[PATCH] USB: fix acm trouble with terminals

This patch fixes lost LF when ACM device is used with getty/login/bash,
in case of a modem which takes calls.

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

1 files changed, 22 insertions, 3 deletions

diff --git a/drivers/usb/class/cdc-acm.h b/drivers/usb/class/cdc-acm.h
index 9009114e311b..963a5dfd2096 100644
--- a/drivers/usb/class/cdc-acm.h
+++ b/drivers/usb/class/cdc-acm.h
@@ -51,14 +51,34 @@
  * Internal driver structures.
  */
 
+/*
+ * The only reason to have several buffers is to accomodate assumptions
+ * 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.
+ */
+#define ACM_NWB  2
+struct acm_wb {
+        unsigned char *buf;
+        dma_addr_t dmah;
+        int len;
+        int use;
+};
+
 struct acm {
         struct usb_device *dev;                         /* the corresponding usb device */
         struct usb_interface *control;                  /* control interface */
         struct usb_interface *data;                     /* data interface */
         struct tty_struct *tty;                         /* the corresponding tty */
         struct urb *ctrlurb, *readurb, *writeurb;       /* urbs */
-        u8 *ctrl_buffer, *read_buffer, *write_buffer;   /* buffers of urbs */
-        dma_addr_t ctrl_dma, read_dma, write_dma;       /* dma handles of buffers */
+        u8 *ctrl_buffer, *read_buffer;                  /* buffers of urbs */
+        dma_addr_t ctrl_dma, read_dma;                  /* dma handles of buffers */
+        struct acm_wb wb[ACM_NWB];
+        int write_current;                              /* current write buffer */
+        int write_used;                                 /* number of non-empty write buffers */
+        int write_ready;                                /* write urb is not running */
+        spinlock_t write_lock;
         struct usb_cdc_line_coding line;                /* bits, stop, parity */
         struct work_struct work;                        /* work queue entry for line discipline waking up */
         struct tasklet_struct bh;                       /* rx processing */
@@ -71,7 +91,6 @@ struct acm {
         unsigned int minor;                             /* acm minor number */
         unsigned char throttle;                         /* throttled by tty layer */
         unsigned char clocal;                           /* termios CLOCAL */
-        unsigned char ready_for_write;                  /* write urb can be used */
         unsigned char resubmit_to_unthrottle;           /* throtteling has disabled the read urb */
         unsigned int ctrl_caps;                         /* control capabilities from the class specific header */
 };