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Date:   Wed, 20 May 2020 11:22:41 -0500
From:   "Sid Spry" <sid@aeam.us>
To:     linux-usb@vger.kernel.org
Subject: Unable to open(2) ep0 in ConfigFG FunctionFS Gadget
Content-Type: text/plain
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Crossreffing https://github.com/torvalds/linux/blob/2f4c53349961c8ca480193e47da4d44fdb8335a8/tools/usb/ffs-test.c it looks like all I have to do is open "ep0" in the proper directory, but I do just that and it fails on first and subsequent runs.

gadget.cc:

```
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>

#include <linux/usb/ch9.h>
#include <usbg/usbg.h>

#define VENDOR  0x1d6b
#define PRODUCT 0x0104

int usbg_setup(
        usbg_state **s,
        usbg_gadget **g,
        usbg_config **c,
        usbg_function **f_ffs0,
        usbg_function **f_ncm0
);      

int main(int argc, char *argv[]) {
        usbg_state *s;
        usbg_gadget *g;
        usbg_config *c;
        usbg_function *f_ffs0, *f_ncm0;

        if (int rc = usbg_setup(&s, &g, &c, &f_ffs0, &f_ncm0);
                rc != 0) {
                puts("gadget exists or libcomposite needs to be loaded.");
        } else {
                puts("gadget created.");
        }

        int ffs_fd = open("/sys/kernel/config/usb_gadget/g1/functions/ffs.dev0",
                O_RDONLY);
        if (int rc = fchdir(ffs_fd); rc != 0) {
                fprintf(stderr, "unable to chdir to ffs directory: %s\n",
                        strerror(errno));
        }

        int ffs_fd_ep0 = open("ep0",
                O_RDWR);
        if (ffs_fd_ep0 < 0) {
                fprintf(stderr, "unable to create ep0: %d : %s\n",
                        errno, strerror(errno));
        }

        close(ffs_fd);
}

int usbg_setup(
        usbg_state **s,
        usbg_gadget **g,
        usbg_config **c,
        usbg_function **f_ffs0,
        usbg_function **f_ncm0
) {
        struct usbg_gadget_attrs g_attrs = {
                .bcdUSB = 0x0200,
                .bDeviceClass = USB_CLASS_PER_INTERFACE,
                .bDeviceSubClass = 0x00,
                .bDeviceProtocol = 0x00,
                .bMaxPacketSize0 = 64,
                .idVendor = VENDOR,
                .idProduct = PRODUCT,
                .bcdDevice = 0x0000
        };

        struct usbg_gadget_strs g_strs = {
                .manufacturer = "Foo Inc.",
                .product = "Bar Gadget",
                .serial = "0000000000"
        };

        struct usbg_config_strs c_strs = {
                .configuration = "Default"
        };

        if (usbg_error rc = 
                        (usbg_error)usbg_init("/sys/kernel/config", s);
                rc != USBG_SUCCESS) {
                goto error_exit;
        }

        if (usbg_error rc =
                        (usbg_error)usbg_create_gadget(*s, "g1", &g_attrs, &g_strs, g);
                rc != USBG_SUCCESS) {
                goto error_exit;
        }

        if (usbg_error rc =
                        (usbg_error)usbg_create_function(*g,
                                USBG_F_NCM, "dev0", NULL, f_ncm0);
                rc != USBG_SUCCESS) {
                goto error_exit;
        }

        if (usbg_error rc =
                        (usbg_error)usbg_create_function(*g,
                                USBG_F_FFS, "dev0", NULL, f_ffs0);
                rc != USBG_SUCCESS) {
                //fprintf(stderr, "Error: %s : %s\n", usbg_error_name(rc),
                //      usbg_strerror(rc));
                goto error_exit;
        }
        
        return 0;

error_exit:
        return -2;
}
```

strace:

```
execve("./gadget", ["./gadget"], 0xbece77a0 /* 19 vars */) = 0
brk(NULL)                               = 0x1017000
uname({sysname="Linux", nodename="nanopiduo", ...}) = 0
mmap2(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb6f5e000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=35157, ...}) = 0
mmap2(NULL, 35157, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb6f55000
close(3)                                = 0
openat(AT_FDCWD, "/usr/local/lib/libusbgx.so.2", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\314I\0\0004\0\0\0"..., 512) = 512
_llseek(3, 362460, [362460], SEEK_SET)  = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1400) = 1400
_llseek(3, 50996, [50996], SEEK_SET)    = 0
read(3, "A0\0\0\0aeabi\0\1&\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 49) = 49
_llseek(3, 362460, [362460], SEEK_SET)  = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1400) = 1400
_llseek(3, 50996, [50996], SEEK_SET)    = 0
