v4.19.13 snapshot.
diff --git a/drivers/thunderbolt/cap.c b/drivers/thunderbolt/cap.c
new file mode 100644
index 0000000..c2277b8
--- /dev/null
+++ b/drivers/thunderbolt/cap.c
@@ -0,0 +1,130 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Thunderbolt Cactus Ridge driver - capabilities lookup
+ *
+ * Copyright (c) 2014 Andreas Noever <andreas.noever@gmail.com>
+ */
+
+#include <linux/slab.h>
+#include <linux/errno.h>
+
+#include "tb.h"
+
+#define CAP_OFFSET_MAX 0xff
+#define VSE_CAP_OFFSET_MAX 0xffff
+
+struct tb_cap_any {
+ union {
+ struct tb_cap_basic basic;
+ struct tb_cap_extended_short extended_short;
+ struct tb_cap_extended_long extended_long;
+ };
+} __packed;
+
+/**
+ * tb_port_find_cap() - Find port capability
+ * @port: Port to find the capability for
+ * @cap: Capability to look
+ *
+ * Returns offset to start of capability or %-ENOENT if no such
+ * capability was found. Negative errno is returned if there was an
+ * error.
+ */
+int tb_port_find_cap(struct tb_port *port, enum tb_port_cap cap)
+{
+ u32 offset;
+
+ /*
+ * DP out adapters claim to implement TMU capability but in
+ * reality they do not so we hard code the adapter specific
+ * capability offset here.
+ */
+ if (port->config.type == TB_TYPE_DP_HDMI_OUT)
+ offset = 0x39;
+ else
+ offset = 0x1;
+
+ do {
+ struct tb_cap_any header;
+ int ret;
+
+ ret = tb_port_read(port, &header, TB_CFG_PORT, offset, 1);
+ if (ret)
+ return ret;
+
+ if (header.basic.cap == cap)
+ return offset;
+
+ offset = header.basic.next;
+ } while (offset);
+
+ return -ENOENT;
+}
+
+static int tb_switch_find_cap(struct tb_switch *sw, enum tb_switch_cap cap)
+{
+ int offset = sw->config.first_cap_offset;
+
+ while (offset > 0 && offset < CAP_OFFSET_MAX) {
+ struct tb_cap_any header;
+ int ret;
+
+ ret = tb_sw_read(sw, &header, TB_CFG_SWITCH, offset, 1);
+ if (ret)
+ return ret;
+
+ if (header.basic.cap == cap)
+ return offset;
+
+ offset = header.basic.next;
+ }
+
+ return -ENOENT;
+}
+
+/**
+ * tb_switch_find_vse_cap() - Find switch vendor specific capability
+ * @sw: Switch to find the capability for
+ * @vsec: Vendor specific capability to look
+ *
+ * Functions enumerates vendor specific capabilities (VSEC) of a switch
+ * and returns offset when capability matching @vsec is found. If no
+ * such capability is found returns %-ENOENT. In case of error returns
+ * negative errno.
+ */
+int tb_switch_find_vse_cap(struct tb_switch *sw, enum tb_switch_vse_cap vsec)
+{
+ struct tb_cap_any header;
+ int offset;
+
+ offset = tb_switch_find_cap(sw, TB_SWITCH_CAP_VSE);
+ if (offset < 0)
+ return offset;
+
+ while (offset > 0 && offset < VSE_CAP_OFFSET_MAX) {
+ int ret;
+
+ ret = tb_sw_read(sw, &header, TB_CFG_SWITCH, offset, 2);
+ if (ret)
+ return ret;
+
+ /*
+ * Extended vendor specific capabilities come in two
+ * flavors: short and long. The latter is used when
+ * offset is over 0xff.
+ */
+ if (offset >= CAP_OFFSET_MAX) {
+ if (header.extended_long.vsec_id == vsec)
+ return offset;
+ offset = header.extended_long.next;
+ } else {
+ if (header.extended_short.vsec_id == vsec)
+ return offset;
+ if (!header.extended_short.length)
+ return -ENOENT;
+ offset = header.extended_short.next;
+ }
+ }
+
+ return -ENOENT;
+}