[PATCH] USBATM: handle urbs containing partial cells

The receive logic has always assumed that urbs contain an integral
number of ATM cells, which is a bit naughty, though it never caused
any problems with bulk transfers.  Isochronous urbs spank us soundly
for this.  Fixed thanks to this patch, mostly by Stanislaw Gruszka.
Signed-off-by: Duncan Sands <baldrick@free.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/atm/usbatm.c

@@ -296,38 +296,30 @@ static inline struct usbatm_vcc_data *usbatm_find_vcc(struct usbatm_data *instan
 	return NULL;
 }
 
-static void usbatm_extract_cells(struct usbatm_data *instance,
-			       unsigned char *source, unsigned int avail_data)
+static void usbatm_extract_one_cell(struct usbatm_data *instance, unsigned char *source)
 {
-	struct usbatm_vcc_data *cached_vcc = NULL;
 	struct atm_vcc *vcc;
 	struct sk_buff *sarb;
-	unsigned int stride = instance->rx_channel.stride;
-	int vci, cached_vci = 0;
-	short vpi, cached_vpi = 0;
-	u8 pti;
-
-	for (; avail_data >= stride; avail_data -= stride, source += stride) {
-		vpi = ((source[0] & 0x0f) << 4)  | (source[1] >> 4);
-		vci = ((source[1] & 0x0f) << 12) | (source[2] << 4) | (source[3] >> 4);
-		pti = ((source[3] & 0xe) >> 1);
+	short vpi = ((source[0] & 0x0f) << 4)  | (source[1] >> 4);
+	int vci = ((source[1] & 0x0f) << 12) | (source[2] << 4) | (source[3] >> 4);
+	u8 pti = ((source[3] & 0xe) >> 1);
 
 	vdbg("%s: vpi %hd, vci %d, pti %d", __func__, vpi, vci, pti);
 
-		if ((vci != cached_vci) || (vpi != cached_vpi)) {
-			cached_vpi = vpi;
-			cached_vci = vci;
+	if ((vci != instance->cached_vci) || (vpi != instance->cached_vpi)) {
+		instance->cached_vpi = vpi;
+		instance->cached_vci = vci;
 
-			cached_vcc = usbatm_find_vcc(instance, vpi, vci);
+		instance->cached_vcc = usbatm_find_vcc(instance, vpi, vci);
 
-			if (!cached_vcc)
+		if (!instance->cached_vcc)
 			atm_rldbg(instance, "%s: unknown vpi/vci (%hd/%d)!\n", __func__, vpi, vci);
 	}
 
-		if (!cached_vcc)
-			continue;
+	if (!instance->cached_vcc)
+		return;
 
-		vcc = cached_vcc->vcc;
+	vcc = instance->cached_vcc->vcc;
 
 	/* OAM F5 end-to-end */
 	if (pti == ATM_PTI_E2EF5) {
@@ -335,10 +327,10 @@ static void usbatm_extract_cells(struct usbatm_data *instance,
 			atm_warn(instance, "%s: OAM not supported (vpi %d, vci %d)!\n",
 				__func__, vpi, vci);
 		atomic_inc(&vcc->stats->rx_err);
-			continue;
+		return;
 	}
 
-		sarb = cached_vcc->sarb;
+	sarb = instance->cached_vcc->sarb;
 
 	if (sarb->tail + ATM_CELL_PAYLOAD > sarb->end) {
 		atm_rldbg(instance, "%s: buffer overrun (sarb->len %u, vcc: 0x%p)!\n",
@@ -415,6 +407,47 @@ static void usbatm_extract_cells(struct usbatm_data *instance,
 	out:
 		skb_trim(sarb, 0);
 	}
+}
+
+static void usbatm_extract_cells(struct usbatm_data *instance,
+		unsigned char *source, unsigned int avail_data)
+{
+	unsigned int stride = instance->rx_channel.stride;
+	unsigned int buf_usage = instance->buf_usage;
+
+	/* extract cells from incoming data, taking into account that
+	 * the length of avail data may not be a multiple of stride */
+
+	if (buf_usage > 0) {
+		/* we have a partially received atm cell */
+		unsigned char *cell_buf = instance->cell_buf;
+		unsigned int space_left = stride - buf_usage;
+
+		UDSL_ASSERT(buf_usage <= stride);
+
+		if (avail_data >= space_left) {
+			/* add new data and process cell */
+			memcpy(cell_buf + buf_usage, source, space_left);
+			source += space_left;
+			avail_data -= space_left;
+			usbatm_extract_one_cell(instance, cell_buf);
+			instance->buf_usage = 0;
+		} else {
+			/* not enough data to fill the cell */
+			memcpy(cell_buf + buf_usage, source, avail_data);
+			instance->buf_usage = buf_usage + avail_data;
+			return;
+		}
+	}
+
+	for (; avail_data >= stride; avail_data -= stride, source += stride)
+		usbatm_extract_one_cell(instance, source);
+
+	if (avail_data > 0) {
+		/* length was not a multiple of stride -
+		 * save remaining data for next call */
+		memcpy(instance->cell_buf, source, avail_data);
+		instance->buf_usage = avail_data;
 	}
 }
 
