USB: add Printer Gadget Driver

G_PRINTER: Adds a USB printer gadget driver for use in printer firmware.

This adds a USB printer gadget driver for use in printer firmware.
The printer gadget channels data between the USB host and a userspace
program driving the print engine. The user space program reads and
writes the device file /dev/g_printer to receive or send printer data.
It can use ioctl calls to the device file to get or set printer status.

Signed-off-by: Craig W. Nadler <craig@nadler.us>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Documentation/usb/gadget_printer.txt

@@ -0,0 +1,510 @@
+
+                       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);
+}

drivers/usb/gadget/Kconfig

@@ -548,6 +548,20 @@ config USB_MIDI_GADGET
 	  Say "y" to link the driver statically, or "m" to build a
 	  dynamically linked module called "g_midi".
 
+config USB_G_PRINTER
+	tristate "Printer Gadget"
+	help
+	  The Printer Gadget channels data between the USB host and a
+	  userspace program driving the print engine. The user space
+	  program reads and writes the device file /dev/g_printer to
+	  receive or send printer data. It can use ioctl calls to
+	  the device file to get or set printer status.
+
+	  Say "y" to link the driver statically, or "m" to build a
+	  dynamically linked module called "g_printer".
+
+	  For more information, see Documentation/usb/gadget_printer.txt
+	  which includes sample code for accessing the device file.
 
 # put drivers that need isochronous transfer support (for audio
 # or video class gadget drivers), or specific hardware, here.

drivers/usb/gadget/Makefile

@@ -28,6 +28,8 @@ g_midi-objs			:= gmidi.o usbstring.o config.o epautoconf.o
 gadgetfs-objs			:= inode.o
 g_file_storage-objs		:= file_storage.o usbstring.o config.o \
 					epautoconf.o
+g_printer-objs			:= printer.o usbstring.o config.o \
+					epautoconf.o
 
 ifeq ($(CONFIG_USB_ETH_RNDIS),y)
 	g_ether-objs		+= rndis.o
@@ -38,5 +40,6 @@ obj-$(CONFIG_USB_ETH)		+= g_ether.o
 obj-$(CONFIG_USB_GADGETFS)	+= gadgetfs.o
 obj-$(CONFIG_USB_FILE_STORAGE)	+= g_file_storage.o
 obj-$(CONFIG_USB_G_SERIAL)	+= g_serial.o
+obj-$(CONFIG_USB_G_PRINTER)	+= g_printer.o
 obj-$(CONFIG_USB_MIDI_GADGET)	+= g_midi.o
 

include/linux/usb/Kbuild

@@ -3,4 +3,5 @@ unifdef-y += cdc.h
 unifdef-y += ch9.h
 unifdef-y += gadgetfs.h
 unifdef-y += midi.h
+unifdef-y += g_printer.h
 

include/linux/usb/g_printer.h

@@ -0,0 +1,31 @@
+/*
+ * g_printer.h -- Header file for USB Printer gadget driver
+ *
+ * Copyright (C) 2007 Craig W. Nadler
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+
+#define PRINTER_NOT_ERROR	0x08
+#define PRINTER_SELECTED	0x10
+#define PRINTER_PAPER_EMPTY	0x20
+
+/* The 'g' code is also used by gadgetfs ioctl requests.
+ * Don't add any colliding codes to either driver, and keep
+ * them in unique ranges (size 0x20 for now).
+ */
+#define GADGET_GET_PRINTER_STATUS	_IOR('g', 0x21, unsigned char)
+#define GADGET_SET_PRINTER_STATUS	_IOWR('g', 0x22, unsigned char)

include/linux/usb/gadgetfs.h

@@ -59,6 +59,11 @@ struct usb_gadgetfs_event {
 };
 
 
+/* The 'g' code is also used by printer gadget ioctl requests.
+ * Don't add any colliding codes to either driver, and keep
+ * them in unique ranges (size 0x20 for now).
+ */
+
 /* endpoint ioctls */
 
 /* IN transfers may be reported to the gadget driver as complete