mISDN: Allow to set a minimum length for transparent data

If the FIFO of the card is small, many short messages are queued up to
the upper layers and the userspace. This change allows the applications
to set a minimum datalen they want from the drivers.
Create a common control function to avoid code duplication in each
driver.

Signed-off-by: Karsten Keil <kkeil@linux-pingi.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

10 files changed, 117 insertions, 128 deletions

diff --git a/drivers/isdn/hardware/mISDN/avmfritz.c b/drivers/isdn/hardware/mISDN/avmfritz.c
index 8081367..7cd3a96 100644
--- a/drivers/isdn/hardware/mISDN/avmfritz.c
+++ b/drivers/isdn/hardware/mISDN/avmfritz.c
@@ -536,12 +536,12 @@ HDLC_irq(struct bchannel *bch, u32 stat)
 			hdlc_empty_fifo(bch, len);
 			if (!bch->rx_skb)
 				goto handle_tx;
-			if (test_bit(FLG_TRANSPARENT, &bch->Flags) ||
-			    (stat & HDLC_STAT_RME)) {
-				if (((stat & HDLC_STAT_CRCVFRRAB) ==
-				     HDLC_STAT_CRCVFR) ||
-				    test_bit(FLG_TRANSPARENT, &bch->Flags)) {
-					recv_Bchannel(bch, 0);
+			if (test_bit(FLG_TRANSPARENT, &bch->Flags)) {
+				recv_Bchannel(bch, 0, false);
+			} else if (stat & HDLC_STAT_RME) {
+				if ((stat & HDLC_STAT_CRCVFRRAB) ==
+				    HDLC_STAT_CRCVFR) {
+					recv_Bchannel(bch, 0, false);
 				} else {
 					pr_warning("%s: got invalid frame\n",
 						   fc->name);
@@ -809,21 +809,7 @@ init_card(struct fritzcard *fc)
 static int
 channel_bctrl(struct bchannel *bch, struct mISDN_ctrl_req *cq)
 {
-	int ret = 0;
-	struct fritzcard *fc = bch->hw;
-
-	switch (cq->op) {
-	case MISDN_CTRL_GETOP:
-		cq->op = 0;
-		break;
-		/* Nothing implemented yet */
-	case MISDN_CTRL_FILL_EMPTY:
-	default:
-		pr_info("%s: %s unknown Op %x\n", fc->name, __func__, cq->op);
-		ret = -EINVAL;
-		break;
-	}
-	return ret;
+	return mISDN_ctrl_bchannel(bch, cq);
 }
 
 static int
@@ -1019,6 +1005,7 @@ static int __devinit
 setup_instance(struct fritzcard *card)
 {
 	int i, err;
+	unsigned short minsize;
 	u_long flags;
 
 	snprintf(card->name, MISDN_MAX_IDLEN - 1, "AVM.%d", AVM_cnt + 1);
@@ -1038,7 +1025,11 @@ setup_instance(struct fritzcard *card)
 	for (i = 0; i < 2; i++) {
 		card->bch[i].nr = i + 1;
 		set_channelmap(i + 1, card->isac.dch.dev.channelmap);
-		mISDN_initbchannel(&card->bch[i], MAX_DATA_MEM);
+		if (AVM_FRITZ_PCIV2 == card->type)
+			minsize = HDLC_FIFO_SIZE_V2;
+		else
+			minsize = HDLC_FIFO_SIZE_V1;
+		mISDN_initbchannel(&card->bch[i], MAX_DATA_MEM, minsize);
 		card->bch[i].hw = card;
 		card->bch[i].ch.send = avm_l2l1B;
 		card->bch[i].ch.ctrl = avm_bctrl;
diff --git a/drivers/isdn/hardware/mISDN/hfcmulti.c b/drivers/isdn/hardware/mISDN/hfcmulti.c
index 60dd6ef..3d4b36d 100644
--- a/drivers/isdn/hardware/mISDN/hfcmulti.c
+++ b/drivers/isdn/hardware/mISDN/hfcmulti.c
@@ -2352,7 +2352,7 @@ next_frame:
 			if (dch)
 				recv_Dchannel(dch);
 			else
-				recv_Bchannel(bch, MISDN_ID_ANY);
+				recv_Bchannel(bch, MISDN_ID_ANY, false);
 			*sp = skb;
 			again++;
 			goto next_frame;
@@ -2367,7 +2367,7 @@ next_frame:
 			       "(z1=%04x, z2=%04x) TRANS\n",
 			       __func__, hc->id + 1, ch, Zsize, z1, z2);
 		/* only bch is transparent */
-		recv_Bchannel(bch, hc->chan[ch].Zfill);
+		recv_Bchannel(bch, hc->chan[ch].Zfill, false);
 	}
 }
 
