Added possibility to force the slcan driver to use a specific device number

when set via SWTC char (e.g. with stty). See thread
https://lists.berlios.de/pipermail/socketcan-users/2010-April/001378.html
Provided by Stephen Hellriegel <Stephen.Hellriegel@verari.com>
So far this change only applies for Kernels < 2.6.32 ...

git-svn-id: svn://svn.berlios.de//socketcan/trunk@1170 030b6a49-0b11-0410-94ab-b0dab22257f2

diff --git a/kernel/2.6/drivers/net/can/slcan.c b/kernel/2.6/drivers/net/can/slcan.c
index dd29d7d6cd7cba9775bf5174a08335fc2bc524ef..3cbb9b80b1a16191c139f8755065bf36cd4c0fbc 100644 (file)
--- a/kernel/2.6/drivers/net/can/slcan.c
+++ b/kernel/2.6/drivers/net/can/slcan.c
@@ -623,7 +623,7 @@ static void slc_sync(void)
 
 
 /* Find a free SLCAN channel, and link in this `tty' line. */
-static struct slcan *slc_alloc(dev_t line)
+static struct slcan *slc_alloc(dev_t line, char forcednum)
 {
        int i;
 #if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,32)
@@ -680,10 +680,18 @@ static struct slcan *slc_alloc(dev_t line)
                }
        }
 
+       /* Check if the user specified an exact interface to use */
+       if (forcednum) {
+               sel = forcednum - '0';
+               score = 0;
+               i = sel;
+               dev = slcan_devs[i];
+       }
+
        if (sel >= 0) {
                i = sel;
                dev = slcan_devs[i];
-               if (score > 1) {
+               if ((score > 1) && (dev)) {
                        sl = netdev_priv(dev);
                        sl->flags &= (1 << SLF_INUSE);
                        return sl;
@@ -766,7 +774,21 @@ static int slcan_open(struct tty_struct *tty)
 
        /* OK.  Find a free SLCAN channel to use. */
        err = -ENFILE;
-       sl = slc_alloc(tty_devnum(tty));
+
+       /* Look to see if the user has requested a specific channel
+        * to be used (encoded as '0' plus the interface number requested in
+        * the otherwise unused swtch termios variable )
+        * stty swtch 'channel' device
+        *  where 'channel' is '0' to maxdevs (0)
+        *  where device is the name of the serial device (/dev/ttyUSB0)
+        */
+       if ((SWTC_CHAR(tty)>='0') && (SWTC_CHAR(tty)<'0'+maxdev)){
+               sl = slc_alloc(tty_devnum(tty),SWTC_CHAR(tty));
+       } else {
+               /* OK.  Find a free SLCAN channel to use. */
+               sl = slc_alloc(tty_devnum(tty),0);
+       }
+
        if (sl == NULL)
                goto err_exit;