[PATCH v2 3/3] Bluetooth: coredump: Expose header size and end marker to drivers

[Zijun Hu]

To separate the coredump header and data far more easily, give a
vendor driver the option to pad its header to a fixed size, by
moving the header size limit and ending marker to coredump.h:

 - HCI_DEVCD_HDR_SIZE_MAX: the max header size
 - HCI_DEVCD_HDR_END_MARKER: the header-ending marker

No functional change intended.

Signed-off-by: Zijun Hu <zijun.hu@xxxxxxxxxxxxxxxx>
---
Previous version:
https://lore.kernel.org/all/20260713-btusb_prep_qcc2072-v2-2-bbcb651285f2@xxxxxxxxxxxxxxxx

Changes since previous version:
- Rename MAX_HCI_DEVCD_HDR_SIZE to HCI_DEVCD_HDR_SIZE_MAX
- Rename HCI_DEVCD_HDR_END to HCI_DEVCD_HDR_END_MARKER
- Improve the commit title and message
---
 include/net/bluetooth/coredump.h | 7 +++++++
 net/bluetooth/coredump.c         | 7 ++-----
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/include/net/bluetooth/coredump.h b/include/net/bluetooth/coredump.h
index ab85a6adfffd..1f071ab55416 100644
--- a/include/net/bluetooth/coredump.h
+++ b/include/net/bluetooth/coredump.h
@@ -3,16 +3,23 @@
  * Copyright (C) 2022 Google Corporation
  */
 
 #ifndef __COREDUMP_H
 #define __COREDUMP_H
 
 #define DEVCOREDUMP_TIMEOUT	msecs_to_jiffies(10000)	/* 10 sec */
 
+/*
+ * Max header size, shared by both the devcoredump core and
+ * the dmp_hdr() registered by driver via hci_devcd_register()
+ */
+#define HCI_DEVCD_HDR_SIZE_MAX	512
+#define HCI_DEVCD_HDR_END_MARKER	"--- Start dump ---\n"
+
 typedef void (*coredump_t)(struct hci_dev *hdev);
 typedef void (*dmp_hdr_t)(struct hci_dev *hdev, struct sk_buff *skb);
 typedef void (*notify_change_t)(struct hci_dev *hdev, int state);
 
 /* struct hci_devcoredump - Devcoredump state
  *
  * @supported: Indicates if FW dump collection is supported by driver
  * @state: Current state of dump collection
diff --git a/net/bluetooth/coredump.c b/net/bluetooth/coredump.c
index 913bbba559f8..5bee863bd6d2 100644
--- a/net/bluetooth/coredump.c
+++ b/net/bluetooth/coredump.c
@@ -29,18 +29,16 @@ struct hci_devcoredump_skb_pattern {
 #define hci_dmp_cb(skb)	((struct hci_devcoredump_skb_cb *)((skb)->cb))
 
 #define DBG_UNEXPECTED_STATE() \
 	bt_dev_dbg(hdev, \
 		   "Unexpected packet (%d) for state %s.", \
 		   hci_dmp_cb(skb)->pkt_type, \
 		   hci_devcd_state_name(hdev->dump.state))
 
-#define MAX_DEVCOREDUMP_HDR_SIZE	512	/* bytes */
-
 static int hci_devcd_update_hdr_state(char *buf, size_t size, int state)
 {
 	int len = 0;
 
 	if (!buf)
 		return 0;
 
 	len = scnprintf(buf, size, "Bluetooth devcoredump\nState: %d\n", state);
@@ -58,28 +56,27 @@ static int hci_devcd_update_state(struct hci_dev *hdev, int state)
 	hdev->dump.state = state;
 
 	return hci_devcd_update_hdr_state(hdev->dump.head,
 					  hdev->dump.alloc_size, state);
 }
 
 static int hci_devcd_mkheader(struct hci_dev *hdev, struct sk_buff *skb)
 {
-	char dump_start[] = "--- Start dump ---\n";
 	char hdr[80];
 	int hdr_len;
 
 	hdr_len = hci_devcd_update_hdr_state(hdr, sizeof(hdr),
 					     HCI_DEVCOREDUMP_IDLE);
 	skb_put_data(skb, hdr, hdr_len);
 
 	if (hdev->dump.dmp_hdr)
 		hdev->dump.dmp_hdr(hdev, skb);
 
-	skb_put_data(skb, dump_start, strlen(dump_start));
+	skb_put_data(skb, HCI_DEVCD_HDR_END_MARKER, strlen(HCI_DEVCD_HDR_END_MARKER));
 
 	return skb->len;
 }
 
 /* Do not call with hci_dev_lock since this calls driver code. */
 static void hci_devcd_notify(struct hci_dev *hdev, int state)
 {
 	if (hdev->dump.notify_change)
@@ -149,17 +146,17 @@ static bool hci_devcd_memset(struct hci_dev *hdev, u8 pattern, u32 len)
 
 /* Call with hci_dev_lock only. */
 static int hci_devcd_prepare(struct hci_dev *hdev, u32 dump_size)
 {
 	struct sk_buff *skb;
 	int dump_hdr_size;
 	int err = 0;
 
-	skb = alloc_skb(MAX_DEVCOREDUMP_HDR_SIZE, GFP_ATOMIC);
+	skb = alloc_skb(HCI_DEVCD_HDR_SIZE_MAX, GFP_ATOMIC);
 	if (!skb)
 		return -ENOMEM;
 
 	dump_hdr_size = hci_devcd_mkheader(hdev, skb);
 
 	if (hci_devcd_alloc(hdev, dump_hdr_size + dump_size)) {
 		err = -ENOMEM;
 		goto hdr_free;

-- 
2.34.1