@@ -496,16 +529,40 @@ static void usbatm_rx_process(unsigned long data)
 		vdbg("%s: processing urb 0x%p", __func__, urb);
 
 		if (usb_pipeisoc(urb->pipe)) {
+			unsigned char *merge_start = NULL;
+			unsigned int merge_length = 0;
+			const unsigned int packet_size = instance->rx_channel.packet_size;
 			int i;
-			for (i = 0; i < urb->number_of_packets; i++)
-				if (!urb->iso_frame_desc[i].status)
-					usbatm_extract_cells(instance,
-							     (u8 *)urb->transfer_buffer + urb->iso_frame_desc[i].offset,
-							     urb->iso_frame_desc[i].actual_length);
+
+			for (i = 0; i < urb->number_of_packets; i++) {
+				if (!urb->iso_frame_desc[i].status) {
+					unsigned int actual_length = urb->iso_frame_desc[i].actual_length;
+
+					UDSL_ASSERT(actual_length <= packet_size);
+
+					if (!merge_length)
+						merge_start = (unsigned char *)urb->transfer_buffer + urb->iso_frame_desc[i].offset;
+					merge_length += actual_length;
+					if (merge_length && (actual_length < packet_size)) {
+						usbatm_extract_cells(instance, merge_start, merge_length);
+						merge_length = 0;
 					}
-		else
+				} else {
+					atm_rldbg(instance, "%s: status %d in frame %d!\n", __func__, urb->status, i);
+					if (merge_length)
+						usbatm_extract_cells(instance, merge_start, merge_length);
+					merge_length = 0;
+					instance->buf_usage = 0;
+				}
+			}
+
+			if (merge_length)
+				usbatm_extract_cells(instance, merge_start, merge_length);
+		} else
 			if (!urb->status)
 				usbatm_extract_cells(instance, urb->transfer_buffer, urb->actual_length);
+			else
+				instance->buf_usage = 0;
 
 		if (usbatm_submit_urb(urb))
 			return;
@@ -797,6 +854,9 @@ static int usbatm_atm_open(struct atm_vcc *vcc)
 	vcc->dev_data = new;
 
 	tasklet_disable(&instance->rx_channel.tasklet);
+	instance->cached_vcc = new;
+	instance->cached_vpi = vpi;
+	instance->cached_vci = vci;
 	list_add(&new->list, &instance->vcc_list);
 	tasklet_enable(&instance->rx_channel.tasklet);
 
@@ -836,6 +896,11 @@ static void usbatm_atm_close(struct atm_vcc *vcc)
 	down(&instance->serialize);	/* vs self, usbatm_atm_open, usbatm_usb_disconnect */
 
 	tasklet_disable(&instance->rx_channel.tasklet);
+	if (instance->cached_vcc == vcc_data) {
+		instance->cached_vcc = NULL;
+		instance->cached_vpi = ATM_VPI_UNSPEC;
+		instance->cached_vci = ATM_VCI_UNSPEC;
+	}
 	list_del(&vcc_data->list);
 	tasklet_enable(&instance->rx_channel.tasklet);
 
@@ -1146,6 +1211,16 @@ int usbatm_usb_probe(struct usb_interface *intf, const struct usb_device_id *id,
 		     __func__, urb->transfer_buffer, urb->transfer_buffer_length, urb);
 	}
 
+	instance->cached_vpi = ATM_VPI_UNSPEC;
+	instance->cached_vci = ATM_VCI_UNSPEC;
+	instance->cell_buf = kmalloc(instance->rx_channel.stride, GFP_KERNEL);
+
+	if (!instance->cell_buf) {
+		dev_err(dev, "%s: no memory for cell buffer!\n", __func__);
+		error = -ENOMEM;
+		goto fail_unbind;
+	}
+
 	if (!(instance->flags & UDSL_SKIP_HEAVY_INIT) && driver->heavy_init) {
 		error = usbatm_heavy_init(instance);
 	} else {
@@ -1165,6 +1240,8 @@ int usbatm_usb_probe(struct usb_interface *intf, const struct usb_device_id *id,
 	if (instance->driver->unbind)
 		instance->driver->unbind(instance, intf);
  fail_free:
+	kfree(instance->cell_buf);
+
 	for (i = 0; i < num_rcv_urbs + num_snd_urbs; i++) {
 		if (instance->urbs[i])
 			kfree(instance->urbs[i]->transfer_buffer);
@@ -1236,6 +1313,8 @@ void usbatm_usb_disconnect(struct usb_interface *intf)
 		usb_free_urb(instance->urbs[i]);
 	}
 
+	kfree(instance->cell_buf);
+
 	/* ATM finalize */
 	if (instance->atm_dev)
 		atm_dev_deregister(instance->atm_dev);

drivers/usb/atm/usbatm.h

@@ -187,6 +187,13 @@ struct usbatm_data {
 	struct sk_buff_head sndqueue;
 	struct sk_buff *current_skb;	/* being emptied */
 
+	struct usbatm_vcc_data *cached_vcc;
+	int cached_vci;
+	short cached_vpi;
+
+	unsigned char *cell_buf;	/* holds partial rx cell */
+	unsigned int buf_usage;
+
 	struct urb *urbs[0];
 };