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

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Message-Id: <20200508162937.2566818-1-bryan.odonoghue@linaro.org>
Date:   Fri,  8 May 2020 17:29:37 +0100
From:   Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To:     heikki.krogerus@...ux.intel.com, gregkh@...uxfoundation.org,
        linux-usb@...r.kernel.org, bryan.odonoghue@...aro.org
Cc:     Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Wen Yang <wenyang@...ux.alibaba.com>,
        chenqiwu <chenqiwu@...omi.com>, linux-kernel@...r.kernel.org
Subject: [PATCH] usb: roles: Switch on role-switch uevent reporting

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@...ebox# 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@...ux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Chunfeng Yun <chunfeng.yun@...iatek.com>
Cc: Suzuki K Poulose <suzuki.poulose@....com>
Cc: Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc: Wen Yang <wenyang@...ux.alibaba.com>
Cc: chenqiwu <chenqiwu@...omi.com>
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@...aro.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);
 
-- 
2.25.1