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Message-ID: <20251114150738.32426-9-damien.riegel@silabs.com>
Date: Fri, 14 Nov 2025 10:07:34 -0500
From: Damien Riégel <damien.riegel@...abs.com>
To: greybus-dev@...ts.linaro.org, Johan Hovold <johan@...nel.org>,
Alex Elder <elder@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
linux-kernel@...r.kernel.org
Cc: Silicon Labs Kernel Team <linux-devel@...abs.com>,
Damien Riégel <damien.riegel@...abs.com>
Subject: [RFC PATCH v2 08/12] greybus: cpc: add and validate sequence numbers
The first step in making the CPC header actually do something is to add
the sequence number to outgoing messages and validate that incoming
frames are received in order.
At this stage, the driver doesn't send standalone acks, so if a message
with Sequence X is received, the remote will not be acknowledged until a
message targeting that CPort comes from the Greybus layer. Only then the
driver will ack with acknowledgedment number of X + 1.
Signed-off-by: Damien Riégel <damien.riegel@...abs.com>
---
drivers/greybus/cpc/Makefile | 2 +-
drivers/greybus/cpc/cpc.h | 20 ++++++++++++++
drivers/greybus/cpc/cport.c | 25 +++++++++++++++++
drivers/greybus/cpc/header.c | 17 ++++++++++++
drivers/greybus/cpc/header.h | 2 ++
drivers/greybus/cpc/host.c | 13 ++++++---
drivers/greybus/cpc/protocol.c | 49 ++++++++++++++++++++++++++++++++++
7 files changed, 123 insertions(+), 5 deletions(-)
create mode 100644 drivers/greybus/cpc/header.c
create mode 100644 drivers/greybus/cpc/protocol.c
diff --git a/drivers/greybus/cpc/Makefile b/drivers/greybus/cpc/Makefile
index 3d50f8c5473..c4b530d27a3 100644
--- a/drivers/greybus/cpc/Makefile
+++ b/drivers/greybus/cpc/Makefile
@@ -1,6 +1,6 @@
# SPDX-License-Identifier: GPL-2.0
-gb-cpc-y := cport.o host.o
+gb-cpc-y := cport.o header.o host.o protocol.o
# CPC core
obj-$(CONFIG_GREYBUS_CPC) += gb-cpc.o
diff --git a/drivers/greybus/cpc/cpc.h b/drivers/greybus/cpc/cpc.h
index 0f2d204d86d..db760cf8b32 100644
--- a/drivers/greybus/cpc/cpc.h
+++ b/drivers/greybus/cpc/cpc.h
@@ -8,17 +8,32 @@
#include <linux/device.h>
#include <linux/greybus.h>
+#include <linux/mutex.h>
#include <linux/types.h>
+struct sk_buff;
+
/**
* struct cpc_cport - CPC cport
* @id: cport ID
* @cpc_hd: pointer to the CPC host device this cport belongs to
+ * @lock: mutex to synchronize accesses to tcb and other attributes
+ * @tcb: Transmission Control Block
*/
struct cpc_cport {
u16 id;
struct cpc_host_device *cpc_hd;
+ struct mutex lock; /* Synchronize access to state variables */
+
+ /*
+ * @ack: current acknowledge number
+ * @seq: current sequence number
+ */
+ struct {
+ u8 ack;
+ u8 seq;
+ } tcb;
};
struct cpc_cport *cpc_cport_alloc(u16 cport_id, gfp_t gfp_mask);
@@ -34,8 +49,13 @@ struct cpc_skb_cb {
/* Keep track of the GB message the skb originates from */
struct gb_message *gb_message;
+
+ u8 seq;
};
#define CPC_SKB_CB(__skb) ((struct cpc_skb_cb *)&((__skb)->cb[0]))
+void cpc_protocol_prepare_header(struct sk_buff *skb, u8 ack);
+void cpc_protocol_on_data(struct cpc_cport *cport, struct sk_buff *skb);
+
#endif
diff --git a/drivers/greybus/cpc/cport.c b/drivers/greybus/cpc/cport.c
index 0fc4ff0c5bb..2ee0b129996 100644
--- a/drivers/greybus/cpc/cport.c
+++ b/drivers/greybus/cpc/cport.c
@@ -9,6 +9,16 @@
#include "cpc.h"
#include "host.h"
+/**
+ * cpc_cport_tcb_reset() - Reset cport's TCB to initial values.
+ * @cport: cport pointer
+ */
+static void cpc_cport_tcb_reset(struct cpc_cport *cport)
+{
+ cport->tcb.ack = 0;
+ cport->tcb.seq = 0;
+}
+
/**
* cpc_cport_alloc() - Allocate and initialize CPC cport.
* @cport_id: cport ID.
