USB: allow users to run setserial with cdc-acm

We had a user report that running setserial on /dev/ttyACM0 didn't work.
He pointed at an old patch by Oliver Neukum from 2008 that never went anywhere..
http://permalink.gmane.org/gmane.linux.usb.general/9236

I made some minor changes to get it to apply again, and got the user to retest on 3.1,
and he reported it worked for him. https://bugzilla.redhat.com/show_bug.cgi?id=787607

The diff below is against 3.3rc. The only difference between this and
the version the user tested is the removal of the if (!ACM_READY) test
Havard removed ACM_READY in 99823f457d5994b3bd3775515578c8bfacc64b04
I'm unclear if there's need for a different test in its place.

From: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Dave Jones <davej@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 29 insertions, 1 deletions

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 9543b19d410c..6dcc3a3fe6d1 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -39,6 +39,7 @@
 #include <linux/serial.h>
 #include <linux/tty_driver.h>
 #include <linux/tty_flip.h>
+#include <linux/serial.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/uaccess.h>
@@ -773,10 +774,37 @@ static int acm_tty_tiocmset(struct tty_struct *tty,
         return acm_set_control(acm, acm->ctrlout = newctrl);
 }
 
+static int get_serial_info(struct acm *acm, struct serial_struct __user *info)
+{
+        struct serial_struct tmp;
+
+        if (!info)
+                return -EINVAL;
+
+        memset(&tmp, 0, sizeof(tmp));
+        tmp.flags = ASYNC_LOW_LATENCY;
+        tmp.xmit_fifo_size = acm->writesize;
+        tmp.baud_base = le32_to_cpu(acm->line.dwDTERate);
+
+        if (copy_to_user(info, &tmp, sizeof(tmp)))
+                return -EFAULT;
+        else
+                return 0;
+}
+
 static int acm_tty_ioctl(struct tty_struct *tty,
                                         unsigned int cmd, unsigned long arg)
 {
-        return -ENOIOCTLCMD;
+        struct acm *acm = tty->driver_data;
+        int rv = -ENOIOCTLCMD;
+
+        switch (cmd) {
+        case TIOCGSERIAL: /* gets serial port data */
+                rv = get_serial_info(acm, (struct serial_struct __user *) arg);
+                break;
+        }
+
+        return rv;
 }
 
 static const __u32 acm_tty_speed[] = {