Subject: Re: [PATCH] net/usb: Add Samsung Kalmia driver for Samsung GT-B3730

From: Oliver Neukum <[email-masked]>
Date: Tue, 14 Jun 2011 10:49:39 +0200

Am Samstag, 11. Juni 2011, 23:55:18 schrieb Marius B. Kotsbak:

Hi,

thanks for writing a new driver. My comments are included in the quote.

	Regards
		Oliver

> +static int
> +kalmia_init_and_get_ethernet_addr(struct usbnet *dev, u8 *ethernet_addr)
> +{
> +	char init_msg_1[] =
> +		{ 0x57, 0x50, 0x04, 0x00, 0x00, 0x00, 0x00, 0x20, 0x00, 0x00,
> +		0x00, 0x00 };
> +	char init_msg_2[] =
> +		{ 0x57, 0x50, 0x04, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0xf4,
> +		0x00, 0x00 };
> +	char receive_buf[28];

You are doing DMA on the stack. This will fail on some architectures.

> +	int status;
> +
> +	status = kalmia_send_init_packet(dev, init_msg_1, sizeof(init_msg_1)
> +		/ sizeof(init_msg_1[0]), receive_buf, 24);
> +	if (status != 0)
> +		return status;
> +
> +	status = kalmia_send_init_packet(dev, init_msg_2, sizeof(init_msg_2)
> +		/ sizeof(init_msg_2[0]), receive_buf, 28);
> +	if (status != 0)
> +		return status;
> +
> +	memcpy(ethernet_addr, receive_buf + 10, ETH_ALEN);
> +
> +	return status;
> +}
> +
> +static int
> +kalmia_bind(struct usbnet *dev, struct usb_interface *intf)
> +{
> +	u8 status;
> +	u8 ethernet_addr[ETH_ALEN];
> +
> +	/* Don't bind to AT command interface */
> +	if (intf->cur_altsetting->desc.bInterfaceClass != USB_CLASS_VENDOR_SPEC)
> +		return -EINVAL;
> +
> +	dev->in = usb_rcvbulkpipe(dev->udev, 0x81 & USB_ENDPOINT_NUMBER_MASK);
> +	dev->out = usb_sndbulkpipe(dev->udev, 0x02 & USB_ENDPOINT_NUMBER_MASK);
> +	dev->status = NULL;
> +
> +	dev->net->hard_header_len += KALMIA_HEADER_LENGTH;
> +	dev->hard_mtu = 1400;
> +	dev->rx_urb_size = dev->hard_mtu * 10; // Found as optimal after testing
> +
> +	status = kalmia_init_and_get_ethernet_addr(dev, ethernet_addr);
> +
> +	if (status < 0) {
> +		usb_set_intfdata(intf, NULL);
> +		usb_driver_release_interface(driver_of(intf), intf);
> +		return status;

Why are you doing this? What is to be undone?

> +	}
> +
> +	memcpy(dev->net->dev_addr, ethernet_addr, ETH_ALEN);
> +	memcpy(dev->net->perm_addr, ethernet_addr, ETH_ALEN);
> +
> +	return status;
> +}
> +
> +static struct sk_buff *
> +kalmia_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
> +{
> +	struct sk_buff *skb2 = NULL;
> +	u16 content_len;
> +	unsigned char *header_start;
> +	unsigned char ether_type_1, ether_type_2;
> +	u8 remainder, padlen = 0;
> +
> +	if (!skb_cloned(skb)) {
> +		int headroom = skb_headroom(skb);
> +		int tailroom = skb_tailroom(skb);
> +
> +		if ((tailroom >= KALMIA_ALIGN_SIZE) && (headroom
> +			>= KALMIA_HEADER_LENGTH))
> +			goto done;
> +
> +		if ((headroom + tailroom) > (KALMIA_HEADER_LENGTH
> +			+ KALMIA_ALIGN_SIZE)) {
> +			skb->data = memmove(skb->head + KALMIA_HEADER_LENGTH,
> +				skb->data, skb->len);
> +			skb_set_tail_pointer(skb, skb->len);
> +			goto done;
> +		}
> +	}
> +
> +	skb2 = skb_copy_expand(skb, KALMIA_HEADER_LENGTH,
> +		KALMIA_ALIGN_SIZE, flags);
> +	if (!skb2)
> +		return NULL;
> +
> +	dev_kfree_skb_any(skb);
> +	skb = skb2;
> +
> +	done: header_start = skb_push(skb, KALMIA_HEADER_LENGTH);