@@ -25,6 +35,9 @@ struct cpc_cport *cpc_cport_alloc(u16 cport_id, gfp_t gfp_mask)
return NULL;
cport->id = cport_id;
+ cpc_cport_tcb_reset(cport);
+
+ mutex_init(&cport->lock);
return cport;
}
@@ -64,10 +77,22 @@ int cpc_cport_transmit(struct cpc_cport *cport, struct sk_buff *skb)
{
struct cpc_host_device *cpc_hd = cport->cpc_hd;
struct gb_operation_msg_hdr *gb_hdr;
+ u8 ack;
/* Inject cport ID in Greybus header */
gb_hdr = (struct gb_operation_msg_hdr *)skb->data;
cpc_cport_pack(gb_hdr, cport->id);
+ mutex_lock(&cport->lock);
+
+ CPC_SKB_CB(skb)->seq = cport->tcb.seq;
+
+ cport->tcb.seq++;
+ ack = cport->tcb.ack;
+
+ mutex_unlock(&cport->lock);
+
+ cpc_protocol_prepare_header(skb, ack);
+
return cpc_hd_send_skb(cpc_hd, skb);
}
diff --git a/drivers/greybus/cpc/header.c b/drivers/greybus/cpc/header.c
new file mode 100644
index 00000000000..62946d6077e
--- /dev/null
+++ b/drivers/greybus/cpc/header.c
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2025, Silicon Laboratories, Inc.
+ */
+
+#include "header.h"
+
+/**
+ * cpc_header_get_seq() - Get the sequence number.
+ * @hdr: CPC header.
+ *
+ * Return: Sequence number.
+ */
+u8 cpc_header_get_seq(const struct cpc_header *hdr)
+{
+ return hdr->seq;
+}
diff --git a/drivers/greybus/cpc/header.h b/drivers/greybus/cpc/header.h
index 84c47f105b3..d46ad8e53fe 100644
--- a/drivers/greybus/cpc/header.h
+++ b/drivers/greybus/cpc/header.h
@@ -40,4 +40,6 @@ struct cpc_header {
#define CPC_HEADER_SIZE (sizeof(struct cpc_header))
+u8 cpc_header_get_seq(const struct cpc_header *hdr);
+
#endif
diff --git a/drivers/greybus/cpc/host.c b/drivers/greybus/cpc/host.c
index 1cce4f987e3..9173d5ab5a1 100644
--- a/drivers/greybus/cpc/host.c
+++ b/drivers/greybus/cpc/host.c
@@ -210,19 +210,24 @@ EXPORT_SYMBOL_GPL(cpc_hd_message_sent);
void cpc_hd_rcvd(struct cpc_host_device *cpc_hd, struct sk_buff *skb)
{
struct gb_operation_msg_hdr *gb_hdr;
+ struct cpc_cport *cport;
u16 cport_id;
/* Prevent an out-of-bound access if called with non-sensical parameters. */
if (skb->len < (sizeof(*gb_hdr) + CPC_HEADER_SIZE))
goto free_skb;
- skb_pull(skb, CPC_HEADER_SIZE);
-
/* Retrieve cport ID that was packed in Greybus header */
- gb_hdr = (struct gb_operation_msg_hdr *)skb->data;
+ gb_hdr = (struct gb_operation_msg_hdr *)(skb->data + CPC_HEADER_SIZE);
cport_id = cpc_cport_unpack(gb_hdr);
- greybus_data_rcvd(cpc_hd->gb_hd, cport_id, skb->data, skb->len);
+ cport = cpc_hd_get_cport(cpc_hd, cport_id);
+ if (!cport) {
+ dev_warn(cpc_hd_dev(cpc_hd), "cport %u not allocated\n", cport_id);
+ goto free_skb;
+ }
+
+ cpc_protocol_on_data(cport, skb);
free_skb:
kfree_skb(skb);
diff --git a/drivers/greybus/cpc/protocol.c b/drivers/greybus/cpc/protocol.c
new file mode 100644
index 00000000000..5684557df64
--- /dev/null
+++ b/drivers/greybus/cpc/protocol.c
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2025, Silicon Laboratories, Inc.
+ */
+
+#include <linux/skbuff.h>
+
+#include "cpc.h"
+#include "header.h"
+#include "host.h"
+
+
+void cpc_protocol_prepare_header(struct sk_buff *skb, u8 ack)
+{
+ struct cpc_header *hdr;
+
+ skb_push(skb, sizeof(*hdr));
+
+ hdr = (struct cpc_header *)skb->data;
+ hdr->ack = ack;
+ hdr->recv_wnd = 0;
+ hdr->ctrl_flags = 0;
+ hdr->seq = CPC_SKB_CB(skb)->seq;
+}
+
+void cpc_protocol_on_data(struct cpc_cport *cport, struct sk_buff *skb)
+{
+ struct cpc_header *cpc_hdr = (struct cpc_header *)skb->data;
+ u8 seq = cpc_header_get_seq(cpc_hdr);
+ bool expected_seq = false;
+
+ mutex_lock(&cport->lock);
+
+ expected_seq = seq == cport->tcb.ack;
+ if (expected_seq)
+ cport->tcb.ack++;
+ else
+ dev_warn(cpc_hd_dev(cport->cpc_hd),
+ "unexpected seq: %u, expected seq: %u\n",
+ seq, cport->tcb.ack);
+
+ mutex_unlock(&cport->lock);
+
+ if (expected_seq) {
+ skb_pull(skb, CPC_HEADER_SIZE);
+
+ greybus_data_rcvd(cport->cpc_hd->gb_hd, cport->id, skb->data, skb->len);
+ }
+}
--
2.49.0
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