On 09/05/2020 04:24, Wen Yang wrote:
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().
For an KOBJ_ADD you'd return an error.
grep -r "= kobject_uevent(" *
drivers/misc/cxl/sysfs.c: rc = kobject_uevent(&cr->kobj, KOBJ_ADD);
drivers/uio/uio.c: ret = kobject_uevent(&map->kobj, KOBJ_ADD);
drivers/uio/uio.c: ret = kobject_uevent(&portio->kobj, KOBJ_ADD);
drivers/visorbus/visorchipset.c: res =
kobject_uevent(&chipset_dev->acpi_device->dev.kobj, KOBJ_ONLINE);
drivers/visorbus/visorchipset.c: int res =
kobject_uevent(&chipset_dev->acpi_device->dev.kobj,
For a KOBJ_CHANGE I guess we could print an error
if (kobject_uevent(&sw->dev.kobj, KOBJ_CHANGE)
dev_err(&sw->dev, "failed to signal USB role-switch uevent\n");
Nobody else seems that bothered about it.
grep -r "if (kobject_uevent(" *
Should we move it under the line mutex_unlock(&sw->lock)?
I think probably not. the mutex serializes the notification. In theory
outside the mutex you could get an out-of-order notification.
The main reason I put it where it is, is we already test ret and should
only notify the change, when the role-switch has suceeded.
As I say, in theory anyway, the mutex enforces the signalling, whatever
about the reception, of the role-switch change, so IMO inside the bounds
of the mutex is the right place to put it.
---
bod