@@ -3574,8 +3574,9 @@ channel_bctrl(struct bchannel *bch, struct mISDN_ctrl_req *cq)
 
 	switch (cq->op) {
 	case MISDN_CTRL_GETOP:
-		cq->op = MISDN_CTRL_HFC_OP | MISDN_CTRL_HW_FEATURES_OP
-			| MISDN_CTRL_RX_OFF | MISDN_CTRL_FILL_EMPTY;
+		ret = mISDN_ctrl_bchannel(bch, cq);
+		cq->op |= MISDN_CTRL_HFC_OP | MISDN_CTRL_HW_FEATURES_OP |
+			  MISDN_CTRL_RX_OFF | MISDN_CTRL_FILL_EMPTY;
 		break;
 	case MISDN_CTRL_RX_OFF: /* turn off / on rx stream */
 		hc->chan[bch->slot].rx_off = !!cq->p1;
@@ -3683,9 +3684,7 @@ channel_bctrl(struct bchannel *bch, struct mISDN_ctrl_req *cq)
 			ret = -EINVAL;
 		break;
 	default:
-		printk(KERN_WARNING "%s: unknown Op %x\n",
-		       __func__, cq->op);
-		ret = -EINVAL;
+		ret = mISDN_ctrl_bchannel(bch, cq);
 		break;
 	}
 	return ret;
@@ -4855,7 +4854,7 @@ init_e1_port(struct hfc_multi *hc, struct hm_map *m, int pt)
 		bch->nr = ch;
 		bch->slot = ch;
 		bch->debug = debug;
-		mISDN_initbchannel(bch, MAX_DATA_MEM);
+		mISDN_initbchannel(bch, MAX_DATA_MEM, poll >> 1);
 		bch->hw = hc;
 		bch->ch.send = handle_bmsg;
 		bch->ch.ctrl = hfcm_bctrl;
@@ -4928,7 +4927,7 @@ init_multi_port(struct hfc_multi *hc, int pt)
 		bch->nr = ch + 1;
 		bch->slot = i + ch;
 		bch->debug = debug;
-		mISDN_initbchannel(bch, MAX_DATA_MEM);
+		mISDN_initbchannel(bch, MAX_DATA_MEM, poll >> 1);
 		bch->hw = hc;
 		bch->ch.send = handle_bmsg;
 		bch->ch.ctrl = hfcm_bctrl;
diff --git a/drivers/isdn/hardware/mISDN/hfcpci.c b/drivers/isdn/hardware/mISDN/hfcpci.c
index 0622e05..2774375 100644
--- a/drivers/isdn/hardware/mISDN/hfcpci.c
+++ b/drivers/isdn/hardware/mISDN/hfcpci.c
@@ -453,7 +453,7 @@ hfcpci_empty_bfifo(struct bchannel *bch, struct bzfifo *bz,
 		}
 		bz->za[new_f2].z2 = cpu_to_le16(new_z2);
 		bz->f2 = new_f2;	/* next buffer */
-		recv_Bchannel(bch, MISDN_ID_ANY);
+		recv_Bchannel(bch, MISDN_ID_ANY, false);
 	}
 }
 
