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    SubjectRe: [PATCH] usb: roles: Switch on role-switch uevent reporting
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    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@linux.intel.com>
    > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    > Cc: Chunfeng Yun <chunfeng.yun@mediatek.com>
    > Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
    > Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
    > Cc: Wen Yang <wenyang@linux.alibaba.com>
    > Cc: chenqiwu <chenqiwu@xiaomi.com>
    > Cc: linux-kernel@vger.kernel.org
    > Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
    > ---
    > 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

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