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+
+                       Linux USB Printer Gadget Driver
+                                 06/04/2007
+
+              Copyright (C) 2007 Craig W. Nadler <craig@nadler.us>
+
+
+
+GENERAL
+=======
+
+This driver may be used if you are writing printer firmware using Linux as
+the embedded OS. This driver has nothing to do with using a printer with
+your Linux host system.
+
+You will need a USB device controller and a Linux driver for it that accepts
+a gadget / "device class" driver using the Linux USB Gadget API. After the
+USB device controller driver is loaded then load the printer gadget driver.
+This will present a printer interface to the USB Host that your USB Device
+port is connected to.
+
+This driver is structured for printer firmware that runs in user mode. The
+user mode printer firmware will read and write data from the kernel mode
+printer gadget driver using a device file. The printer returns a printer status
+byte when the USB HOST sends a device request to get the printer status.  The
+user space firmware can read or write this status byte using a device file
+/dev/g_printer . Both blocking and non-blocking read/write calls are supported.
+
+
+
+
+HOWTO USE THIS DRIVER
+=====================
+
+To load the USB device controller driver and the printer gadget driver. The
+following example uses the Netchip 2280 USB device controller driver:
+
+modprobe net2280
+modprobe g_printer
+
+
+The follow command line parameter can be used when loading the printer gadget
+(ex: modprobe g_printer idVendor=0x0525 idProduct=0xa4a8 ):
+
+idVendor - This is the Vendor ID used in the device descriptor. The default is
+        the Netchip vendor id 0x0525. YOU MUST CHANGE TO YOUR OWN VENDOR ID
+        BEFORE RELEASING A PRODUCT. If you plan to release a product and don't
+        already have a Vendor ID please see www.usb.org for details on how to
+        get one.
+
+idProduct - This is the Product ID used in the device descriptor. The default
+        is 0xa4a8, you should change this to an ID that's not used by any of
+        your other USB products if you have any. It would be a good idea to
+        start numbering your products starting with say 0x0001.
+
+bcdDevice - This is the version number of your product. It would be a good idea
+        to put your firmware version here.
+
+iManufacturer - A string containing the name of the Vendor.
+
+iProduct - A string containing the Product Name.
+
+iSerialNum - A string containing the Serial Number. This should be changed for
+        each unit of your product.
+
+iPNPstring -  The PNP ID string used for this printer. You will want to set
+        either on the command line or hard code the PNP ID string used for
+        your printer product.
+
+qlen - The number of 8k buffers to use per endpoint. The default is 10, you
+        should tune this for your product. You may also want to tune the
+        size of each buffer for your product.
+
+
+
+
+USING THE EXAMPLE CODE
+======================
+
+This example code talks to stdout, instead of a print engine.
+
+To compile the test code below:
+
+1) save it to a file called prn_example.c
+2) compile the code with the follow command:
+         gcc prn_example.c -o prn_example
+
+
+
+To read printer data from the host to stdout:
+
+        # prn_example -read_data
+
+
+To write printer data from a file (data_file) to the host:
+
+        # cat data_file | prn_example -write_data
+
+
+To get the current printer status for the gadget driver:
+
+        # prn_example -get_status
+
+        Printer status is:
+             Printer is NOT Selected
+             Paper is Out
+             Printer OK
+
+
+To set printer to Selected/On-line:
+
+        # prn_example -selected
+
+
+To set printer to Not Selected/Off-line:
+
+        # prn_example -not_selected
+
+
+To set paper status to paper out:
+
+        # prn_example -paper_out
+
+
+To set paper status to paper loaded:
+
+        # prn_example -paper_loaded
+
+
+To set error status to printer OK:
+
+        # prn_example -no_error
+
+
+To set error status to ERROR:
+
+        # prn_example -error
+
+
+
+
+EXAMPLE CODE
+============
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <linux/poll.h>
+#include <sys/ioctl.h>
+#include <linux/usb/g_printer.h>
+
+#define PRINTER_FILE                    "/dev/g_printer"
+#define BUF_SIZE                        512
+
+
+/*
+ * 'usage()' - Show program usage.