coding style

> +	ether_type_1 = header_start[KALMIA_HEADER_LENGTH + 12];
> +	ether_type_2 = header_start[KALMIA_HEADER_LENGTH + 13];
> +
> +	netdev_dbg(dev->net, "Sending etherType: %02x%02x", ether_type_1,
> +		ether_type_2);
> +
> +	/* According to empiric data for data packages */
> +	header_start[0] = 0x57;
> +	header_start[1] = 0x44;
> +	content_len = skb->len - KALMIA_HEADER_LENGTH;
> +	header_start[2] = (content_len & 0xff); /* low byte */
> +	header_start[3] = (content_len >> 8); /* high byte */

Please use an endianness macro

> +	header_start[4] = ether_type_1;
> +	header_start[5] = ether_type_2;
> +
> +	/* Align to 4 bytes by padding with zeros */
> +	remainder = skb->len % KALMIA_ALIGN_SIZE;
> +	if (remainder > 0) {
> +		padlen = KALMIA_ALIGN_SIZE - remainder;
> +		memset(skb_put(skb, padlen), 0, padlen);
> +	}
> +
> +	netdev_dbg(
> +		dev->net,
> +		"Sending package with length %i and padding %i. Header: %02x:%02x:%02x:%02x:%02x:%02x.",
> +		content_len, padlen, header_start[0], header_start[1],
> +		header_start[2], header_start[3], header_start[4],
> +		header_start[5]);
> +
> +	return skb;
> +}
> +
> +static int
> +kalmia_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
> +{
> +	/*
> +	 * Our task here is to strip off framing, leaving skb with one
> +	 * data frame for the usbnet framework code to process.
> +	 */
> +	const u8 HEADER_END_OF_USB_PACKET[] =
> +		{ 0x57, 0x5a, 0x00, 0x00, 0x08, 0x00 };
> +	const u8 EXPECTED_UNKNOWN_HEADER_1[] =
> +		{ 0x57, 0x43, 0x1e, 0x00, 0x15, 0x02 };
> +	const u8 EXPECTED_UNKNOWN_HEADER_2[] =
> +		{ 0x57, 0x50, 0x0e, 0x00, 0x00, 0x00 };

What does the compiler do to this declaration?

> +	u8 i = 0;

Why not int?