@@ -599,7 +599,7 @@ hfcpci_empty_fifo_trans(struct bchannel *bch, struct bzfifo *rxbz,
 			ptr1 = bdata;	/* start of buffer */
 			memcpy(ptr, ptr1, fcnt_rx);	/* rest */
 		}
-		recv_Bchannel(bch, fcnt_tx); /* bch, id */
+		recv_Bchannel(bch, fcnt_tx, false); /* bch, id, !force */
 	}
 	*z2r = cpu_to_le16(new_z2);		/* new position */
 }
@@ -1535,7 +1535,8 @@ channel_bctrl(struct bchannel *bch, struct mISDN_ctrl_req *cq)
 
 	switch (cq->op) {
 	case MISDN_CTRL_GETOP:
-		cq->op = MISDN_CTRL_FILL_EMPTY;
+		ret = mISDN_ctrl_bchannel(bch, cq);
+		cq->op |= MISDN_CTRL_FILL_EMPTY;
 		break;
 	case MISDN_CTRL_FILL_EMPTY: /* fill fifo, if empty */
 		test_and_set_bit(FLG_FILLEMPTY, &bch->Flags);
@@ -1544,8 +1545,7 @@ channel_bctrl(struct bchannel *bch, struct mISDN_ctrl_req *cq)
 			       "off=%d)\n", __func__, bch->nr, !!cq->p1);
 		break;
 	default:
-		printk(KERN_WARNING "%s: unknown Op %x\n", __func__, cq->op);
-		ret = -EINVAL;
+		ret = mISDN_ctrl_bchannel(bch, cq);
 		break;
 	}
 	return ret;
@@ -2116,7 +2116,7 @@ setup_card(struct hfc_pci *card)
 		card->bch[i].nr = i + 1;
 		set_channelmap(i + 1, card->dch.dev.channelmap);
 		card->bch[i].debug = debug;
-		mISDN_initbchannel(&card->bch[i], MAX_DATA_MEM);
+		mISDN_initbchannel(&card->bch[i], MAX_DATA_MEM, poll >> 1);
 		card->bch[i].hw = card;
 		card->bch[i].ch.send = hfcpci_l2l1B;
 		card->bch[i].ch.ctrl = hfc_bctrl;
diff --git a/drivers/isdn/hardware/mISDN/hfcsusb.c b/drivers/isdn/hardware/mISDN/hfcsusb.c
index 6bb689b..9c17473 100644
--- a/drivers/isdn/hardware/mISDN/hfcsusb.c
+++ b/drivers/isdn/hardware/mISDN/hfcsusb.c
@@ -810,7 +810,8 @@ channel_bctrl(struct bchannel *bch, struct mISDN_ctrl_req *cq)
 
