isdn/gigaset: honor CAPI application's buffer size request

Fix the Gigaset CAPI driver to limit the length of a connection's
payload data receive buffers to the corresponding CAPI application's
data buffer size, as some real-life CAPI applications tend to be
rather unhappy if they receive bigger data blocks than requested.

Impact: bugfix
Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/isdn/gigaset/i4l.c b/drivers/isdn/gigaset/i4l.c
index c22e5ac..f01c3c2 100644
--- a/drivers/isdn/gigaset/i4l.c
+++ b/drivers/isdn/gigaset/i4l.c
@@ -16,7 +16,10 @@
 #include "gigaset.h"
 #include <linux/isdnif.h>
 
+#define SBUFSIZE	4096	/* sk_buff payload size */
+#define TRANSBUFSIZE	768	/* bytes per skb for transparent receive */
 #define HW_HDR_LEN	2	/* Header size used to store ack info */
+#define MAX_BUF_SIZE	(SBUFSIZE - HW_HDR_LEN)	/* max data packet from LL */
 
 /* == Handling of I4L IO =====================================================*/
 
@@ -231,6 +234,15 @@
 			dev_err(cs->dev, "ISDN_CMD_DIAL: channel not free\n");
 			return -EBUSY;
 		}
+		switch (bcs->proto2) {
+		case L2_HDLC:
+			bcs->rx_bufsize = SBUFSIZE;
+			break;
+		default:			/* assume transparent */
+			bcs->rx_bufsize = TRANSBUFSIZE;
+		}
+		dev_kfree_skb(bcs->rx_skb);
+		gigaset_new_rx_skb(bcs);
 
 		commands = kzalloc(AT_NUM*(sizeof *commands), GFP_ATOMIC);
 		if (!commands) {
@@ -314,6 +326,15 @@
 			return -EINVAL;
 		}
 		bcs = cs->bcs + ch;
+		switch (bcs->proto2) {
+		case L2_HDLC:
+			bcs->rx_bufsize = SBUFSIZE;
+			break;
+		default:			/* assume transparent */
+			bcs->rx_bufsize = TRANSBUFSIZE;
+		}
+		dev_kfree_skb(bcs->rx_skb);
+		gigaset_new_rx_skb(bcs);
 		if (!gigaset_add_event(cs, &bcs->at_state,
 				       EV_ACCEPT, NULL, 0, NULL))
 			return -ENOMEM;