read(3, "A0\0\0\0aeabi\0\1&\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 49) = 49
_llseek(3, 362460, [362460], SEEK_SET)  = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1400) = 1400
_llseek(3, 50996, [50996], SEEK_SET)    = 0
read(3, "A0\0\0\0aeabi\0\1&\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 49) = 49
_llseek(3, 362460, [362460], SEEK_SET)  = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1400) = 1400
_llseek(3, 50996, [50996], SEEK_SET)    = 0
read(3, "A0\0\0\0aeabi\0\1&\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 49) = 49
_llseek(3, 362460, [362460], SEEK_SET)  = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1400) = 1400
_llseek(3, 50996, [50996], SEEK_SET)    = 0
read(3, "A0\0\0\0aeabi\0\1&\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 49) = 49
fstat64(3, {st_mode=S_IFREG|0755, st_size=363860, ...}) = 0
mmap2(NULL, 116508, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb6f1b000
mprotect(0xb6f27000, 61440, PROT_NONE)  = 0
mmap2(0xb6f36000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0xb000) = 0xb6f36000
close(3)                                = 0
openat(AT_FDCWD, "/usr/lib/arm-linux-gnueabihf/libconfig.so.9", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\360\"\0\0004\0\0\0"..., 512) = 512
_llseek(3, 29420, [29420], SEEK_SET)    = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 960) = 960
_llseek(3, 29096, [29096], SEEK_SET)    = 0
read(3, "A0\0\0\0aeabi\0\1&\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 49) = 49
_llseek(3, 29420, [29420], SEEK_SET)    = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 960) = 960
_llseek(3, 29096, [29096], SEEK_SET)    = 0
read(3, "A0\0\0\0aeabi\0\1&\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 49) = 49
_llseek(3, 29420, [29420], SEEK_SET)    = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 960) = 960
_llseek(3, 29096, [29096], SEEK_SET)    = 0
read(3, "A0\0\0\0aeabi\0\1&\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 49) = 49
_llseek(3, 29420, [29420], SEEK_SET)    = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 960) = 960
_llseek(3, 29096, [29096], SEEK_SET)    = 0
read(3, "A0\0\0\0aeabi\0\1&\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 49) = 49
_llseek(3, 29420, [29420], SEEK_SET)    = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 960) = 960
_llseek(3, 29096, [29096], SEEK_SET)    = 0
read(3, "A0\0\0\0aeabi\0\1&\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 49) = 49
fstat64(3, {st_mode=S_IFREG|0644, st_size=30380, ...}) = 0
mmap2(NULL, 94636, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb6f03000
mprotect(0xb6f0a000, 61440, PROT_NONE)  = 0
mmap2(0xb6f19000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x6000) = 0xb6f19000
close(3)                                = 0
openat(AT_FDCWD, "/usr/lib/arm-linux-gnueabihf/libstdc++.so.6", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 3
read(3, "\177ELF\1\1\1\3\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\270\346\6\0004\0\0\0"..., 512) = 512
_llseek(3, 1018532, [1018532], SEEK_SET) = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1240) = 1240
_llseek(3, 1017936, [1017936], SEEK_SET) = 0
read(3, "A2\0\0\0aeabi\0\1(\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 51) = 51
_llseek(3, 1018532, [1018532], SEEK_SET) = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1240) = 1240
_llseek(3, 1017936, [1017936], SEEK_SET) = 0
read(3, "A2\0\0\0aeabi\0\1(\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 51) = 51
_llseek(3, 1018532, [1018532], SEEK_SET) = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1240) = 1240
_llseek(3, 1017936, [1017936], SEEK_SET) = 0
read(3, "A2\0\0\0aeabi\0\1(\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 51) = 51
_llseek(3, 1018532, [1018532], SEEK_SET) = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1240) = 1240
_llseek(3, 1017936, [1017936], SEEK_SET) = 0
read(3, "A2\0\0\0aeabi\0\1(\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 51) = 51
_llseek(3, 1018532, [1018532], SEEK_SET) = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1240) = 1240
_llseek(3, 1017936, [1017936], SEEK_SET) = 0
read(3, "A2\0\0\0aeabi\0\1(\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 51) = 51
_llseek(3, 1018532, [1018532], SEEK_SET) = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1240) = 1240
_llseek(3, 1017936, [1017936], SEEK_SET) = 0
read(3, "A2\0\0\0aeabi\0\1(\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 51) = 51
_llseek(3, 1018532, [1018532], SEEK_SET) = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1240) = 1240