 	switch (cq->op) {
 	case MISDN_CTRL_GETOP:
-		cq->op = MISDN_CTRL_FILL_EMPTY;
+		ret = mISDN_ctrl_bchannel(bch, cq);
+		cq->op |= MISDN_CTRL_FILL_EMPTY;
 		break;
 	case MISDN_CTRL_FILL_EMPTY: /* fill fifo, if empty */
 		test_and_set_bit(FLG_FILLEMPTY, &bch->Flags);
@@ -819,8 +820,7 @@ channel_bctrl(struct bchannel *bch, struct mISDN_ctrl_req *cq)
 			       "off=%d)\n", __func__, bch->nr, !!cq->p1);
 		break;
 	default:
-		printk(KERN_WARNING "%s: unknown Op %x\n", __func__, cq->op);
-		ret = -EINVAL;
+		ret = mISDN_ctrl_bchannel(bch, cq);
 		break;
 	}
 	return ret;
@@ -931,7 +931,8 @@ hfcsusb_rx_frame(struct usb_fifo *fifo, __u8 *data, unsigned int len,
 				if (fifo->dch)
 					recv_Dchannel(fifo->dch);
 				if (fifo->bch)
-					recv_Bchannel(fifo->bch, MISDN_ID_ANY);
+					recv_Bchannel(fifo->bch, MISDN_ID_ANY,
+						      0);
 				if (fifo->ech)
 					recv_Echannel(fifo->ech,
 						      &hw->dch);
@@ -952,8 +953,7 @@ hfcsusb_rx_frame(struct usb_fifo *fifo, __u8 *data, unsigned int len,
 		}
 	} else {
 		/* deliver transparent data to layer2 */
-		if (rx_skb->len >= poll)
-			recv_Bchannel(fifo->bch, MISDN_ID_ANY);
+		recv_Bchannel(fifo->bch, MISDN_ID_ANY, false);
 	}
 	spin_unlock(&hw->lock);
 }
@@ -1861,7 +1861,7 @@ setup_instance(struct hfcsusb *hw, struct device *parent)
 		hw->bch[i].nr = i + 1;
 		set_channelmap(i + 1, hw->dch.dev.channelmap);
 		hw->bch[i].debug = debug;
-		mISDN_initbchannel(&hw->bch[i], MAX_DATA_MEM);
+		mISDN_initbchannel(&hw->bch[i], MAX_DATA_MEM, poll >> 1);
 		hw->bch[i].hw = hw;
 		hw->bch[i].ch.send = hfcusb_l2l1B;
 		hw->bch[i].ch.ctrl = hfc_bctrl;
diff --git a/drivers/isdn/hardware/mISDN/mISDNipac.c b/drivers/isdn/hardware/mISDN/mISDNipac.c
index 7d109ed..3e71a5e 100644
--- a/drivers/isdn/hardware/mISDN/mISDNipac.c
+++ b/drivers/isdn/hardware/mISDN/mISDNipac.c
@@ -1063,7 +1063,7 @@ ipac_rme(struct hscx_hw *hx)
 		skb_trim(hx->bch.rx_skb, 0);
 	} else {
 		skb_trim(hx->bch.rx_skb, hx->bch.rx_skb->len - 1);
-		recv_Bchannel(&hx->bch, 0);
+		recv_Bchannel(&hx->bch, 0, false);
 	}
 }
 
@@ -1114,11 +1114,8 @@ ipac_irq(struct hscx_hw *hx, u8 ista)
 
 	if (istab & IPACX_B_RPF) {
 		hscx_empty_fifo(hx, hx->fifo_size);
-		if (test_bit(FLG_TRANSPARENT, &hx->bch.Flags)) {
-			/* receive transparent audio data */
-			if (hx->bch.rx_skb)
-				recv_Bchannel(&hx->bch, 0);
-		}
+		if (test_bit(FLG_TRANSPARENT, &hx->bch.Flags))
+			recv_Bchannel(&hx->bch, 0, false);
 	}
 
 	if (istab & IPACX_B_RFO) {
@@ -1377,20 +1374,7 @@ hscx_l2l1(struct mISDNchannel *ch, struct sk_buff *skb)
 static int
 channel_bctrl(struct bchannel *bch, struct mISDN_ctrl_req *cq)
 {
-	int	ret = 0;
-
-	switch (cq->op) {
-	case MISDN_CTRL_GETOP:
-		cq->op = 0;
-		break;
-		/* Nothing implemented yet */
-	case MISDN_CTRL_FILL_EMPTY:
-	default:
-		pr_info("%s: unknown Op %x\n", __func__, cq->op);
-		ret = -EINVAL;
-		break;
-	}
-	return ret;
+	return mISDN_ctrl_bchannel(bch, cq);
 }
 