> +
> +	/* incomplete header? */
> +	if (skb->len < KALMIA_HEADER_LENGTH)
> +		return 0;
> +
> +	do {
> +		struct sk_buff *skb2 = NULL;
> +		u8 *header_start;
> +		u16 usb_packet_length, ether_packet_length;
> +		int is_last;
> +
> +		header_start = skb->data;
> +
> +		if (unlikely(header_start[0] != 0x57 || header_start[1] != 0x44)) {
> +			if (!memcmp(header_start, EXPECTED_UNKNOWN_HEADER_1,
> +				sizeof(EXPECTED_UNKNOWN_HEADER_1)) || !memcmp(
> +				header_start, EXPECTED_UNKNOWN_HEADER_2,
> +				sizeof(EXPECTED_UNKNOWN_HEADER_2))) {
> +				netdev_dbg(
> +					dev->net,
> +					"Received expected unknown frame header: %02x:%02x:%02x:%02x:%02x:%02x. Package length: %i\n",
> +					header_start[0], header_start[1],
> +					header_start[2], header_start[3],
> +					header_start[4], header_start[5],
> +					skb->len - KALMIA_HEADER_LENGTH);
> +			}
> +			else {
> +				netdev_err(
> +					dev->net,
> +					"Received unknown frame header: %02x:%02x:%02x:%02x:%02x:%02x. Package length: %i\n",
> +					header_start[0], header_start[1],
> +					header_start[2], header_start[3],
> +					header_start[4], header_start[5],
> +					skb->len - KALMIA_HEADER_LENGTH);
> +				return 0;
> +			}
> +		}
> +		else
> +			netdev_dbg(
> +				dev->net,
> +				"Received header: %02x:%02x:%02x:%02x:%02x:%02x. Package length: %i\n",
> +				header_start[0], header_start[1], header_start[2],
> +				header_start[3], header_start[4], header_start[5],
> +				skb->len - KALMIA_HEADER_LENGTH);
> +
> +		/* subtract start header and end header */
> +		usb_packet_length = skb->len - (2 * KALMIA_HEADER_LENGTH);
> +		ether_packet_length = header_start[2] + (header_start[3] << 8);

Please use an endianness macro

> +		skb_pull(skb, KALMIA_HEADER_LENGTH);
> +
> +		/* Some small packets misses end marker */
> +		if (usb_packet_length < ether_packet_length) {
> +			ether_packet_length = usb_packet_length
> +				+ KALMIA_HEADER_LENGTH;
> +			is_last = true;
> +		}
> +		else {
> +			netdev_dbg(dev->net, "Correct package length #%i", i
> +				+ 1);
> +
> +			is_last = (memcmp(skb->data + ether_packet_length,
> +				HEADER_END_OF_USB_PACKET,
> +				sizeof(HEADER_END_OF_USB_PACKET)) == 0);
> +			if (!is_last) {
> +				header_start = skb->data + ether_packet_length;
> +				netdev_dbg(
> +					dev->net,
> +					"End header: %02x:%02x:%02x:%02x:%02x:%02x. Package length: %i\n",
> +					header_start[0], header_start[1],
> +					header_start[2], header_start[3],
> +					header_start[4], header_start[5],
> +					skb->len - KALMIA_HEADER_LENGTH);
> +			}
> +		}
> +
> +		if (is_last) {
> +			skb2 = skb;
> +		}
> +		else {
> +			skb2 = skb_clone(skb, GFP_ATOMIC);
> +			if (unlikely(!skb2))
> +				return 0;
> +		}
> +
> +		skb_trim(skb2, ether_packet_length);
> +
> +		if (is_last) {
> +			return 1;
> +		}
> +		else {
> +			usbnet_skb_return(dev, skb2);
> +			skb_pull(skb, ether_packet_length);
> +		}
> +
> +		i++;
> +	}
> +	while (skb->len);
> +
> +	return 1;
> +}
> +
> +static const struct driver_info kalmia_info = {
> +	.description = "Samsung Kalmia LTE USB dongle",
> +	.flags = FLAG_WWAN,
> +	.bind = kalmia_bind,
> +	.rx_fixup = kalmia_rx_fixup,
> +	.tx_fixup = kalmia_tx_fixup
> +};
> +
> +/*-------------------------------------------------------------------------*/
> +
> +static const struct usb_device_id products[] = {
> +	/* The unswitched USB ID, to get the module auto loaded: */
> +	{ USB_DEVICE(0x04e8, 0x689a) },

Why is this needed? Doesn't the switch trigger an autoload?

> +	/* The stick swithed into modem (by e.g. usb_modeswitch): */
> +	{ USB_DEVICE(0x04e8, 0x6889),
> +		.driver_info = (unsigned long) &kalmia_info, },
> +	{ /* EMPTY == end of list */} };
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to [email-masked]
More majordomo info at  http://vger.kernel.org/majordomo-info.html