diff mbox series

[08/10] net: wwan: core: implement TIOCINQ ioctl

Message ID 20210608040241.10658-9-ryazanov.s.a@gmail.com (mailing list archive)
State Not Applicable
Delegated to: Johannes Berg
Headers show
Series net: WWAN subsystem improvements | expand

Commit Message

Sergey Ryazanov June 8, 2021, 4:02 a.m. UTC 
It is quite common for a userpace program to fetch the buffered amount
of data in the rx queue to avoid the read block. Implement the TIOCINQ
ioctl to make the migration to the WWAN port usage smooth.

Despite the fact that the read call will return no more data than the
size of a first skb in the queue, TIOCINQ returns the entire amount of
buffered data (sum of all queued skbs). This is done to prevent the
breaking of programs that optimize reading, avoiding it if the buffered
amount of data is too small.

Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
---
 drivers/net/wwan/wwan_core.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

Comments

Loic Poulain June 8, 2021, 8:51 a.m. UTC | #1 
On Tue, 8 Jun 2021 at 06:02, Sergey Ryazanov <ryazanov.s.a@gmail.com> wrote:
>
> It is quite common for a userpace program to fetch the buffered amount
> of data in the rx queue to avoid the read block. Implement the TIOCINQ
> ioctl to make the migration to the WWAN port usage smooth.
>
> Despite the fact that the read call will return no more data than the
> size of a first skb in the queue, TIOCINQ returns the entire amount of
> buffered data (sum of all queued skbs). This is done to prevent the
> breaking of programs that optimize reading, avoiding it if the buffered
> amount of data is too small.
>
> Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>

Reviewed-by: Loic Poulain <loic.poulain@linaro.org>
diff mbox series

Patch

diff --git a/drivers/net/wwan/wwan_core.c b/drivers/net/wwan/wwan_core.c
index 9346b2661eb3..d5a197da4a41 100644
--- a/drivers/net/wwan/wwan_core.c
+++ b/drivers/net/wwan/wwan_core.c
@@ -12,6 +12,7 @@ 
 #include <linux/skbuff.h>
 #include <linux/slab.h>
 #include <linux/types.h>
+#include <linux/termios.h>
 #include <linux/wwan.h>
 
 /* Maximum number of minors in use */
@@ -618,6 +619,30 @@  static __poll_t wwan_port_fops_poll(struct file *filp, poll_table *wait)
 	return mask;
 }
 
+static long wwan_port_fops_ioctl(struct file *filp, unsigned int cmd,
+				 unsigned long arg)
+{
+	struct wwan_port *port = filp->private_data;
+
+	switch (cmd) {
+	case TIOCINQ: {	/* aka SIOCINQ aka FIONREAD */
+		unsigned long flags;
+		struct sk_buff *skb;
+		int amount = 0;
+
+		spin_lock_irqsave(&port->rxq.lock, flags);
+		skb_queue_walk(&port->rxq, skb)
+			amount += skb->len;
+		spin_unlock_irqrestore(&port->rxq.lock, flags);
+
+		return put_user(amount, (int __user *)arg);
+	}
+
+	default:
+		return -ENOIOCTLCMD;
+	}
+}
+
 static const struct file_operations wwan_port_fops = {
 	.owner = THIS_MODULE,
 	.open = wwan_port_fops_open,
@@ -625,6 +650,10 @@  static const struct file_operations wwan_port_fops = {
 	.read = wwan_port_fops_read,
 	.write = wwan_port_fops_write,
 	.poll = wwan_port_fops_poll,
+	.unlocked_ioctl = wwan_port_fops_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl = compat_ptr_ioctl,
+#endif
 	.llseek = noop_llseek,
 };