 static int
@@ -1608,7 +1592,8 @@ mISDNipac_init(struct ipac_hw *ipac, void *hw)
 		set_channelmap(i + 1, ipac->isac.dch.dev.channelmap);
 		list_add(&ipac->hscx[i].bch.ch.list,
 			 &ipac->isac.dch.dev.bchannels);
-		mISDN_initbchannel(&ipac->hscx[i].bch, MAX_DATA_MEM);
+		mISDN_initbchannel(&ipac->hscx[i].bch, MAX_DATA_MEM,
+				   ipac->hscx[i].fifo_size);
 		ipac->hscx[i].bch.ch.nr = i + 1;
 		ipac->hscx[i].bch.ch.send = &hscx_l2l1;
 		ipac->hscx[i].bch.ch.ctrl = hscx_bctrl;
diff --git a/drivers/isdn/hardware/mISDN/mISDNisar.c b/drivers/isdn/hardware/mISDN/mISDNisar.c
index 4169bb2d..e74ad38 100644
--- a/drivers/isdn/hardware/mISDN/mISDNisar.c
+++ b/drivers/isdn/hardware/mISDN/mISDNisar.c
@@ -446,7 +446,7 @@ isar_rcv_frame(struct isar_ch *ch)
 			break;
 		}
 		rcv_mbox(ch->is, skb_put(ch->bch.rx_skb, ch->is->clsb));
-		recv_Bchannel(&ch->bch, 0);
+		recv_Bchannel(&ch->bch, 0, false);
 		break;
 	case ISDN_P_B_HDLC:
 		maxlen = bchannel_get_rxbuf(&ch->bch, ch->is->clsb);
@@ -481,7 +481,7 @@ isar_rcv_frame(struct isar_ch *ch)
 				break;
 			}
 			skb_trim(ch->bch.rx_skb, ch->bch.rx_skb->len - 2);
-			recv_Bchannel(&ch->bch, 0);
+			recv_Bchannel(&ch->bch, 0, false);
 		}
 		break;
 	case ISDN_P_B_T30_FAX:
@@ -517,7 +517,7 @@ isar_rcv_frame(struct isar_ch *ch)
 				ch->state = STFAX_ESCAPE;
 				/* set_skb_flag(skb, DF_NOMOREDATA); */
 			}
-			recv_Bchannel(&ch->bch, 0);
+			recv_Bchannel(&ch->bch, 0, false);
 			if (ch->is->cmsb & SART_NMD)
 				deliver_status(ch, HW_MOD_NOCARR);
 			break;
@@ -557,7 +557,7 @@ isar_rcv_frame(struct isar_ch *ch)
 				break;
 			}
 			skb_trim(ch->bch.rx_skb, ch->bch.rx_skb->len - 2);
-			recv_Bchannel(&ch->bch, 0);
+			recv_Bchannel(&ch->bch, 0, false);
 		}
 		if (ch->is->cmsb & SART_NMD) { /* ABORT */
 			pr_debug("%s: isar_rcv_frame: no more data\n",
@@ -1554,20 +1554,7 @@ isar_l2l1(struct mISDNchannel *ch, struct sk_buff *skb)
 static int
 channel_bctrl(struct bchannel *bch, struct mISDN_ctrl_req *cq)
 {
-	int	ret = 0;
-
-	switch (cq->op) {
-	case MISDN_CTRL_GETOP:
-		cq->op = 0;
-		break;
-		/* Nothing implemented yet */
-	case MISDN_CTRL_FILL_EMPTY:
-	default:
-		pr_info("%s: unknown Op %x\n", __func__, cq->op);
-		ret = -EINVAL;
-		break;
-	}
-	return ret;
+	return mISDN_ctrl_bchannel(bch, cq);
 }
 
 static int
@@ -1665,7 +1652,7 @@ mISDNisar_init(struct isar_hw *isar, void *hw)
 	isar->hw = hw;
 	for (i = 0; i < 2; i++) {
 		isar->ch[i].bch.nr = i + 1;
-		mISDN_initbchannel(&isar->ch[i].bch, MAX_DATA_MEM);
+		mISDN_initbchannel(&isar->ch[i].bch, MAX_DATA_MEM, 32);
 		isar->ch[i].bch.ch.nr = i + 1;
 		isar->ch[i].bch.ch.send = &isar_l2l1;
 		isar->ch[i].bch.ch.ctrl = isar_bctrl;
diff --git a/drivers/isdn/hardware/mISDN/netjet.c b/drivers/isdn/hardware/mISDN/netjet.c
index 3f28057..47d3074 100644
--- a/drivers/isdn/hardware/mISDN/netjet.c
+++ b/drivers/isdn/hardware/mISDN/netjet.c
@@ -408,7 +408,7 @@ read_dma(struct tiger_ch *bc, u32 idx, int cnt)
 	}
 