_llseek(3, 1017936, [1017936], SEEK_SET) = 0
read(3, "A2\0\0\0aeabi\0\1(\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 51) = 51
fstat64(3, {st_mode=S_IFREG|0644, st_size=1019772, ...}) = 0
mmap2(NULL, 1091308, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb6df8000
mprotect(0xb6eeb000, 61440, PROT_NONE)  = 0
mmap2(0xb6efa000, 28672, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0xf2000) = 0xb6efa000
mmap2(0xb6f01000, 5868, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb6f01000
close(3)                                = 0
openat(AT_FDCWD, "/lib/arm-linux-gnueabihf/libm.so.6", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\250r\0\0004\0\0\0"..., 512) = 512
_llseek(3, 434644, [434644], SEEK_SET)  = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1080) = 1080
_llseek(3, 434288, [434288], SEEK_SET)  = 0
read(3, "A4\0\0\0aeabi\0\1*\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 53) = 53
_llseek(3, 434644, [434644], SEEK_SET)  = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1080) = 1080
_llseek(3, 434288, [434288], SEEK_SET)  = 0
read(3, "A4\0\0\0aeabi\0\1*\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 53) = 53
_llseek(3, 434644, [434644], SEEK_SET)  = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1080) = 1080
_llseek(3, 434288, [434288], SEEK_SET)  = 0
read(3, "A4\0\0\0aeabi\0\1*\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 53) = 53
fstat64(3, {st_mode=S_IFREG|0644, st_size=435724, ...}) = 0
mmap2(NULL, 499832, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb6d7d000
mprotect(0xb6de7000, 61440, PROT_NONE)  = 0
mmap2(0xb6df6000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x69000) = 0xb6df6000
close(3)                                = 0
openat(AT_FDCWD, "/lib/arm-linux-gnueabihf/libgcc_s.so.1", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\360\321\0\0004\0\0\0"..., 512) = 512
_llseek(3, 98916, [98916], SEEK_SET)    = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1080) = 1080
_llseek(3, 98556, [98556], SEEK_SET)    = 0
read(3, "A0\0\0\0aeabi\0\1&\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 49) = 49
_llseek(3, 98916, [98916], SEEK_SET)    = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1080) = 1080
_llseek(3, 98556, [98556], SEEK_SET)    = 0
read(3, "A0\0\0\0aeabi\0\1&\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 49) = 49
_llseek(3, 98916, [98916], SEEK_SET)    = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1080) = 1080
_llseek(3, 98556, [98556], SEEK_SET)    = 0
read(3, "A0\0\0\0aeabi\0\1&\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 49) = 49
_llseek(3, 98916, [98916], SEEK_SET)    = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1080) = 1080
_llseek(3, 98556, [98556], SEEK_SET)    = 0
read(3, "A0\0\0\0aeabi\0\1&\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 49) = 49
_llseek(3, 98916, [98916], SEEK_SET)    = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1080) = 1080
_llseek(3, 98556, [98556], SEEK_SET)    = 0
read(3, "A0\0\0\0aeabi\0\1&\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 49) = 49
_llseek(3, 98916, [98916], SEEK_SET)    = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1080) = 1080
_llseek(3, 98556, [98556], SEEK_SET)    = 0
read(3, "A0\0\0\0aeabi\0\1&\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\4\22"..., 49) = 49
fstat64(3, {st_mode=S_IFREG|0644, st_size=99996, ...}) = 0
mmap2(NULL, 164148, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb6d54000
mprotect(0xb6d6c000, 61440, PROT_NONE)  = 0
mmap2(0xb6d7b000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x17000) = 0xb6d7b000
close(3)                                = 0
openat(AT_FDCWD, "/lib/arm-linux-gnueabihf/libc.so.6", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 3
read(3, "\177ELF\1\1\1\3\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\09v\1\0004\0\0\0"..., 512) = 512
_llseek(3, 949188, [949188], SEEK_SET)  = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 2840) = 2840
_llseek(3, 945756, [945756], SEEK_SET)  = 0
read(3, "A4\0\0\0aeabi\0\1*\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\3\f"..., 53) = 53
_llseek(3, 949188, [949188], SEEK_SET)  = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 2840) = 2840
_llseek(3, 945756, [945756], SEEK_SET)  = 0
read(3, "A4\0\0\0aeabi\0\1*\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\3\f"..., 53) = 53
_llseek(3, 949188, [949188], SEEK_SET)  = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 2840) = 2840
_llseek(3, 945756, [945756], SEEK_SET)  = 0
read(3, "A4\0\0\0aeabi\0\1*\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\3\f"..., 53) = 53
