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https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usbutils.git
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73 lines
1.6 KiB
C
73 lines
1.6 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Helpers for querying USB properties from sysfs
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*
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* Copied from name.c which is:
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* Copyright (C) 1999, 2000 Thomas Sailer (sailer@ife.ee.ethz.ch)
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* Copyright (C) 2013 Tom Gundersen (teg@jklm.no)
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*/
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#include <stdint.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <stdio.h>
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#include <linux/limits.h>
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#include <libusb.h>
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#include "sysfs.h"
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/*
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* The documentation of libusb_get_port_numbers() says "As per the USB 3.0
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* specs, the current maximum limit for the depth is 7."
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*/
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#define USB_MAX_DEPTH 7
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#define SYSFS_DEV_ATTR_PATH "/sys/bus/usb/devices/%s/%s"
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int get_sysfs_name(char *buf, size_t size, libusb_device *dev)
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{
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int len = 0;
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uint8_t bnum = libusb_get_bus_number(dev);
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uint8_t pnums[USB_MAX_DEPTH];
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int num_pnums;
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buf[0] = '\0';
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num_pnums = libusb_get_port_numbers(dev, pnums, sizeof(pnums));
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if (num_pnums == LIBUSB_ERROR_OVERFLOW) {
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return -1;
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} else if (num_pnums == 0) {
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/* Special-case root devices */
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return snprintf(buf, size, "usb%d", bnum);
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}
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len += snprintf(buf, size, "%d-", bnum);
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for (int i = 0; i < num_pnums; i++)
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len += snprintf(buf + len, size - len, i ? ".%d" : "%d", pnums[i]);
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return len;
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}
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int read_sysfs_prop(char *buf, size_t size, const char *sysfs_name, const char *propname)
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{
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int n, fd;
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char path[PATH_MAX];
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buf[0] = '\0';
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snprintf(path, sizeof(path), SYSFS_DEV_ATTR_PATH, sysfs_name, propname);
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fd = open(path, O_RDONLY);
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if (fd == -1)
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return 0;
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n = read(fd, buf, size);
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if (n > 0)
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buf[n-1] = '\0'; // Turn newline into null terminator
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close(fd);
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return n;
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}
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