+ */
+
+static void
+usage(const char *option)               /* I - Option string or NULL */
+{
+        if (option) {
+                fprintf(stderr,"prn_example: Unknown option \"%s\"!\n",
+                                option);
+        }
+
+        fputs("\n", stderr);
+        fputs("Usage: prn_example -[options]\n", stderr);
+        fputs("Options:\n", stderr);
+        fputs("\n", stderr);
+        fputs("-get_status    Get the current printer status.\n", stderr);
+        fputs("-selected      Set the selected status to selected.\n", stderr);
+        fputs("-not_selected  Set the selected status to NOT selected.\n",
+                        stderr);
+        fputs("-error         Set the error status to error.\n", stderr);
+        fputs("-no_error      Set the error status to NO error.\n", stderr);
+        fputs("-paper_out     Set the paper status to paper out.\n", stderr);
+        fputs("-paper_loaded  Set the paper status to paper loaded.\n",
+                        stderr);
+        fputs("-read_data     Read printer data from driver.\n", stderr);
+        fputs("-write_data    Write printer sata to driver.\n", stderr);
+        fputs("-NB_read_data  (Non-Blocking) Read printer data from driver.\n",
+                        stderr);
+        fputs("\n\n", stderr);
+
+        exit(1);
+}
+
+
+static int
+read_printer_data()
+{
+        struct pollfd   fd[1];
+
+        /* Open device file for printer gadget. */
+        fd[0].fd = open(PRINTER_FILE, O_RDWR);
+        if (fd[0].fd < 0) {
+                printf("Error %d opening %s\n", fd[0].fd, PRINTER_FILE);
+                close(fd[0].fd);
+                return(-1);
+        }
+
+        fd[0].events = POLLIN | POLLRDNORM;
+
+        while (1) {
+                static char buf[BUF_SIZE];
+                int bytes_read;
+                int retval;
+
+                /* Wait for up to 1 second for data. */
+                retval = poll(fd, 1, 1000);
+
+                if (retval && (fd[0].revents & POLLRDNORM)) {
+
+                        /* Read data from printer gadget driver. */
+                        bytes_read = read(fd[0].fd, buf, BUF_SIZE);
+
+                        if (bytes_read < 0) {
+                                printf("Error %d reading from %s\n",
+                                                fd[0].fd, PRINTER_FILE);
+                                close(fd[0].fd);
+                                return(-1);
+                        } else if (bytes_read > 0) {
+                                /* Write data to standard OUTPUT (stdout). */
+                                fwrite(buf, 1, bytes_read, stdout);
+                                fflush(stdout);
+                        }
+
+                }
+
+        }
+
+        /* Close the device file. */
+        close(fd[0].fd);
+
+        return 0;
+}
+
+
+static int
+write_printer_data()
+{
+        struct pollfd   fd[1];
+
+        /* Open device file for printer gadget. */
+        fd[0].fd = open (PRINTER_FILE, O_RDWR);
+        if (fd[0].fd < 0) {
+                printf("Error %d opening %s\n", fd[0].fd, PRINTER_FILE);
+                close(fd[0].fd);
+                return(-1);
+        }
+
+        fd[0].events = POLLOUT | POLLWRNORM;
+
+        while (1) {
+                int retval;
+                static char buf[BUF_SIZE];
+                /* Read data from standard INPUT (stdin). */
+                int bytes_read = fread(buf, 1, BUF_SIZE, stdin);
+
+                if (!bytes_read) {
+                        break;
+                }
+
+                while (bytes_read) {
+
+                        /* Wait for up to 1 second to sent data. */
+                        retval = poll(fd, 1, 1000);
+
+                        /* Write data to printer gadget driver. */
+                        if (retval && (fd[0].revents & POLLWRNORM)) {
+                                retval = write(fd[0].fd, buf, bytes_read);
+                                if (retval < 0) {
+                                        printf("Error %d writing to %s\n",
+                                                        fd[0].fd,
+                                                        PRINTER_FILE);
+                                        close(fd[0].fd);
+                                        return(-1);
+                                } else {
+                                        bytes_read -= retval;
+                                }
+
+                        }
+
+                }
+
+        }
+
+        /* Wait until the data has been sent. */
+        fsync(fd[0].fd);
+
+        /* Close the device file. */
+        close(fd[0].fd);
+
+        return 0;
+}
+
+
+static int
+read_NB_printer_data()
+{
+        int             fd;
+        static char     buf[BUF_SIZE];
+        int             bytes_read;
+
+        /* Open device file for printer gadget. */
+        fd = open(PRINTER_FILE, O_RDWR|O_NONBLOCK);
+        if (fd < 0) {
+                printf("Error %d opening %s\n", fd, PRINTER_FILE);
+                close(fd);
+                return(-1);
+        }
+
+        while (1) {
+                /* Read data from printer gadget driver. */
+                bytes_read = read(fd, buf, BUF_SIZE);
+                if (bytes_read <= 0) {
+                        break;
+                }
+
