Thunderbolt config areas contain capability lists similar to those found
on pci devices. This patch introduces a tb_find_cap utility method to
search for capabilities.
Signed-off-by: Andreas Noever <andreas.noever@xxxxxxxxx>
---
drivers/thunderbolt/Makefile | 2 +-
drivers/thunderbolt/cap.c | 116 +++++++++++++++++++++++++++++++++++++++++++
drivers/thunderbolt/tb.h | 2 +
3 files changed, 119 insertions(+), 1 deletion(-)
create mode 100644 drivers/thunderbolt/cap.c
diff --git a/drivers/thunderbolt/Makefile b/drivers/thunderbolt/Makefile
index 4ac18d9..617b314 100644
--- a/drivers/thunderbolt/Makefile
+++ b/drivers/thunderbolt/Makefile
@@ -1,3 +1,3 @@
obj-${CONFIG_THUNDERBOLT} := thunderbolt.o
-thunderbolt-objs := nhi.o ctl.o tb.o switch.o
+thunderbolt-objs := nhi.o ctl.o tb.o switch.o cap.o
diff --git a/drivers/thunderbolt/cap.c b/drivers/thunderbolt/cap.c
new file mode 100644
index 0000000..a7b47e7
--- /dev/null
+++ b/drivers/thunderbolt/cap.c
@@ -0,0 +1,116 @@
+/*
+ * Thunderbolt Cactus Ridge driver - capabilities lookup
+ *
+ * Copyright (c) 2014 Andreas Noever <andreas.noever@xxxxxxxxx>
+ */
+
+#include <linux/slab.h>
+#include <linux/errno.h>
+
+#include "tb.h"
+
+
+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;
+
+static bool tb_cap_is_basic(struct tb_cap_any *cap)
+{
+ /* basic.cap is u8. This checks only the lower 8 bit of cap. */
+ return cap->basic.cap != 5;
+}
+
+static bool tb_cap_is_long(struct tb_cap_any *cap)
+{
+ return !tb_cap_is_basic(cap)
+ && cap->extended_short.next == 0
+ && cap->extended_short.length == 0;
+}
+
+static enum tb_cap tb_cap(struct tb_cap_any *cap)
+{
+ if (tb_cap_is_basic(cap))
+ return cap->basic.cap;
+ else
+ /* extended_short/long have cap at the same offset. */
+ return cap->extended_short.cap;
+}
+
+static u32 tb_cap_next(struct tb_cap_any *cap, u32 offset)
+{
+ int next;
+ if (offset == 1) {
+ /*
+ * The first pointer is part of the switch header and always
+ * a simple pointer.
+ */
+ next = cap->basic.next;
+ } else {
+ /*
+ * Somehow Intel decided to use 3 different types of capability
+ * headers. It is not like anyone could have predicted that
+ * single byte offsets are not enough...
+ */
+ if (tb_cap_is_basic(cap))
+ next = cap->basic.next;
+ else if (!tb_cap_is_long(cap))
+ next = cap->extended_short.next;
+ else
+ next = cap->extended_long.next;
+ }
+ /*
+ * "Hey, we could terminate some capability lists with a null offset
+ * and others with a pointer to the last element." - "Great idea!"
+ */
+ if (next == offset)
+ return 0;
+ return next;
+}
+
+/**
+ * tb_find_cap() - find a capability
+ *
+ * Return: Returns a positive offset if the capability was found and 0 if not.
+ * Returns an error code on failure.
+ */
+int tb_find_cap(struct tb_port *port, enum tb_cfg_space space, enum tb_cap cap)
+{
+ u32 offset = 1;
+ struct tb_cap_any header;
+ int res;
+ int retries = 10;
+ while (retries--) {
+ res = tb_port_read(port, &header, space, offset, 1);
+ if (res) {
+ /* Intel needs some help with linked lists. */
+ if (space == TB_CFG_PORT && offset == 0xa
+ && port->config.type == TB_TYPE_DP_HDMI_OUT) {
+ offset = 0x39;
+ continue;
+ }
+ return res;
+ }
+ if (offset != 1) {
+ if (tb_cap(&header) == cap)
+ return offset;
+ if (tb_cap_is_long(&header)) {
+ /* tb_cap_extended_long is 2 dwords */
+ res = tb_port_read(port, &header, space,
+ offset, 2);
+ if (res)
+ return res;
+ }
+ }
+ offset = tb_cap_next(&header, offset);
+ if (!offset)
+ return 0;
+ }
+ tb_port_WARN(port,
+ "run out of retries while looking for cap %#x in config space %d, last offset: %#x\n",
+ cap, space, offset);
+ return -EIO;
+}
diff --git a/drivers/thunderbolt/tb.h b/drivers/thunderbolt/tb.h
index 389dbb4..38e4c23 100644
--- a/drivers/thunderbolt/tb.h
+++ b/drivers/thunderbolt/tb.h
@@ -159,6 +159,8 @@ void thunderbolt_shutdown_and_free(struct tb *tb);
struct tb_switch *tb_switch_alloc(struct tb *tb, u64 route);
void tb_switch_free(struct tb_switch *sw);
+int tb_find_cap(struct tb_port *port, enum tb_cfg_space space, u32 value);
+
static inline int tb_route_length(u64 route)
{
--
2.0.0
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