/* * Thunderbolt Cactus Ridge driver - capabilities lookup * * Copyright (c) 2014 Andreas Noever */ #include #include #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; } ch'/>

path: root/drivers/usb/isp1760

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