 	if (test_bit(FLG_TRANSPARENT, &bc->bch.Flags)) {
-		recv_Bchannel(&bc->bch, 0);
+		recv_Bchannel(&bc->bch, 0, false);
 		return;
 	}
 
@@ -426,7 +426,7 @@ read_dma(struct tiger_ch *bc, u32 idx, int cnt)
 						     DUMP_PREFIX_OFFSET, p,
 						     stat);
 			}
-			recv_Bchannel(&bc->bch, 0);
+			recv_Bchannel(&bc->bch, 0, false);
 			stat = bchannel_get_rxbuf(&bc->bch, bc->bch.maxlen);
 			if (stat < 0) {
 				pr_warning("%s.B%d: No memory for %d bytes\n",
@@ -758,21 +758,7 @@ nj_l2l1B(struct mISDNchannel *ch, struct sk_buff *skb)
 static int
 channel_bctrl(struct tiger_ch *bc, struct mISDN_ctrl_req *cq)
 {
-	int ret = 0;
-	struct tiger_hw *card  = bc->bch.hw;
-
-	switch (cq->op) {
-	case MISDN_CTRL_GETOP:
-		cq->op = 0;
-		break;
-		/* Nothing implemented yet */
-	case MISDN_CTRL_FILL_EMPTY:
-	default:
-		pr_info("%s: %s unknown Op %x\n", card->name, __func__, cq->op);
-		ret = -EINVAL;
-		break;
-	}
-	return ret;
+	return mISDN_ctrl_bchannel(&bc->bch, cq);
 }
 
 static int
@@ -1006,7 +992,8 @@ setup_instance(struct tiger_hw *card)
 	for (i = 0; i < 2; i++) {
 		card->bc[i].bch.nr = i + 1;
 		set_channelmap(i + 1, card->isac.dch.dev.channelmap);
-		mISDN_initbchannel(&card->bc[i].bch, MAX_DATA_MEM);
+		mISDN_initbchannel(&card->bc[i].bch, MAX_DATA_MEM,
+				   NJ_DMA_RXSIZE >> 1);
 		card->bc[i].bch.hw = card;
 		card->bc[i].bch.ch.send = nj_l2l1B;
 		card->bc[i].bch.ch.ctrl = nj_bctrl;
diff --git a/drivers/isdn/hardware/mISDN/w6692.c b/drivers/isdn/hardware/mISDN/w6692.c
index 8324b20..03fb4a3 100644
--- a/drivers/isdn/hardware/mISDN/w6692.c
+++ b/drivers/isdn/hardware/mISDN/w6692.c
@@ -688,7 +688,7 @@ W6692B_interrupt(struct w6692_hw *card, int ch)
 			if (count == 0)
 				count = W_B_FIFO_THRESH;
 			W6692_empty_Bfifo(wch, count);
-			recv_Bchannel(&wch->bch, 0);
+			recv_Bchannel(&wch->bch, 0, false);
 		}
 	}
 	if (stat & W_B_EXI_RMR) {
@@ -704,9 +704,8 @@ W6692B_interrupt(struct w6692_hw *card, int ch)
 				    W_B_CMDR_RRST | W_B_CMDR_RACT);
 		} else {
 			W6692_empty_Bfifo(wch, W_B_FIFO_THRESH);
-			if (test_bit(FLG_TRANSPARENT, &wch->bch.Flags) &&
-			    wch->bch.rx_skb && (wch->bch.rx_skb->len > 0))
-				recv_Bchannel(&wch->bch, 0);
+			if (test_bit(FLG_TRANSPARENT, &wch->bch.Flags))
+				recv_Bchannel(&wch->bch, 0, false);
 		}
 	}
 	if (stat & W_B_EXI_RDOV) {
@@ -979,20 +978,7 @@ w6692_l2l1B(struct mISDNchannel *ch, struct sk_buff *skb)
 static int
 channel_bctrl(struct bchannel *bch, struct mISDN_ctrl_req *cq)
 {
-	int	ret = 0;
-
-	switch (cq->op) {
-	case MISDN_CTRL_GETOP:
-		cq->op = 0;
-		break;
-		/* Nothing implemented yet */
-	case MISDN_CTRL_FILL_EMPTY:
-	default:
-		pr_info("%s: unknown Op %x\n", __func__, cq->op);
-		ret = -EINVAL;
-		break;
-	}
-	return ret;
+	return mISDN_ctrl_bchannel(bch, cq);
 }
 