_llseek(3, 949188, [949188], SEEK_SET)  = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 2840) = 2840
_llseek(3, 945756, [945756], SEEK_SET)  = 0
read(3, "A4\0\0\0aeabi\0\1*\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\3\f"..., 53) = 53
_llseek(3, 949188, [949188], SEEK_SET)  = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 2840) = 2840
_llseek(3, 945756, [945756], SEEK_SET)  = 0
read(3, "A4\0\0\0aeabi\0\1*\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\3\f"..., 53) = 53
_llseek(3, 949188, [949188], SEEK_SET)  = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 2840) = 2840
_llseek(3, 945756, [945756], SEEK_SET)  = 0
read(3, "A4\0\0\0aeabi\0\1*\0\0\0\0057-A\0\6\n\7A\10\1\t\2\n\3\f"..., 53) = 53
fstat64(3, {st_mode=S_IFREG|0755, st_size=952028, ...}) = 0
mmap2(NULL, 1020732, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb6c5a000
mprotect(0xb6d3e000, 65536, PROT_NONE)  = 0
mmap2(0xb6d4e000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0xe4000) = 0xb6d4e000
mmap2(0xb6d51000, 9020, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb6d51000
close(3)                                = 0
mmap2(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb6f53000
set_tls(0xb6f534d0)                     = 0
mprotect(0xb6d4e000, 8192, PROT_READ)   = 0
mprotect(0xb6d7b000, 4096, PROT_READ)   = 0
mprotect(0xb6df6000, 4096, PROT_READ)   = 0
mprotect(0xb6efa000, 20480, PROT_READ)  = 0
mprotect(0xb6f19000, 4096, PROT_READ)   = 0
mprotect(0xb6f36000, 4096, PROT_READ)   = 0
mprotect(0x491000, 4096, PROT_READ)     = 0
mprotect(0xb6f60000, 4096, PROT_READ)   = 0
munmap(0xb6f55000, 35157)               = 0
brk(NULL)                               = 0x1017000
brk(0x1038000)                          = 0x1038000
openat(AT_FDCWD, "/sys/kernel/config/usb_gadget", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_CLOEXEC|O_DIRECTORY) = 3
fstat64(3, {st_mode=S_IFDIR|0755, st_size=0, ...}) = 0
close(3)                                = 0
openat(AT_FDCWD, "/sys/class/udc", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_CLOEXEC|O_DIRECTORY) = 3
fstat64(3, {st_mode=S_IFDIR|0755, st_size=0, ...}) = 0
getdents64(3, /* 3 entries */, 32768)   = 88
getdents64(3, /* 0 entries */, 32768)   = 0
close(3)                                = 0
openat(AT_FDCWD, "/sys/kernel/config/usb_gadget", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_CLOEXEC|O_DIRECTORY) = 3
fstat64(3, {st_mode=S_IFDIR|0755, st_size=0, ...}) = 0
getdents64(3, /* 3 entries */, 32768)   = 72
getdents64(3, /* 0 entries */, 32768)   = 0
close(3)                                = 0
openat(AT_FDCWD, "/sys/kernel/config/usb_gadget/g1/UDC", O_RDONLY) = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=4096, ...}) = 0
read(3, "\n", 4096)                     = 1
read(3, "", 4096)                       = 0
close(3)                                = 0
openat(AT_FDCWD, "/sys/kernel/config/usb_gadget/g1/functions", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_CLOEXEC|O_DIRECTORY) = 3
fstat64(3, {st_mode=S_IFDIR|0755, st_size=0, ...}) = 0
getdents64(3, /* 4 entries */, 32768)   = 112
getdents64(3, /* 0 entries */, 32768)   = 0
close(3)                                = 0
openat(AT_FDCWD, "/sys/kernel/config/usb_gadget/g1/configs", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_CLOEXEC|O_DIRECTORY) = 3
fstat64(3, {st_mode=S_IFDIR|0755, st_size=0, ...}) = 0
getdents64(3, /* 2 entries */, 32768)   = 48
getdents64(3, /* 0 entries */, 32768)   = 0
close(3)                                = 0
openat(AT_FDCWD, "/sys/kernel/config/usb_gadget/g1/os_desc", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_CLOEXEC|O_DIRECTORY) = 3
fstat64(3, {st_mode=S_IFDIR|0755, st_size=0, ...}) = 0
getdents64(3, /* 5 entries */, 32768)   = 144
getdents64(3, /* 0 entries */, 32768)   = 0
close(3)                                = 0
write(2, "usbg_create_gadget()  duplicate "..., 46usbg_create_gadget()  duplicate gadget name
 
) = 46
fstat64(1, {st_mode=S_IFCHR|0600, st_rdev=makedev(0x4, 0x40), ...}) = 0
ioctl(1, TCGETS, {B115200 opost isig icanon echo ...}) = 0
write(1, "gadget exists.\n", 15gadget exists.
)        = 15
openat(AT_FDCWD, "/sys/kernel/config/usb_gadget/g1/functions/ffs.dev0", O_RDONLY) = 3
fchdir(3)                               = 0
openat(AT_FDCWD, "ep0", O_RDWR)         = -1 ENOENT (No such file or directory)
write(2, "unable to create ep0: 2 : No suc"..., 52unable to create ep0: 2 : No such file or directory
) = 52
close(3)                                = 0
exit_group(0)                           = ?
+++ exited with 0 +++

```