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Groups > linux.kernel > #1461581 > unrolled thread

[RFC 4/7] Bluetooth: hci_uart: Add support for word alignment

Started bySebastian Reichel <sre@kernel.org>
First post2016-08-13 05:20 +0200
Last post2016-08-16 10:00 +0200
Articles 4 — 3 participants

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  [RFC 4/7] Bluetooth: hci_uart: Add support for word alignment Sebastian Reichel <sre@kernel.org> - 2016-08-13 05:20 +0200
    Re: [RFC 4/7] Bluetooth: hci_uart: Add support for word alignment Pavel Machek <pavel@ucw.cz> - 2016-08-14 11:00 +0200
    Re: [RFC 4/7] Bluetooth: hci_uart: Add support for word alignment Marcel Holtmann <marcel@holtmann.org> - 2016-08-16 09:10 +0200
      Re: [RFC 4/7] Bluetooth: hci_uart: Add support for word alignment Sebastian Reichel <sre@kernel.org> - 2016-08-16 10:00 +0200

#1461581 — [RFC 4/7] Bluetooth: hci_uart: Add support for word alignment

FromSebastian Reichel <sre@kernel.org>
Date2016-08-13 05:20 +0200
Subject[RFC 4/7] Bluetooth: hci_uart: Add support for word alignment
Message-ID<s5xEm-2xg-21@gated-at.bofh.it>
This will be used by Nokia's H4+ protocol, which
adds padding to packets to reach word alignment.
---
 drivers/bluetooth/hci_h4.c   | 10 ++++++++++
 drivers/bluetooth/hci_uart.h |  1 +
 2 files changed, 11 insertions(+)

diff --git a/drivers/bluetooth/hci_h4.c b/drivers/bluetooth/hci_h4.c
index 635597b6e168..a934e4eb692b 100644
--- a/drivers/bluetooth/hci_h4.c
+++ b/drivers/bluetooth/hci_h4.c
@@ -253,11 +253,21 @@ struct sk_buff *h4_recv_buf(struct hci_dev *hdev, struct sk_buff *skb,
 			}
 
 			if (!dlen) {
+				if ((&pkts[i])->wordaligned && !(skb->len % 2)) {
+					buffer++;
+					count--;
+				}
+
 				/* No more data, complete frame */
 				(&pkts[i])->recv(hdev, skb);
 				skb = NULL;
 			}
 		} else {
+			if ((&pkts[i])->wordaligned && !(skb->len % 2)) {
+				buffer++;
+				count--;
+			}
+
 			/* Complete frame */
 			(&pkts[i])->recv(hdev, skb);
 			skb = NULL;
diff --git a/drivers/bluetooth/hci_uart.h b/drivers/bluetooth/hci_uart.h
index 839bad1d8152..a7d67aec3632 100644
--- a/drivers/bluetooth/hci_uart.h
+++ b/drivers/bluetooth/hci_uart.h
@@ -121,6 +121,7 @@ struct h4_recv_pkt {
 	u8  loff;	/* Data length offset in header */
 	u8  lsize;	/* Data length field size */
 	u16 maxlen;	/* Max overall packet length */
+	bool wordaligned;	/* packets are word aligned */
 	int (*recv)(struct hci_dev *hdev, struct sk_buff *skb);
 };
 
-- 
2.8.1

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#1461716

FromPavel Machek <pavel@ucw.cz>
Date2016-08-14 11:00 +0200
Message-ID<s5ZqW-5AD-13@gated-at.bofh.it>
In reply to#1461581
On Sat 2016-08-13 05:14:35, Sebastian Reichel wrote:
> This will be used by Nokia's H4+ protocol, which
> adds padding to packets to reach word alignment.

Add a sign-off.

Acked-by: Pavel Machek <pavel@ucw.cz>

Thanks,
							Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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#1463468

FromMarcel Holtmann <marcel@holtmann.org>
Date2016-08-16 09:10 +0200
Message-ID<s6GFz-8pe-13@gated-at.bofh.it>
In reply to#1461581
Hi Sebatian,

