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.noe...@gmail.com>
---
drivers/thunderbolt/tb.c | 103 +++++++++++++++++++++++++++++++++++++++++++++++
drivers/thunderbolt/tb.h | 2 +
2 files changed, 105 insertions(+)
diff --git a/drivers/thunderbolt/tb.c b/drivers/thunderbolt/tb.c
index d2df3be..943842b 100644
--- a/drivers/thunderbolt/tb.c
+++ b/drivers/thunderbolt/tb.c
@@ -89,6 +89,109 @@ static int tb_route_length(u64 route)
return (fls64(route) + TB_ROUTE_SHIFT - 1) / TB_ROUTE_SHIFT;
}
+
+/* thunderbolt capability lookup */
+
+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 position. */
+ 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 {
+ if (tb_cap_is_basic(cap))
+ next = cap->basic.next;
+ /* "255 byte config areas should be enough for anybody." */
+ else if (!tb_cap_is_long(cap))
+ next = cap->extended_short.next;
+ /*
+ * "Also we should have at least three types of capability
+ * headers in version 1."
+ */
+ 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 && tb_cap(&header) == cap)
+ return offset;
+ offset = tb_cap_next(&header, offset);
+ if (!offset)
+ return 0;
+ continue;
+ }
+ tb_port_WARN(port,
+ "could not find cap %#x in config space %d, last offset:
%#x\n",
+ cap,
+ space,
+ offset);
+ return -EIO;
+}
+
/* switch/port allocation & initialization */
/**
diff --git a/drivers/thunderbolt/tb.h b/drivers/thunderbolt/tb.h
index 4000f2b..e81c63a 100644
--- a/drivers/thunderbolt/tb.h
+++ b/drivers/thunderbolt/tb.h
@@ -144,4 +144,6 @@ static inline int tb_port_write(struct tb_port *port, void
*buffer,
struct tb *thunderbolt_alloc_and_start(struct tb_nhi *nhi);
void thunderbolt_shutdown_and_free(struct tb *tb);
+int tb_find_cap(struct tb_port *port, enum tb_cfg_space space, u32 value);
+
#endif
--
1.8.4.2
--
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