Hello Gil Fine,
Commit 25d905d2b819 ("thunderbolt: Allow USB3 bandwidth to be lower
than maximum supported") from Feb 12, 2024 (linux-next), leads to the
following Smatch static checker warning:
drivers/thunderbolt/tunnel.c:2113 tb_tunnel_alloc_usb3()
error: uninitialized symbol 'max_rate'.
drivers/thunderbolt/tunnel.c
2061 struct tb_tunnel *tb_tunnel_alloc_usb3(struct tb *tb, struct tb_port *up,
2062 struct tb_port *down, int max_up,
2063 int max_down)
2064 {
2065 struct tb_tunnel *tunnel;
2066 struct tb_path *path;
2067 int max_rate;
2068
2069 if (!tb_route(down->sw) && (max_up > 0 || max_down > 0)) {
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The patch adds this condition. If both of these are <= 0 then
max_rate is uninitialized.
2070 /*
2071 * For USB3 isochronous transfers, we allow bandwidth which is
2072 * not higher than 90% of maximum supported bandwidth by USB3
2073 * adapters.
2074 */
2075 max_rate = tb_usb3_max_link_rate(down, up);
2076 if (max_rate < 0)
2077 return NULL;
2078
2079 max_rate = max_rate * 90 / 100;
2080 tb_port_dbg(up, "maximum required bandwidth for USB3 tunnel %d Mb/s\n",
2081 max_rate);
2082 }
2083
2084 tunnel = tb_tunnel_alloc(tb, 2, TB_TUNNEL_USB3);
2085 if (!tunnel)
2086 return NULL;
2087
2088 tunnel->activate = tb_usb3_activate;
2089 tunnel->src_port = down;
2090 tunnel->dst_port = up;
2091 tunnel->max_up = max_up;
2092 tunnel->max_down = max_down;
2093
2094 path = tb_path_alloc(tb, down, TB_USB3_HOPID, up, TB_USB3_HOPID, 0,
2095 "USB3 Down");
2096 if (!path) {
2097 tb_tunnel_free(tunnel);
2098 return NULL;
2099 }
2100 tb_usb3_init_path(path);
2101 tunnel->paths[TB_USB3_PATH_DOWN] = path;
2102
2103 path = tb_path_alloc(tb, up, TB_USB3_HOPID, down, TB_USB3_HOPID, 0,
2104 "USB3 Up");
2105 if (!path) {
2106 tb_tunnel_free(tunnel);
2107 return NULL;
2108 }
2109 tb_usb3_init_path(path);
2110 tunnel->paths[TB_USB3_PATH_UP] = path;
2111
2112 if (!tb_route(down->sw)) {
--> 2113 tunnel->allocated_up = min(max_rate, max_up);
^^^^^^^^
2114 tunnel->allocated_down = min(max_rate, max_down);
^^^^^^^^
Uninitialized.
2115
2116 tunnel->init = tb_usb3_init;
2117 tunnel->consumed_bandwidth = tb_usb3_consumed_bandwidth;
2118 tunnel->release_unused_bandwidth =
2119 tb_usb3_release_unused_bandwidth;
2120 tunnel->reclaim_available_bandwidth =
2121 tb_usb3_reclaim_available_bandwidth;
2122 }
2123
2124 return tunnel;
2125 }
regards,
dan carpenter