> This will be used by Nokia's H4+ protocol, which
> adds padding to packets to reach word alignment.
> ---
> drivers/bluetooth/hci_h4.c   | 10 ++++++++++
> drivers/bluetooth/hci_uart.h |  1 +
> 2 files changed, 11 insertions(+)
> 
> diff --git a/drivers/bluetooth/hci_h4.c b/drivers/bluetooth/hci_h4.c
> index 635597b6e168..a934e4eb692b 100644
> --- a/drivers/bluetooth/hci_h4.c
> +++ b/drivers/bluetooth/hci_h4.c
> @@ -253,11 +253,21 @@ struct sk_buff *h4_recv_buf(struct hci_dev *hdev, struct sk_buff *skb,
> 			}
> 
> 			if (!dlen) {
> +				if ((&pkts[i])->wordaligned && !(skb->len % 2)) {
> +					buffer++;
> +					count--;
> +				}
> +
> 				/* No more data, complete frame */
> 				(&pkts[i])->recv(hdev, skb);
> 				skb = NULL;
> 			}
> 		} else {
> +			if ((&pkts[i])->wordaligned && !(skb->len % 2)) {
> +				buffer++;
> +				count--;
> +			}
> +
> 			/* Complete frame */
> 			(&pkts[i])->recv(hdev, skb);
> 			skb = NULL;
> diff --git a/drivers/bluetooth/hci_uart.h b/drivers/bluetooth/hci_uart.h
> index 839bad1d8152..a7d67aec3632 100644
> --- a/drivers/bluetooth/hci_uart.h
> +++ b/drivers/bluetooth/hci_uart.h
> @@ -121,6 +121,7 @@ struct h4_recv_pkt {
> 	u8  loff;	/* Data length offset in header */
> 	u8  lsize;	/* Data length field size */
> 	u16 maxlen;	/* Max overall packet length */
> +	bool wordaligned;	/* packets are word aligned */

I wonder if not a u8 align would be a way better choice here. We set it to 1 for all existing packet types. And the Nokia driver can use 2 here.

> 	int (*recv)(struct hci_dev *hdev, struct sk_buff *skb);

Regards

Marcel

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#1463516

FromSebastian Reichel <sre@kernel.org>
Date2016-08-16 10:00 +0200
Message-ID<s6HrY-fU-27@gated-at.bofh.it>
In reply to#1463468

[Multipart message — attachments visible in raw view] — view raw

Hi Marcel,

On Tue, Aug 16, 2016 at 09:05:19AM +0200, Marcel Holtmann wrote:
> Hi Sebatian,
> 
> > This will be used by Nokia's H4+ protocol, which
> > adds padding to packets to reach word alignment.
> > ---
> > drivers/bluetooth/hci_h4.c   | 10 ++++++++++
> > drivers/bluetooth/hci_uart.h |  1 +
> > 2 files changed, 11 insertions(+)
> > 
> > diff --git a/drivers/bluetooth/hci_h4.c b/drivers/bluetooth/hci_h4.c
> > index 635597b6e168..a934e4eb692b 100644
> > --- a/drivers/bluetooth/hci_h4.c
> > +++ b/drivers/bluetooth/hci_h4.c
> > @@ -253,11 +253,21 @@ struct sk_buff *h4_recv_buf(struct hci_dev *hdev, struct sk_buff *skb,
> > 			}
> > 
> > 			if (!dlen) {
> > +				if ((&pkts[i])->wordaligned && !(skb->len % 2)) {
> > +					buffer++;
> > +					count--;
> > +				}
> > +
> > 				/* No more data, complete frame */
> > 				(&pkts[i])->recv(hdev, skb);
> > 				skb = NULL;
> > 			}
> > 		} else {
> > +			if ((&pkts[i])->wordaligned && !(skb->len % 2)) {
> > +				buffer++;
> > +				count--;
> > +			}
> > +
> > 			/* Complete frame */
> > 			(&pkts[i])->recv(hdev, skb);
> > 			skb = NULL;
> > diff --git a/drivers/bluetooth/hci_uart.h b/drivers/bluetooth/hci_uart.h
> > index 839bad1d8152..a7d67aec3632 100644
> > --- a/drivers/bluetooth/hci_uart.h
> > +++ b/drivers/bluetooth/hci_uart.h
> > @@ -121,6 +121,7 @@ struct h4_recv_pkt {
> > 	u8  loff;	/* Data length offset in header */
> > 	u8  lsize;	/* Data length field size */
> > 	u16 maxlen;	/* Max overall packet length */
> > +	bool wordaligned;	/* packets are word aligned */
> 
> I wonder if not a u8 align would be a way better choice here. We
> set it to 1 for all existing packet types. And the Nokia driver
> can use 2 here.

Sounds less hacky than my approach. Also it made me notice, that my
code is not safe, since the buffer size is not checked. I will use
u8 align and fix the buffer size check.

-- Sebastian

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