xhci: sideband: add initial api to register a secondary interrupter entity

Introduce XHCI sideband, which manages the USB endpoints being requested by
a client driver.  This is used for when client drivers are attempting to
offload USB endpoints to another entity for handling USB transfers.  XHCI
sec intr will allow for drivers to fetch the required information about the
transfer ring, so the user can submit transfers independently.  Expose the
required APIs for drivers to register and request for a USB endpoint and to
manage XHCI secondary interrupters.

Driver renaming, multiple ring segment page linking, proper endpoint clean
up, and allowing module compilation added by Wesley Cheng to complete
original concept code by Mathias Nyman.

Tested-by: Puma Hsu <pumahsu@google.com>
Tested-by: Daehwan Jung <dh10.jung@samsung.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Co-developed-by: Wesley Cheng <quic_wcheng@quicinc.com>
Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
Acked-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20250409194804.3773260-2-quic_wcheng@quicinc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 74 insertions, 0 deletions

diff --git a/include/linux/usb/xhci-sideband.h b/include/linux/usb/xhci-sideband.h
new file mode 100644
index 000000000000..4b382af892fa
--- /dev/null
+++ b/include/linux/usb/xhci-sideband.h
@@ -0,0 +1,74 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * xHCI host controller sideband support
+ *
+ * Copyright (c) 2023-2025, Intel Corporation.
+ *
+ * Author: Mathias Nyman <mathias.nyman@linux.intel.com>
+ */
+#ifndef __LINUX_XHCI_SIDEBAND_H
+#define __LINUX_XHCI_SIDEBAND_H
+
+#include <linux/scatterlist.h>
+#include <linux/usb.h>
+
+#define	EP_CTX_PER_DEV		31	/* FIXME defined twice, from xhci.h */
+
+struct xhci_sideband;
+
+enum xhci_sideband_type {
+	XHCI_SIDEBAND_AUDIO,
+	XHCI_SIDEBAND_VENDOR,
+};
+
+/**
+ * struct xhci_sideband - representation of a sideband accessed usb device.
+ * @xhci: The xhci host controller the usb device is connected to
+ * @vdev: the usb device accessed via sideband
+ * @eps: array of endpoints controlled via sideband
+ * @ir: event handling and buffer for sideband accessed device
+ * @type: xHCI sideband type
+ * @mutex: mutex for sideband operations
+ * @intf: USB sideband client interface
+ *
+ * FIXME usb device accessed via sideband Keeping track of sideband accessed usb devices.
+ */
+struct xhci_sideband {
+	struct xhci_hcd                 *xhci;
+	struct xhci_virt_device         *vdev;
+	struct xhci_virt_ep             *eps[EP_CTX_PER_DEV];
+	struct xhci_interrupter         *ir;
+	enum xhci_sideband_type		type;
+
+	/* Synchronizing xHCI sideband operations with client drivers operations */
+	struct mutex			mutex;
+
+	struct usb_interface		*intf;
+};
+
+struct xhci_sideband *
+xhci_sideband_register(struct usb_interface *intf, enum xhci_sideband_type type);
+void
+xhci_sideband_unregister(struct xhci_sideband *sb);
+int
+xhci_sideband_add_endpoint(struct xhci_sideband *sb,
+			   struct usb_host_endpoint *host_ep);
+int
+xhci_sideband_remove_endpoint(struct xhci_sideband *sb,
+			      struct usb_host_endpoint *host_ep);
+int
+xhci_sideband_stop_endpoint(struct xhci_sideband *sb,
+			    struct usb_host_endpoint *host_ep);
+struct sg_table *
+xhci_sideband_get_endpoint_buffer(struct xhci_sideband *sb,
+				  struct usb_host_endpoint *host_ep);
+struct sg_table *
+xhci_sideband_get_event_buffer(struct xhci_sideband *sb);
+int
+xhci_sideband_create_interrupter(struct xhci_sideband *sb, int num_seg,
+				 bool ip_autoclear, u32 imod_interval);
+void
+xhci_sideband_remove_interrupter(struct xhci_sideband *sb);
+int
+xhci_sideband_interrupter_id(struct xhci_sideband *sb);
+#endif /* __LINUX_XHCI_SIDEBAND_H */