This patch adds a dummy implementation of the TCGETS and TCSETS ioctls
to cdc-wdm. This is necessary for userspace applications like "chat".
cdc-wdm devices are similar to cdc-acm devices, except for the lack of a
bulk data interface. This makes them useful in dialling applications
and chatscripts. However, some of these userspace applications assume
they are talking to a TTY device and fail with cdc-wdm devices:
nemi:/tmp# chat -t 5 -v -s "" "AT" "OK" > /dev/cdc-wdm0 < /dev/cdc-wdm0
Can't get terminal parameters: Inappropriate ioctl for device
This is a workaround for the problem.
Signed-off-by: Bjørn Mork <bjorn@xxxxxxx>
---
Note: I have not understood why cdc-wdm isn't a fullblown TTY driver,
like cdc-acm is. Could anyone care to explain?
The correct fix for the described problem may be changing cdc-wdm to use
the TTY layer, but I guess that means renaming the devices and possibly
other very userspace visible changes? Let me know if this is desired,
and I'll try to provide a patch.
diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index 3771d6e..ce5bac2 100644
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -14,6 +14,7 @@
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/slab.h>
+#include <linux/tty.h>
#include <linux/module.h>
#include <linux/smp_lock.h>
#include <linux/mutex.h>
@@ -555,10 +556,27 @@ static int wdm_release(struct inode *inode, struct file *file)
return 0;
}
+static long wdm_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+ struct wdm_device *desc = file->private_data;
+
+ if (!desc)
+ return -ENODEV;
+
+ switch (cmd) {
+ case TCGETS:
+ case TCSETS:
+ return 0;
+ default:
+ return -ENOTTY;
+ }
+}
+
static const struct file_operations wdm_fops = {
.owner = THIS_MODULE,
.read = wdm_read,
.write = wdm_write,
+ .unlocked_ioctl = wdm_ioctl,
.open = wdm_open,
.flush = wdm_flush,
.release = wdm_release,
--
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