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POUSB Mass Storage linux
 

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    <p>I am new in linux device driver. I wan to write a C/C++ code to perform file transfer from raspberry pi to usb flash drive. I having difficult for the starting point, so i try on libusb for HID device sample code from signal11 and the code works fine for detecting my optical mouse with its device ID. Then i try to obtain usb flash drive vendor id somehow it give me very wired number. Finally i come out with a very silly try out by writing a bash script for cp a file to usb flash drive and activate the script in C++ and it works but i feel it is not a proper way to do it. Then i start with SCSI protocol and i very hard to understand how it works.Any guideline is appreciated.</p> <pre><code>int scsi_get_serial(int fd, void *buf, size_t buf_len) { // we shall retrieve page 0x80 as per http://en.wikipedia.org/wiki/SCSI_Inquiry_Command unsigned char inq_cmd[] = {INQUIRY, 1, 0x80, 0, buf_len, 0}; unsigned char sense[32]; struct sg_io_hdr io_hdr; int result; memset(&amp;io_hdr, 0, sizeof (io_hdr)); io_hdr.interface_id = 'S'; io_hdr.cmdp = inq_cmd; io_hdr.cmd_len = sizeof (inq_cmd); io_hdr.dxferp = buf; io_hdr.dxfer_len = buf_len; io_hdr.dxfer_direction = SG_DXFER_FROM_DEV; io_hdr.sbp = sense; io_hdr.mx_sb_len = sizeof (sense); io_hdr.timeout = 5000; result = ioctl(fd, SG_IO, &amp;io_hdr); if (result &lt; 0) return result; if ((io_hdr.info &amp; SG_INFO_OK_MASK) != SG_INFO_OK) return 1; return 0; } int main(int argc, char** argv) { //char *dev = "/dev/sda"; char *dev = "/dev/sg2"; char scsi_serial[255]; int rc; int fd; fd = open(dev, O_RDONLY | O_NONBLOCK); if (fd &lt; 0) { perror(dev); } memset(scsi_serial, 0, sizeof (scsi_serial)); rc = scsi_get_serial(fd, scsi_serial, 255); // scsi_serial[3] is the length of the serial number // scsi_serial[4] is serial number (raw, NOT null terminated) if (rc &lt; 0) { printf("FAIL, rc=%d, errno=%d\n", rc, errno); } else if (rc == 1) { printf("FAIL, rc=%d, drive doesn't report serial number\n", rc); } else { if (!scsi_serial[3]) { printf("Failed to retrieve serial for %s\n", dev); return -1; } printf("Serial Number: %.*s\n", (size_t) scsi_serial[3], (char *) &amp; scsi_serial[4]); } close(fd); return (EXIT_SUCCESS); } </code></pre> <p>I get this serial number: 00/1F</p> <p>Then i try write this in test.sh</p> <pre><code>cp /home/Desktop/stl4.pdf /media/mini_flash </code></pre> <p>and run system("./test.sh") in C++</p>
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    1. COWe need the relevant parts of your code, and the 'weird number' that you got from the device. Additionally, the output of `lspci` would really help us to determine what you have vs what was returned.
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    2. COYou're not making yourself clear. First you say you retrieve "Vendor ID", then you say you get "Serial Number" 00/1F. Those two properties are only marginally related (Products of a single vendor Serial should not recycle serial numbers, the tripled VID/PID/SN is unique)
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    3. COYa i am lost and very hard to understand the concept. i will try make myself more clear about it.Any recommended reference?
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