[PATCH V4 3/3] rpmsg: char: Add TIOCMGET/TIOCMSET ioctl support

From: Sarannya S
Date: Mon Nov 28 2022 - 08:30:14 EST


Add TICOMGET and TIOCMSET ioctl support for rpmsg char device nodes
to get/set the low level transport signals.

Signed-off-by: Chris Lew <quic_clew@xxxxxxxxxxx>
Signed-off-by: Deepak Kumar Singh <quic_deesin@xxxxxxxxxxx>
Signed-off-by: Sarannya S <quic_sarannya@xxxxxxxxxxx>
---
drivers/rpmsg/rpmsg_char.c | 60 +++++++++++++++++++++++++++++++++++++++-------
1 file changed, 52 insertions(+), 8 deletions(-)

diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
index 3e0b8f3..d44c8a6 100644
--- a/drivers/rpmsg/rpmsg_char.c
+++ b/drivers/rpmsg/rpmsg_char.c
@@ -23,6 +23,7 @@
#include <linux/rpmsg.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
+#include <linux/termios.h>
#include <linux/uaccess.h>
#include <uapi/linux/rpmsg.h>

@@ -68,6 +69,8 @@ struct rpmsg_eptdev {
struct sk_buff_head queue;
wait_queue_head_t readq;

+ u32 remote_signals;
+ bool signals_pending;
};

int rpmsg_chrdev_eptdev_destroy(struct device *dev, void *data)
@@ -109,7 +112,22 @@ static int rpmsg_ept_cb(struct rpmsg_device *rpdev, void *buf, int len,
skb_queue_tail(&eptdev->queue, skb);
spin_unlock(&eptdev->queue_lock);

- /* wake up any blocking processes, waiting for new data */
+ wake_up_interruptible(&eptdev->readq);
+
+ return 0;
+}
+
+static int rpmsg_ept_flow_cb(struct rpmsg_device *rpdev, void *priv, bool enable)
+{
+ struct rpmsg_eptdev *eptdev = priv;
+
+ if (enable)
+ eptdev->remote_signals = TIOCM_DSR | TIOCM_CTS;
+ else
+ eptdev->remote_signals = 0;
+
+ eptdev->signals_pending = true;
+
wake_up_interruptible(&eptdev->readq);

return 0;
@@ -146,6 +164,7 @@ static int rpmsg_eptdev_open(struct inode *inode, struct file *filp)
return -EINVAL;
}

+ ept->flow_cb = rpmsg_ept_flow_cb;
eptdev->ept = ept;
filp->private_data = eptdev;
mutex_unlock(&eptdev->ept_lock);
@@ -166,6 +185,7 @@ static int rpmsg_eptdev_release(struct inode *inode, struct file *filp)
eptdev->ept = NULL;
}
mutex_unlock(&eptdev->ept_lock);
+ eptdev->signals_pending = false;

/* Discard all SKBs */
skb_queue_purge(&eptdev->queue);
@@ -279,6 +299,9 @@ static __poll_t rpmsg_eptdev_poll(struct file *filp, poll_table *wait)
if (!skb_queue_empty(&eptdev->queue))
mask |= EPOLLIN | EPOLLRDNORM;

+ if (eptdev->signals_pending)
+ mask |= EPOLLPRI;
+
mask |= rpmsg_poll(eptdev->ept, filp, wait);

return mask;
@@ -289,14 +312,35 @@ static long rpmsg_eptdev_ioctl(struct file *fp, unsigned int cmd,
{
struct rpmsg_eptdev *eptdev = fp->private_data;

- if (cmd != RPMSG_DESTROY_EPT_IOCTL)
- return -EINVAL;
-
- /* Don't allow to destroy a default endpoint. */
- if (eptdev->default_ept)
- return -EINVAL;
+ bool set;
+ u32 val;
+ int ret;
+
+ switch (cmd) {
+ case TIOCMGET:
+ eptdev->signals_pending = false;
+ ret = put_user(eptdev->remote_signals, (int __user *)arg);
+ break;
+ case TIOCMSET:
+ ret = get_user(val, (int __user *)arg);
+ if (ret)
+ break;
+ set = (val & (TIOCM_DTR | TIOCM_RTS)) ? true : false;
+ ret = rpmsg_set_flow_control(eptdev->ept, set);
+ break;
+ case RPMSG_DESTROY_EPT_IOCTL:
+ /* Don't allow to destroy a default endpoint. */
+ if (eptdev->default_ept) {
+ ret = -EINVAL;
+ break;
+ }
+ ret = rpmsg_chrdev_eptdev_destroy(&eptdev->dev, NULL);
+ break;
+ default:
+ ret = -EINVAL;
+ }

- return rpmsg_chrdev_eptdev_destroy(&eptdev->dev, NULL);
+ return ret;
}

static const struct file_operations rpmsg_eptdev_fops = {
--
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