+                /* Write data to standard OUTPUT (stdout). */
+                fwrite(buf, 1, bytes_read, stdout);
+                fflush(stdout);
+        }
+
+        /* Close the device file. */
+        close(fd);
+
+        return 0;
+}
+
+
+static int
+get_printer_status()
+{
+        int     retval;
+        int     fd;
+
+        /* Open device file for printer gadget. */
+        fd = open(PRINTER_FILE, O_RDWR);
+        if (fd < 0) {
+                printf("Error %d opening %s\n", fd, PRINTER_FILE);
+                close(fd);
+                return(-1);
+        }
+
+        /* Make the IOCTL call. */
+        retval = ioctl(fd, GADGET_GET_PRINTER_STATUS);
+        if (retval < 0) {
+                fprintf(stderr, "ERROR: Failed to set printer status\n");
+                return(-1);
+        }
+
+        /* Close the device file. */
+        close(fd);
+
+        return(retval);
+}
+
+
+static int
+set_printer_status(unsigned char buf, int clear_printer_status_bit)
+{
+        int     retval;
+        int     fd;
+
+        retval = get_printer_status();
+        if (retval < 0) {
+                fprintf(stderr, "ERROR: Failed to get printer status\n");
+                return(-1);
+        }
+
+        /* Open device file for printer gadget. */
+        fd = open(PRINTER_FILE, O_RDWR);
+
+        if (fd < 0) {
+                printf("Error %d opening %s\n", fd, PRINTER_FILE);
+                close(fd);
+                return(-1);
+        }
+
+        if (clear_printer_status_bit) {
+                retval &= ~buf;
+        } else {
+                retval |= buf;
+        }
+
+        /* Make the IOCTL call. */
+        if (ioctl(fd, GADGET_SET_PRINTER_STATUS, (unsigned char)retval)) {
+                fprintf(stderr, "ERROR: Failed to set printer status\n");
+                return(-1);
+        }
+
+        /* Close the device file. */
+        close(fd);
+
+        return 0;
+}
+
+
+static int
+display_printer_status()
+{
+        char    printer_status;
+
+        printer_status = get_printer_status();
+        if (printer_status < 0) {
+                fprintf(stderr, "ERROR: Failed to get printer status\n");
+                return(-1);
+        }
+
+        printf("Printer status is:\n");
+        if (printer_status & PRINTER_SELECTED) {
+                printf("     Printer is Selected\n");
+        } else {
+                printf("     Printer is NOT Selected\n");
+        }
+        if (printer_status & PRINTER_PAPER_EMPTY) {
+                printf("     Paper is Out\n");
+        } else {
+                printf("     Paper is Loaded\n");
+        }
+        if (printer_status & PRINTER_NOT_ERROR) {
+                printf("     Printer OK\n");
+        } else {
+                printf("     Printer ERROR\n");
+        }
+
+        return(0);
+}
+
+
+int
+main(int  argc, char *argv[])
+{
+        int     i;              /* Looping var */
+        int     retval = 0;
+
+        /* No Args */
+        if (argc == 1) {
+                usage(0);
+                exit(0);
+        }
+
+        for (i = 1; i < argc && !retval; i ++) {
+
+                if (argv[i][0] != '-') {
+                        continue;
+                }
+
+                if (!strcmp(argv[i], "-get_status")) {
+                        if (display_printer_status()) {
+                                retval = 1;
+                        }
+
+                } else if (!strcmp(argv[i], "-paper_loaded")) {
+                        if (set_printer_status(PRINTER_PAPER_EMPTY, 1)) {
+                                retval = 1;
+                        }
+
+                } else if (!strcmp(argv[i], "-paper_out")) {
+                        if (set_printer_status(PRINTER_PAPER_EMPTY, 0)) {
+                                retval = 1;
+                        }
+
+                } else if (!strcmp(argv[i], "-selected")) {
+                        if (set_printer_status(PRINTER_SELECTED, 0)) {
+                                retval = 1;
+                        }
+
+                } else if (!strcmp(argv[i], "-not_selected")) {
+                        if (set_printer_status(PRINTER_SELECTED, 1)) {
+                                retval = 1;
+                        }
+
+                } else if (!strcmp(argv[i], "-error")) {
+                        if (set_printer_status(PRINTER_NOT_ERROR, 1)) {
+                                retval = 1;
+                        }
+
+                } else if (!strcmp(argv[i], "-no_error")) {
+                        if (set_printer_status(PRINTER_NOT_ERROR, 0)) {
+                                retval = 1;
+                        }
+
+                } else if (!strcmp(argv[i], "-read_data")) {
+                        if (read_printer_data()) {
+                                retval = 1;
+                        }
+
+                } else if (!strcmp(argv[i], "-write_data")) {
+                        if (write_printer_data()) {
+                                retval = 1;
+                        }
+
+                } else if (!strcmp(argv[i], "-NB_read_data")) {
+                        if (read_NB_printer_data()) {
+                                retval = 1;
+                        }
+
+                } else {
+                        usage(argv[i]);
+                        retval = 1;
+                }
+        }
+
+        exit(retval);
+}