 static int
@@ -1303,7 +1289,8 @@ setup_instance(struct w6692_hw *card)
 	card->dch.hw = card;
 	card->dch.dev.nrbchan = 2;
 	for (i = 0; i < 2; i++) {
-		mISDN_initbchannel(&card->bc[i].bch, MAX_DATA_MEM);
+		mISDN_initbchannel(&card->bc[i].bch, MAX_DATA_MEM,
+				   W_B_FIFO_THRESH);
 		card->bc[i].bch.hw = card;
 		card->bc[i].bch.nr = i + 1;
 		card->bc[i].bch.ch.nr = i + 1;
diff --git a/drivers/isdn/mISDN/hwchannel.c b/drivers/isdn/mISDN/hwchannel.c
index 3c2145d..d42ad0e 100644
--- a/drivers/isdn/mISDN/hwchannel.c
+++ b/drivers/isdn/mISDN/hwchannel.c
@@ -81,10 +81,16 @@ mISDN_initdchannel(struct dchannel *ch, int maxlen, void *phf)
 EXPORT_SYMBOL(mISDN_initdchannel);
 
 int
-mISDN_initbchannel(struct bchannel *ch, int maxlen)
+mISDN_initbchannel(struct bchannel *ch, unsigned short maxlen,
+		   unsigned short minlen)
 {
 	ch->Flags = 0;
+	ch->minlen = minlen;
+	ch->next_minlen = minlen;
+	ch->init_minlen = minlen;
 	ch->maxlen = maxlen;
+	ch->next_maxlen = maxlen;
+	ch->init_maxlen = maxlen;
 	ch->hw = NULL;
 	ch->rx_skb = NULL;
 	ch->tx_skb = NULL;
@@ -134,6 +140,10 @@ mISDN_clear_bchannel(struct bchannel *ch)
 	test_and_clear_bit(FLG_TX_BUSY, &ch->Flags);
 	test_and_clear_bit(FLG_TX_NEXT, &ch->Flags);
 	test_and_clear_bit(FLG_ACTIVE, &ch->Flags);
+	ch->minlen = ch->init_minlen;
+	ch->next_minlen = ch->init_minlen;
+	ch->maxlen = ch->init_maxlen;
+	ch->next_maxlen = ch->init_maxlen;
 }
 EXPORT_SYMBOL(mISDN_clear_bchannel);
 
@@ -148,6 +158,33 @@ mISDN_freebchannel(struct bchannel *ch)
 }
 EXPORT_SYMBOL(mISDN_freebchannel);
 
