Re: [PATCH] usb: roles: Switch on role-switch uevent reporting

From: Wen Yang
Date: Fri May 08 2020 - 23:24:18 EST




在 2020/5/9 上午12:29, Bryan O'Donoghue 写道:
Right now we don't report to user-space a role switch when doing a
usb_role_switch_set_role() despite having registered the uevent callbacks.

This patch switches on the notifications allowing user-space to see
role-switch change notifications and subsequently determine the current
controller data-role.

example:
PFX=/devices/platform/soc/78d9000.usb/ci_hdrc.0

root@somebox# udevadm monitor -p

KERNEL[49.894994] change $PFX/usb_role/ci_hdrc.0-role-switch (usb_role)
ACTION=change
DEVPATH=$PFX/usb_role/ci_hdrc.0-role-switch
SUBSYSTEM=usb_role
DEVTYPE=usb_role_switch
USB_ROLE_SWITCH=ci_hdrc.0-role-switch
SEQNUM=2432

Cc: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Chunfeng Yun <chunfeng.yun@xxxxxxxxxxxx>
Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Cc: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>
Cc: Wen Yang <wenyang@xxxxxxxxxxxxxxxxx>
Cc: chenqiwu <chenqiwu@xxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@xxxxxxxxxx>
---
drivers/usb/roles/class.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/roles/class.c b/drivers/usb/roles/class.c
index 5b17709821df..27d92af29635 100644
--- a/drivers/usb/roles/class.c
+++ b/drivers/usb/roles/class.c
@@ -49,8 +49,10 @@ int usb_role_switch_set_role(struct usb_role_switch *sw, enum usb_role role)
mutex_lock(&sw->lock);
ret = sw->set(sw, role);
- if (!ret)
+ if (!ret) {
sw->role = role;
+ kobject_uevent(&sw->dev.kobj, KOBJ_CHANGE);
+ }
mutex_unlock(&sw->lock);


Hi, we may also need to deal with the return value of kobject_uevent(). Should we move it under the line mutex_unlock(&sw->lock)?

Regards,
Wen