[PATCH v2 3/4] rpmsg: char: Add possibility to use default endpoint of the rpmsg device.

Arnaud Pouliquen
2021-06-23T15:08:23Z

Current implementation create/destroy a new endpoint on each
rpmsg_eptdev_open/rpmsg_eptdev_release calls.

For a rpmsg device created by the NS announcement mechanism we need to
use a unique static endpoint that is the default rpmsg device endpoint
associated to the channel.

This patch prepares the introduction of a rpmsg channel device for the
char device. The rpmsg channel device will require a default endpoint to
communicate to the remote processor.

Add the static_ept field in rpmsg_eptdev structure. This boolean
determines the behavior on rpmsg_eptdev_open and rpmsg_eptdev_release call.

- If static_ept == false:
Use the legacy behavior by creating a new endpoint each time
rpmsg_eptdev_open is called and release it when rpmsg_eptdev_release
is called on /dev/rpmsgX device open/close.

- If static_ept == true:
use the rpmsg device default endpoint for the communication.
- Address the update of _rpmsg_chrdev_eptdev_create in e separate patch for readability.

Add protection in rpmsg_eptdev_ioctl to prevent to destroy a default endpoint.

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
---
update vs V1:
- remove the management of the default endpoint creation from rpmsg_eptdev_open.

---
drivers/rpmsg/rpmsg_char.c | 21 +++++++++++++++++++--
1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
index 50b7d4b00175..a75dce1e29d8 100644
--- a/drivers/rpmsg/rpmsg_char.c
+++ b/drivers/rpmsg/rpmsg_char.c
@@ -45,6 +45,8 @@ static DEFINE_IDA(rpmsg_minor_ida);
* @queue_lock: synchronization of @queue operations
* @queue: incoming message queue
* @readq: wait object for incoming queue
+ * @static_ept: specify if the endpoint has to be created at each device opening or
+ * if the default endpoint should be used.
*/
struct rpmsg_eptdev {
struct device dev;
@@ -59,6 +61,8 @@ struct rpmsg_eptdev {
spinlock_t queue_lock;
struct sk_buff_head queue;
wait_queue_head_t readq;
+
+ bool static_ept;
};

int rpmsg_chrdev_eptdev_destroy(struct device *dev, void *data)
@@ -116,7 +120,15 @@ static int rpmsg_eptdev_open(struct inode *inode, struct file *filp)

get_device(dev);

- ept = rpmsg_create_ept(rpdev, rpmsg_ept_cb, eptdev, eptdev->chinfo);
+ /*
+ * If the static_ept is set to true, the rpmsg device default endpoint is used.
+ * Else a new endpoint is created on open that will be destroyed on release.
+ */
+ if (eptdev->static_ept)
+ ept = rpdev->ept;
+ else
+ ept = rpmsg_create_ept(rpdev, rpmsg_ept_cb, eptdev, eptdev->chinfo);
+
if (!ept) {
dev_err(dev, "failed to open %s\n", eptdev->chinfo.name);
put_device(dev);
@@ -137,7 +149,8 @@ static int rpmsg_eptdev_release(struct inode *inode, struct file *filp)
/* Close the endpoint, if it's not already destroyed by the parent */
mutex_lock(&eptdev->ept_lock);
if (eptdev->ept) {
- rpmsg_destroy_ept(eptdev->ept);
+ if (!eptdev->static_ept)
+ rpmsg_destroy_ept(eptdev->ept);
eptdev->ept = NULL;
}
mutex_unlock(&eptdev->ept_lock);
@@ -264,6 +277,10 @@ static long rpmsg_eptdev_ioctl(struct file *fp, unsigned int cmd,
if (cmd != RPMSG_DESTROY_EPT_IOCTL)
return -EINVAL;

+ /* Don't allow to destroy a default endpoint. */
+ if (!eptdev->rpdev || eptdev->ept == eptdev->rpdev->ept)
+ return -EPERM;
+
return rpmsg_chrdev_eptdev_destroy(&eptdev->dev, NULL);
}

--
2.17.1