Re: CDC-ACM driver: acm_set_control should be optional

According to the USB CDC class specification, line state control
is an optional feature for ACM devices. However, the cdc-acm driver
bails out when acm_set_control() fails while opening the device.

The proposed patch changes that behaviour: Failure of acm_set_control
is now only considered an error if the device is advertising the line
control feature in its capability mask.

Signed-off-by: Joris van Rantwijk <[email protected]>


diff -ur -U5 linux-2.6.19.2-orig/drivers/usb/class/cdc-acm.c linux-2.6.19.2/drivers/usb/class/cdc-acm.c
--- linux-2.6.19.2-orig/drivers/usb/class/cdc-acm.c	2007-01-10 20:10:37.000000000 +0100
+++ linux-2.6.19.2/drivers/usb/class/cdc-acm.c	2007-02-01 21:07:36.000000000 +0100
@@ -465,11 +465,12 @@
 	if (usb_submit_urb(acm->ctrlurb, GFP_KERNEL)) {
 		dbg("usb_submit_urb(ctrl irq) failed");
 		goto bail_out;
 	}
 
-	if (0 > acm_set_control(acm, acm->ctrlout = ACM_CTRL_DTR | ACM_CTRL_RTS))
+	if (0 > acm_set_control(acm, acm->ctrlout = ACM_CTRL_DTR | ACM_CTRL_RTS) &&
+	    (acm->ctrl_caps & ACM_CTRL_CAP_LINE))
 		goto full_bailout;
 
 	INIT_LIST_HEAD(&acm->spare_read_urbs);
 	INIT_LIST_HEAD(&acm->spare_read_bufs);
 	INIT_LIST_HEAD(&acm->filled_read_bufs);
diff -ur -U5 linux-2.6.19.2-orig/drivers/usb/class/cdc-acm.h linux-2.6.19.2/drivers/usb/class/cdc-acm.h
--- linux-2.6.19.2-orig/drivers/usb/class/cdc-acm.h	2007-01-10 20:10:37.000000000 +0100
+++ linux-2.6.19.2/drivers/usb/class/cdc-acm.h	2007-02-01 21:06:24.000000000 +0100
@@ -45,10 +45,13 @@
 
 #define ACM_CTRL_FRAMING	0x10
 #define ACM_CTRL_PARITY		0x20
 #define ACM_CTRL_OVERRUN	0x40
 
+#define ACM_CTRL_CAP_LINE	0x02
+#define ACM_CTRL_CAP_BRK	0x04
+
 /*
  * Internal driver structures.
  */
 
 /*

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