gistfile1.txt

#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>

/*
 * Print extended capabilities for an xHCI controller
 * Pass the base address as the first parameter, eg..
 * root@foo:~ # dmesg | egrep 'xhci.* mem '
 * xhci0: <XHCI (generic) USB 3.0 controller> mem 0xfd4c0000-0xfd4dffff irq 18 at device 0.0 on pci3
 *
 * root@foo:~ # ./xhcicap 0xfd4c0000
 * HCCPARAMS1 => 0x0388f283
 * xECP (0xfd4c0e20) => ID 2 (Supported protocol) Specific 0x0300
 * xECP (0xfd4c0e23) => ID 3 (Extended PM) Specific 0x4253
 */
 
#define HCCPARAMS1	0x10

struct {
	uint8_t		capid;
	char		*desc;
} caplist[] = {
	{ 1, "Legacy support" },
	{ 2, "Supported protocol" },
	{ 3, "Extended PM" },
	{ 4, "IO Virtualization" },
	{ 5, "Message interrupt" },
	{ 6, "Local memory" },
	{ 10, "Debug" },
	{ 17, "Extended message interrupt" },
	{ 0, NULL },
};

char *
getcapname(uint8_t id) {
	static char tmp[16];

	for (int i = 0; caplist[i].desc != NULL; i++) {
		if (id == caplist[i].capid)
			return(caplist[i].desc);
	}

	snprintf(tmp, sizeof(tmp) - 1, "Reserved (%d)", id);
	return(tmp);
}

uint32_t
read32(int memfd, uint32_t addr) {
	uint32_t data;

	if (pread(memfd, &data, sizeof(data), addr) == -1) {
		printf("Unable to read from 0x%08x\n", addr);
		exit(1);
	}

	return(data);
}

int
main(int argc, char **argv) {
	int memfd;
	uint32_t addr, hccparams1, capptr, tmp, ofs;
	char *end;

	if (argc != 2) {
		printf("Bad usage\n");
		exit(1);
	}

	if ((memfd = open("/dev/mem", O_RDONLY)) == -1) {
		printf("Can't open /dev/mem: %s\n", strerror(errno));
		exit(1);
	}

	addr = strtoll(argv[1], &end, 0);
	if (end == argv[1]) {
		printf("Unable to parse '%s'\n", argv[1]);
		exit(1);
	}

	hccparams1 = read32(memfd, addr + HCCPARAMS1);
	printf("HCCPARAMS1 => 0x%08x\n", hccparams1);
	capptr = (hccparams1 >> 16) * 4;

	while (1) {
		uint8_t capid;
		uint16_t capspec;

		tmp = read32(memfd, addr + capptr);
		capid = tmp & 0xff;
		ofs = (tmp & 0xff00) >> 8;
		capspec = tmp >> 16;
		if (ofs == 0)
			break;
		printf("xECP (0x%08x) => ID %d (%s) Specific 0x%04x\n", addr + capptr,
			capid, getcapname(capid), capspec);
		capptr += ofs;

	}

	close(memfd);
}