+int
+mISDN_ctrl_bchannel(struct bchannel *bch, struct mISDN_ctrl_req *cq)
+{
+	int ret = 0;
+
+	switch (cq->op) {
+	case MISDN_CTRL_GETOP:
+		cq->op = MISDN_CTRL_RX_BUFFER;
+		break;
+	case MISDN_CTRL_RX_BUFFER:
+		if (cq->p2 > MISDN_CTRL_RX_SIZE_IGNORE)
+			bch->next_maxlen = cq->p2;
+		if (cq->p1 > MISDN_CTRL_RX_SIZE_IGNORE)
+			bch->next_minlen = cq->p1;
+		/* we return the old values */
+		cq->p1 = bch->minlen;
+		cq->p2 = bch->maxlen;
+		break;
+	default:
+		pr_info("mISDN unhandled control %x operation\n", cq->op);
+		ret = -EINVAL;
+		break;
+	}
+	return ret;
+}
+EXPORT_SYMBOL(mISDN_ctrl_bchannel);
+
 static inline u_int
 get_sapi_tei(u_char *p)
 {
@@ -197,7 +234,7 @@ recv_Echannel(struct dchannel *ech, struct dchannel *dch)
 EXPORT_SYMBOL(recv_Echannel);
 
 void
-recv_Bchannel(struct bchannel *bch, unsigned int id)
+recv_Bchannel(struct bchannel *bch, unsigned int id, bool force)
 {
 	struct mISDNhead *hh;
 
@@ -211,6 +248,9 @@ recv_Bchannel(struct bchannel *bch, unsigned int id)
 		dev_kfree_skb(bch->rx_skb);
 		bch->rx_skb = NULL;
 	} else {
+		if (test_bit(FLG_TRANSPARENT, &bch->Flags) &&
+		    (bch->rx_skb->len < bch->minlen) && !force)
+				return;
 		hh = mISDN_HEAD_P(bch->rx_skb);
 		hh->prim = PH_DATA_IND;
 		hh->id = id;
@@ -426,7 +466,7 @@ bchannel_get_rxbuf(struct bchannel *bch, int reqlen)
 				   bch->nr, reqlen, len);
 			if (test_bit(FLG_TRANSPARENT, &bch->Flags)) {
 				/* send what we have now and try a new buffer */
-				recv_Bchannel(bch, 0);
+				recv_Bchannel(bch, 0, true);
 			} else {
 				/* on HDLC we have to drop too big frames */
 				return -EMSGSIZE;
@@ -435,12 +475,25 @@ bchannel_get_rxbuf(struct bchannel *bch, int reqlen)
 			return len;
 		}
 	}
+	/* update current min/max length first */
+	if (unlikely(bch->maxlen != bch->next_maxlen))
+		bch->maxlen = bch->next_maxlen;
+	if (unlikely(bch->minlen != bch->next_minlen))
+		bch->minlen = bch->next_minlen;
 	if (unlikely(reqlen > bch->maxlen))
 		return -EMSGSIZE;
-	if (test_bit(FLG_TRANSPARENT, &bch->Flags))
-		len = reqlen;
-	else /* with HDLC we do not know the length yet */
+	if (test_bit(FLG_TRANSPARENT, &bch->Flags)) {
+		if (reqlen >= bch->minlen) {
+			len = reqlen;
+		} else {
+			len = 2 * bch->minlen;
+			if (len > bch->maxlen)
+				len = bch->maxlen;
+		}
+	} else {
+		/* with HDLC we do not know the length yet */
 		len = bch->maxlen;
+	}
 	bch->rx_skb = mI_alloc_skb(len, GFP_ATOMIC);
 	if (!bch->rx_skb) {
 		pr_warning("B%d receive no memory for %d bytes\n",
diff --git a/drivers/isdn/mISDN/l1oip_core.c b/drivers/isdn/mISDN/l1oip_core.c
index 0f88acf..db50f78 100644
--- a/drivers/isdn/mISDN/l1oip_core.c
+++ b/drivers/isdn/mISDN/l1oip_core.c
@@ -1420,7 +1420,7 @@ init_card(struct l1oip *hc, int pri, int bundle)
 		bch->nr = i + ch;
 		bch->slot = i + ch;
 		bch->debug = debug;
-		mISDN_initbchannel(bch, MAX_DATA_MEM);
+		mISDN_initbchannel(bch, MAX_DATA_MEM, 0);
 		bch->hw = hc;
 		bch->ch.send = handle_bmsg;
 		bch->ch.ctrl = l1oip_bctrl;