diff mbox series

[QUESTION] bluetooth: Remove duplicated h4_recv_buf() in header

Message ID 2b612e2c1f4fa697b47b5dd9b72f1949d7c206f5.1742324401.git.calvin@wbinvd.org (mailing list archive)
State New
Headers show
Series [QUESTION] bluetooth: Remove duplicated h4_recv_buf() in header | expand

Commit Message

Calvin Owens March 18, 2025, 7:31 p.m. UTC 
Hello all,

In the course of other debugging, I've discovered that h4_recv_buf() is
almost completely duplicated in an inline header definiton, and I don't
understand why.

I'd like to clean this up: see the patch below for an explanation.

Does anybody who was around at the time remember any more details about
this? Or failing that, perhaps somebody with access to the bpa10x
hardware can test it with the core function?

Thanks,
Calvin

---8<---
From: Calvin Owens <calvin@wbinvd.org>
Subject: [PATCH] bluetooth: Remove duplicated h4_recv_buf() in header

The "h4_recv.h" header contains a duplicate h4_recv_buf() that is nearly
but not quite identical to the h4_recv_buf() in hci_h4.c.

This duplicated header was added in commit 07eb96a5a7b0 ("Bluetooth:
bpa10x: Use separate h4_recv_buf helper"). Unfortunately, there was no
discussion about it on the list at the time:

    https://lore.kernel.org/all/20180320181855.37297-1-marcel@holtmann.org/
    https://lore.kernel.org/all/20180324091954.73229-2-marcel@holtmann.org/

This is the diff between the two implementations as they exist today:

    --- /home/calvinow/orig.c	2025-03-10 14:43:18.383882623 -0700
    +++ /home/calvinow/copy.c	2025-03-10 14:42:57.109953576 -0700
    @@ -1,117 +1,100 @@
     {
    -	struct hci_uart *hu = hci_get_drvdata(hdev);
    -	u8 alignment = hu->alignment ? hu->alignment : 1;
    -
     	/* Check for error from previous call */
     	if (IS_ERR(skb))
     		skb = NULL;

     	while (count) {
     		int i, len;

    -		/* remove padding bytes from buffer */
    -		for (; hu->padding && count > 0; hu->padding--) {
    -			count--;
    -			buffer++;
    -		}
    -		if (!count)
    -			break;
    -
     		if (!skb) {
     			for (i = 0; i < pkts_count; i++) {
     				if (buffer[0] != (&pkts[i])->type)
     					continue;

     				skb = bt_skb_alloc((&pkts[i])->maxlen,
     						   GFP_ATOMIC);
     				if (!skb)
     					return ERR_PTR(-ENOMEM);

     				hci_skb_pkt_type(skb) = (&pkts[i])->type;
     				hci_skb_expect(skb) = (&pkts[i])->hlen;
     				break;
     			}

     			/* Check for invalid packet type */
     			if (!skb)
     				return ERR_PTR(-EILSEQ);

     			count -= 1;
     			buffer += 1;
     		}

     		len = min_t(uint, hci_skb_expect(skb) - skb->len, count);
     		skb_put_data(skb, buffer, len);

     		count -= len;
     		buffer += len;

     		/* Check for partial packet */
     		if (skb->len < hci_skb_expect(skb))
     			continue;

     		for (i = 0; i < pkts_count; i++) {
     			if (hci_skb_pkt_type(skb) == (&pkts[i])->type)
     				break;
     		}

     		if (i >= pkts_count) {
     			kfree_skb(skb);
     			return ERR_PTR(-EILSEQ);
     		}

     		if (skb->len == (&pkts[i])->hlen) {
     			u16 dlen;

     			switch ((&pkts[i])->lsize) {
     			case 0:
     				/* No variable data length */
     				dlen = 0;
     				break;
     			case 1:
     				/* Single octet variable length */
     				dlen = skb->data[(&pkts[i])->loff];
     				hci_skb_expect(skb) += dlen;

     				if (skb_tailroom(skb) < dlen) {
     					kfree_skb(skb);
     					return ERR_PTR(-EMSGSIZE);
     				}
     				break;
     			case 2:
     				/* Double octet variable length */
     				dlen = get_unaligned_le16(skb->data +
     							  (&pkts[i])->loff);
     				hci_skb_expect(skb) += dlen;

     				if (skb_tailroom(skb) < dlen) {
     					kfree_skb(skb);
     					return ERR_PTR(-EMSGSIZE);
     				}
     				break;
     			default:
     				/* Unsupported variable length */
     				kfree_skb(skb);
     				return ERR_PTR(-EILSEQ);
     			}

     			if (!dlen) {
    -				hu->padding = (skb->len + 1) % alignment;
    -				hu->padding = (alignment - hu->padding) % alignment;
    -
     				/* No more data, complete frame */
     				(&pkts[i])->recv(hdev, skb);
     				skb = NULL;
     			}
     		} else {
    -			hu->padding = (skb->len + 1) % alignment;
    -			hu->padding = (alignment - hu->padding) % alignment;
    -
     			/* Complete frame */
     			(&pkts[i])->recv(hdev, skb);
     			skb = NULL;
     		}
     	}

     	return skb;
     }

It seems fairly obvious from the above that, if alignment is one,
hu->padding is always zero, and in that case the two functions behave
strictly identically.

Since that is the case for every driver except hci_nokia, clean this up
and let them use the core function. I've done some light testing on
btnxpuart, so far everything seems to work.

I would love to eliminate the duplicate function entirely, but I don't
have access to hardware for bpa10x. Since bpa10x breaking was the
original justification for the change, I've left it there for now. I'm
hoping somebody else can shed more light on this.

Cc: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Calvin Owens <calvin@wbinvd.org>
---
 drivers/bluetooth/btmtksdio.c | 2 +-
 drivers/bluetooth/btmtkuart.c | 2 +-
 drivers/bluetooth/btnxpuart.c | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/drivers/bluetooth/btmtksdio.c b/drivers/bluetooth/btmtksdio.c
index bd5464bde174..47d1073fb4a4 100644
--- a/drivers/bluetooth/btmtksdio.c
+++ b/drivers/bluetooth/btmtksdio.c
@@ -29,7 +29,7 @@ 
 #include <net/bluetooth/bluetooth.h>
 #include <net/bluetooth/hci_core.h>
 
-#include "h4_recv.h"
+#include "hci_uart.h"
 #include "btmtk.h"
 
 #define VERSION "0.1"
diff --git a/drivers/bluetooth/btmtkuart.c b/drivers/bluetooth/btmtkuart.c
index c97e260fcb0c..aeb111a0f242 100644
--- a/drivers/bluetooth/btmtkuart.c
+++ b/drivers/bluetooth/btmtkuart.c
@@ -27,7 +27,7 @@ 
 #include <net/bluetooth/bluetooth.h>
 #include <net/bluetooth/hci_core.h>
 
-#include "h4_recv.h"
+#include "hci_uart.h"
 #include "btmtk.h"
 
 #define VERSION "0.2"
diff --git a/drivers/bluetooth/btnxpuart.c b/drivers/bluetooth/btnxpuart.c
index aa5ec1d444a9..e6db563088cb 100644
--- a/drivers/bluetooth/btnxpuart.c
+++ b/drivers/bluetooth/btnxpuart.c
@@ -21,7 +21,7 @@ 
 #include <net/bluetooth/bluetooth.h>
 #include <net/bluetooth/hci_core.h>
 
-#include "h4_recv.h"
+#include "hci_uart.h"
 
 #define MANUFACTURER_NXP		37