[PATCH] USB: cdc-acm: add a new special case for modems with buggy firmware

this fixes the "duplicated text" bug. There's a modem that cannot cope
with large transfers and more than one urb in flight. This patch adds a
special case to the driver.

Signed-off-by: Oliver Neukum <oliver@neukum.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 9 insertions, 7 deletions

diff --git a/drivers/usb/class/cdc-acm.h b/drivers/usb/class/cdc-acm.h
index fd2aaccdcbac..1bcaea32cfc1 100644
--- a/drivers/usb/class/cdc-acm.h
+++ b/drivers/usb/class/cdc-acm.h
@@ -56,11 +56,11 @@
  * in line disciplines. They ask for empty space amount, receive our URB size,
  * and proceed to issue several 1-character writes, assuming they will fit.
  * The very first write takes a complete URB. Fortunately, this only happens
- * when processing onlcr, so we only need 2 buffers.
+ * when processing onlcr, so we only need 2 buffers. These values must be
+ * powers of 2.
  */
-#define ACM_NWB  2
-#define ACM_NRU  16
-#define ACM_NRB  16
+#define ACM_NW  2
+#define ACM_NR  16
 
 struct acm_wb {
         unsigned char *buf;
@@ -91,9 +91,10 @@ struct acm {
         struct urb *ctrlurb, *writeurb;                 /* urbs */
         u8 *ctrl_buffer;                                /* buffers of urbs */
         dma_addr_t ctrl_dma;                            /* dma handles of buffers */
-        struct acm_wb wb[ACM_NWB];
-        struct acm_ru ru[ACM_NRU];
-        struct acm_rb rb[ACM_NRB];
+        struct acm_wb wb[ACM_NW];
+        struct acm_ru ru[ACM_NR];
+        struct acm_rb rb[ACM_NR];
+        int rx_buflimit;
         int rx_endpoint;
         spinlock_t read_lock;
         struct list_head spare_read_urbs;
@@ -122,3 +123,4 @@ struct acm {
 
 /* constants describing various quirks and errors */
 #define NO_UNION_NORMAL                 1
+#define SINGLE_RX_URB                   2