As the first step for adding CPC support with Greybus, add a very
minimal module for CPC Host Devices. For now, this module only proxies
calls to the Greybus Host Device API and does nothing useful, but
further commits will use this base to add features.

Signed-off-by: Damien Riégel <damien.riegel@silabs.com>
---
 MAINTAINERS                  |  6 +++
 drivers/greybus/Kconfig      |  2 +
 drivers/greybus/Makefile     |  2 +
 drivers/greybus/cpc/Kconfig  | 10 +++++
 drivers/greybus/cpc/Makefile |  6 +++
 drivers/greybus/cpc/host.c   | 84 ++++++++++++++++++++++++++++++++++++
 drivers/greybus/cpc/host.h   | 40 +++++++++++++++++
 7 files changed, 150 insertions(+)
 create mode 100644 drivers/greybus/cpc/Kconfig
 create mode 100644 drivers/greybus/cpc/Makefile
 create mode 100644 drivers/greybus/cpc/host.c
 create mode 100644 drivers/greybus/cpc/host.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 6d1de82e6dc..56daf9ec310 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10774,6 +10774,12 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/net/ti,cc1352p7.yaml
 F:	drivers/greybus/gb-beagleplay.c
 
+GREYBUS CPC DRIVERS
+M:	Damien Riégel <damien.riegel@silabs.com>
+R:	Silicon Labs Kernel Team <linux-devel@silabs.com>
+S:	Supported
+F:	drivers/greybus/cpc/*
+
 GREYBUS SUBSYSTEM
 M:	Johan Hovold <johan@kernel.org>
 M:	Alex Elder <elder@kernel.org>
diff --git a/drivers/greybus/Kconfig b/drivers/greybus/Kconfig
index c3f056d28b0..565a0fdcb2c 100644
--- a/drivers/greybus/Kconfig
+++ b/drivers/greybus/Kconfig
@@ -30,6 +30,8 @@ config GREYBUS_BEAGLEPLAY
 	  To compile this code as a module, chose M here: the module
 	  will be called gb-beagleplay.ko
 
+source "drivers/greybus/cpc/Kconfig"
+
 config GREYBUS_ES2
 	tristate "Greybus ES3 USB host controller"
 	depends on USB
diff --git a/drivers/greybus/Makefile b/drivers/greybus/Makefile
index d986e94f889..92fe1d62691 100644
--- a/drivers/greybus/Makefile
+++ b/drivers/greybus/Makefile
@@ -21,6 +21,8 @@ ccflags-y += -I$(src)
 obj-$(CONFIG_GREYBUS_BEAGLEPLAY)	+= gb-beagleplay.o
 
