drivers/thunderbolt/cap.c

Source file repositories/reference/linux-study-clean/drivers/thunderbolt/cap.c

File Facts

System
Linux kernel
Corpus path
drivers/thunderbolt/cap.c
Extension
.c
Size
5845 bytes
Lines
257
Domain
Driver Families
Bucket
drivers/thunderbolt
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0
/*
 * Thunderbolt driver - capabilities lookup
 *
 * Copyright (c) 2014 Andreas Noever <andreas.noever@gmail.com>
 * Copyright (C) 2018, Intel Corporation
 */

#include <linux/slab.h>
#include <linux/errno.h>

#include "tb.h"

#define CAP_OFFSET_MAX		0xff
#define VSE_CAP_OFFSET_MAX	0xffff
#define TMU_ACCESS_EN		BIT(20)

static int tb_port_enable_tmu(struct tb_port *port, bool enable)
{
	struct tb_switch *sw = port->sw;
	u32 value, offset;
	int ret;

	/*
	 * Legacy devices need to have TMU access enabled before port
	 * space can be fully accessed.
	 */
	if (tb_switch_is_light_ridge(sw))
		offset = 0x26;
	else if (tb_switch_is_eagle_ridge(sw))
		offset = 0x2a;
	else
		return 0;

	ret = tb_sw_read(sw, &value, TB_CFG_SWITCH, offset, 1);
	if (ret)
		return ret;

	if (enable)
		value |= TMU_ACCESS_EN;
	else
		value &= ~TMU_ACCESS_EN;

	return tb_sw_write(sw, &value, TB_CFG_SWITCH, offset, 1);
}

static void tb_port_dummy_read(struct tb_port *port)
{
	/*
	 * When reading from next capability pointer location in port
	 * config space the read data is not cleared on LR. To avoid
	 * reading stale data on next read perform one dummy read after
	 * port capabilities are walked.
	 */
	if (tb_switch_is_light_ridge(port->sw)) {
		u32 dummy;

		tb_port_read(port, &dummy, TB_CFG_PORT, 0, 1);
	}
}

/**
 * tb_port_next_cap() - Return next capability in the linked list
 * @port: Port to find the capability for
 * @offset: Previous capability offset (%0 for start)
 *
 * Finds dword offset of the next capability in port config space
 * capability list. When passed %0 in @offset parameter, first entry
 * will be returned, if it exists.
 *
 * Return:
 * * Double word offset of the first or next capability - On success.
 * * %0 - If no next capability is found.
 * * Negative errno - Another error occurred.
 */
int tb_port_next_cap(struct tb_port *port, unsigned int offset)
{
	struct tb_cap_any header;
	int ret;

	if (!offset)
		return port->config.first_cap_offset;

	ret = tb_port_read(port, &header, TB_CFG_PORT, offset, 1);
	if (ret)
		return ret;

	return header.basic.next;
}

Annotation

Implementation Notes