping the device. Signed-off-by: Filipe Laíns <redacted> --- drivers/hid/hid-logitech-dj.c | 2 ++ 1 file changed, 2 insertions(+)diff --git a/drivers/hid/hid-logitech-dj.c b/drivers/hid/hid-logitech-dj.c index 48dff5d6b605..fcd481a0be1f 100644 --- a/drivers/hid/hid-logitech-dj.c +++ b/drivers/hid/hid-logitech-dj.c@@ -1464,6 +1464,8 @@ static int logi_dj_dj_event(struct hid_device *hdev, if (dj_report->report_params[CONNECTION_STATUS_PARAM_STATUS] == STATUS_LINKLOSS) { logi_dj_recv_forward_null_report(djrcv_dev, dj_report); + } else { + kobject_uevent(&hdev->dev.kobj, KOBJ_CHANGE); } break; default: --2.25.1
The problem that will remain here is the transition period for userspace to start to rely upon this. It will have no idea whether the kernel is expected to send events or not. What do you think about adding a syfs attribute to indicate that events are being sent? Or something similar?