[lvc-project] [PATCH v4 2/4] HID: roccat: use device_is_registered() to check whether device is available

[Dmitry Antipov]

Introduce roccat_device_available() to check whether device
is actually available (i.e. not disconnected), thus removing
explicit 'exist' flag from 'struct roccat_device'.

Signed-off-by: Dmitry Antipov <dmantipov at yandex.ru>
---
v4: use READ_ONCE() and WRITE_ONCE() for device access
v3: initial version to join the series
---
 drivers/hid/hid-roccat.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/hid/hid-roccat.c b/drivers/hid/hid-roccat.c
index 5deb6da8d4f7..96aa508111a1 100644
--- a/drivers/hid/hid-roccat.c
+++ b/drivers/hid/hid-roccat.c
@@ -40,7 +40,6 @@ struct roccat_device {
 	unsigned int minor;
 	int report_size;
 	int open;
-	int exist;
 	wait_queue_head_t wait;
 	struct device *dev;
 	struct hid_device *hid;
@@ -70,6 +69,13 @@ static struct roccat_device *devices[ROCCAT_MAX_DEVICES];
 /* protects modifications of devices array */
 static DEFINE_MUTEX(devices_lock);
 
+static bool roccat_device_available(struct roccat_device *device)
+{
+	struct device *dev = READ_ONCE(device->dev);
+
+	return dev ? device_is_registered(dev) : false;
+}
+
 static void roccat_free_device(struct roccat_device *device)
 {
 	int i;
@@ -105,7 +111,7 @@ static ssize_t roccat_read(struct file *file, char __user *buffer,
 				retval = -ERESTARTSYS;
 				break;
 			}
-			if (!device->exist) {
+			if (!roccat_device_available(device)) {
 				retval = -EIO;
 				break;
 			}
@@ -149,7 +155,7 @@ static __poll_t roccat_poll(struct file *file, poll_table *wait)
 	poll_wait(file, &reader->device->wait, wait);
 	if (reader->cbuf_start != reader->device->cbuf_end)
 		return EPOLLIN | EPOLLRDNORM;
-	if (!reader->device->exist)
+	if (!roccat_device_available(reader->device))
 		return EPOLLERR | EPOLLHUP;
 	return 0;
 }
@@ -231,7 +237,7 @@ static int roccat_release(struct inode *inode, struct file *file)
 
 	if (!--device->open) {
 		/* removing last reader */
-		if (device->exist) {
+		if (roccat_device_available(device)) {
 			hid_hw_power(device->hid, PM_HINT_NORMAL);
 			hid_hw_close(device->hid);
 		} else {
@@ -350,7 +356,6 @@ int roccat_connect(const struct class *klass, struct hid_device *hid, int report
 	mutex_init(&device->cbuf_lock);
 	device->minor = minor;
 	device->hid = hid;
-	device->exist = 1;
 	device->cbuf_end = 0;
 	device->report_size = report_size;
 
@@ -369,10 +374,8 @@ void roccat_disconnect(int minor)
 	mutex_lock(&devices_lock);
 	device = devices[minor];
 
-	device->exist = 0; /* TODO exist maybe not needed */
-
 	device_destroy(device->dev->class, MKDEV(roccat_major, minor));
-
+	WRITE_ONCE(device->dev, NULL);
 	devices[minor] = NULL;
 
 	if (device->open) {
-- 
2.55.0