 # Greybus Host controller drivers
+obj-$(CONFIG_GREYBUS_CPC)	+= cpc/
+
 gb-es2-y := es2.o
 
 obj-$(CONFIG_GREYBUS_ES2)	+= gb-es2.o
diff --git a/drivers/greybus/cpc/Kconfig b/drivers/greybus/cpc/Kconfig
new file mode 100644
index 00000000000..ab96fedd0de
--- /dev/null
+++ b/drivers/greybus/cpc/Kconfig
@@ -0,0 +1,10 @@
+# SPDX-License-Identifier: GPL-2.0
+
+config GREYBUS_CPC
+	tristate "Greybus CPC driver"
+	help
+	  Select this option if you have a Silicon Labs device that acts as a
+	  Greybus SVC.
+
+	  To compile this code as a module, chose M here: the module will be
+	  called gb-cpc.ko
diff --git a/drivers/greybus/cpc/Makefile b/drivers/greybus/cpc/Makefile
new file mode 100644
index 00000000000..490982a0ff5
--- /dev/null
+++ b/drivers/greybus/cpc/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0
+
+gb-cpc-y := host.o
+
+# CPC core
+obj-$(CONFIG_GREYBUS_CPC)	+= gb-cpc.o
diff --git a/drivers/greybus/cpc/host.c b/drivers/greybus/cpc/host.c
new file mode 100644
index 00000000000..80516517ff6
--- /dev/null
+++ b/drivers/greybus/cpc/host.c
@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2025, Silicon Laboratories, Inc.
+ */
+
+#include <linux/err.h>
+#include <linux/greybus.h>
+#include <linux/module.h>
+
+#include "host.h"
+
+static struct cpc_host_device *gb_hd_to_cpc_hd(struct gb_host_device *hd)
+{
+	return (struct cpc_host_device *)&hd->hd_priv;
+}
+
+static int cpc_gb_message_send(struct gb_host_device *gb_hd, u16 cport_id,
+			       struct gb_message *message, gfp_t gfp_mask)
+{
+	struct cpc_host_device *cpc_hd = gb_hd_to_cpc_hd(gb_hd);
+
+	return cpc_hd->driver->message_send(cpc_hd, cport_id, message, gfp_mask);
+}
+
+static void cpc_gb_message_cancel(struct gb_message *message)
+{
+	/* Not implemented */
+}
+
+static struct gb_hd_driver cpc_gb_driver = {
+	.hd_priv_size = sizeof(struct cpc_host_device),
+	.message_send = cpc_gb_message_send,
+	.message_cancel = cpc_gb_message_cancel,
+};
+
+struct cpc_host_device *cpc_hd_create(struct cpc_hd_driver *driver, struct device *parent)
+{
+	struct cpc_host_device *cpc_hd;
+	struct gb_host_device *hd;
+
+	if ((!driver->message_send) || (!driver->message_cancel)) {
+		dev_err(parent, "missing mandatory callbacks\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	hd = gb_hd_create(&cpc_gb_driver, parent, GB_CPC_MSG_SIZE_MAX, GB_CPC_NUM_CPORTS);
+	if (IS_ERR(hd))
+		return (struct cpc_host_device *)hd;
+
+	cpc_hd = gb_hd_to_cpc_hd(hd);
+	cpc_hd->gb_hd = hd;
+	cpc_hd->driver = driver;
+
+	return cpc_hd;
+}
+EXPORT_SYMBOL_GPL(cpc_hd_create);
+
+int cpc_hd_add(struct cpc_host_device *cpc_hd)
+{
+	return gb_hd_add(cpc_hd->gb_hd);
+}
+EXPORT_SYMBOL_GPL(cpc_hd_add);
+
+void cpc_hd_put(struct cpc_host_device *cpc_hd)
+{
+	return gb_hd_put(cpc_hd->gb_hd);
+}
+EXPORT_SYMBOL_GPL(cpc_hd_put);
+
+void cpc_hd_del(struct cpc_host_device *cpc_hd)
+{
+	return gb_hd_del(cpc_hd->gb_hd);
+}
+EXPORT_SYMBOL_GPL(cpc_hd_del);
+
+void cpc_hd_rcvd(struct cpc_host_device *cpc_hd, u16 cport_id, u8 *data, size_t length)
+{
+	greybus_data_rcvd(cpc_hd->gb_hd, cport_id, data, length);
+}
+EXPORT_SYMBOL_GPL(cpc_hd_rcvd);
+
+MODULE_DESCRIPTION("Greybus over CPC");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Silicon Laboratories, Inc.");
diff --git a/drivers/greybus/cpc/host.h b/drivers/greybus/cpc/host.h
new file mode 100644
index 00000000000..f55feb303f4
--- /dev/null
+++ b/drivers/greybus/cpc/host.h
@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2025, Silicon Laboratories, Inc.
+ */
+
+#ifndef __CPC_HOST_H
+#define __CPC_HOST_H
+
+#include <linux/device.h>
+#include <linux/greybus.h>
+#include <linux/types.h>
+
+#define GB_CPC_MSG_SIZE_MAX 4096
+#define GB_CPC_NUM_CPORTS 8
+
+struct cpc_host_device;
+
+struct cpc_hd_driver {
+	int (*message_send)(struct cpc_host_device *hd, u16 dest_cport_id,
+			    struct gb_message *message, gfp_t gfp_mask);
+	void (*message_cancel)(struct gb_message *message);
+};
+
+/**
+ * struct cpc_host_device - CPC host device.
+ * @gb_hd: pointer to Greybus Host Device this device belongs to.
+ * @driver: driver operations.
+ */
+struct cpc_host_device {
+	struct gb_host_device *gb_hd;
+	const struct cpc_hd_driver *driver;
+};
+
+struct cpc_host_device *cpc_hd_create(struct cpc_hd_driver *driver, struct device *parent);
+int cpc_hd_add(struct cpc_host_device *cpc_hd);
+void cpc_hd_put(struct cpc_host_device *cpc_hd);
+void cpc_hd_del(struct cpc_host_device *cpc_hd);
+void cpc_hd_rcvd(struct cpc_host_device *cpc_hd, u16 cport_id, u8 *data, size_t length);
+
+#endif
-- 
2.52.0

On Thu, Jan 15, 2026 at 10:57:54AM -0500, Damien Riégel wrote:
> As the first step for adding CPC support with Greybus, add a very
> minimal module for CPC Host Devices. For now, this module only proxies
> calls to the Greybus Host Device API and does nothing useful, but
> further commits will use this base to add features.

What is "CPC"?  I don't see a description of that anywhere here, sorry.

> +config GREYBUS_CPC
> +	tristate "Greybus CPC driver"
> +	help
> +	  Select this option if you have a Silicon Labs device that acts as a
> +	  Greybus SVC.

What type of device is that?  And again, what is "CPC"?  Specifics are
good to add here.

thanks,

greg k-h

On Fri Jan 16, 2026 at 10:11 AM EST, Greg Kroah-Hartman wrote:
> On Thu, Jan 15, 2026 at 10:57:54AM -0500, Damien Riégel wrote:
>> As the first step for adding CPC support with Greybus, add a very
>> minimal module for CPC Host Devices. For now, this module only proxies
>> calls to the Greybus Host Device API and does nothing useful, but
>> further commits will use this base to add features.
>
> What is "CPC"?  I don't see a description of that anywhere here, sorry.

Yeah, it seems I forgot to introduce the term here, and in the cover
letter as well. I'll resend a version that explains what CPC is and that
also addresses Jerome's comments.

thanks,
damien