5 files changed, 204 insertions, 2 deletions

diff --git a/Documentation/ABI/testing/configfs-usb-gadget-printer b/Documentation/ABI/testing/configfs-usb-gadget-printer
new file mode 100644
index 000000000000..6b0714e3c605
--- /dev/null
+++ b/Documentation/ABI/testing/configfs-usb-gadget-printer
@@ -0,0 +1,9 @@
+What:           /config/usb-gadget/gadget/functions/printer.name
+Date:           Apr 2015
+KernelVersion:  4.1
+Description:
+                The attributes:
+
+                pnp_string      - Data to be passed to the host in pnp string
+                q_len           - Number of requests per endpoint
+
diff --git a/Documentation/usb/gadget-testing.txt b/Documentation/usb/gadget-testing.txt
index 076ac7ba7f93..f45b2bf4b41d 100644
--- a/Documentation/usb/gadget-testing.txt
+++ b/Documentation/usb/gadget-testing.txt
@@ -19,6 +19,7 @@ provided by gadgets.
 16. UAC1 function
 17. UAC2 function
 18. UVC function
+19. PRINTER function
 
 
 1. ACM function
@@ -726,3 +727,49 @@ with these patches:
 http://www.spinics.net/lists/linux-usb/msg99220.html
 
 host: luvcview -f yuv
+
+19. PRINTER function
+====================
+
+The function is provided by usb_f_printer.ko module.
+
+Function-specific configfs interface
+------------------------------------
+
+The function name to use when creating the function directory is "printer".
+The printer function provides these attributes in its function directory:
+
+        pnp_string      - Data to be passed to the host in pnp string
+        q_len           - Number of requests per endpoint
+
+Testing the PRINTER function
+----------------------------
+
+The most basic testing:
+
+device: run the gadget
+# ls -l /devices/virtual/usb_printer_gadget/
+
+should show g_printer<number>.
+
+If udev is active, then /dev/g_printer<number> should appear automatically.
+
+host:
+
+If udev is active, then e.g. /dev/usb/lp0 should appear.
+
+host->device transmission:
+
+device:
+# cat /dev/g_printer<number>
+host:
+# cat > /dev/usb/lp0
+
+device->host transmission:
+
+# cat > /dev/g_printer<number>
+host:
+# cat /dev/usb/lp0
+
+More advanced testing can be done with the prn_example
+described in Documentation/usb/gadget-printer.txt.
diff --git a/drivers/usb/gadget/Kconfig b/drivers/usb/gadget/Kconfig
index 9d507cf98f94..3bb0e67fded2 100644
--- a/drivers/usb/gadget/Kconfig
+++ b/drivers/usb/gadget/Kconfig
@@ -437,6 +437,19 @@ config USB_CONFIGFS_F_UVC
           device. It provides a userspace API to process UVC control requests
           and stream video data to the host.
 
+config USB_CONFIGFS_F_PRINTER
+        bool "Printer function"
+        select USB_F_PRINTER
+        help
+          The Printer function 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<X> to
+          receive or send printer data. It can use ioctl calls to
+          the device file to get or set printer status.
+
+          For more information, see Documentation/usb/gadget_printer.txt
+          which includes sample code for accessing the device file.
+
 source "drivers/usb/gadget/legacy/Kconfig"
 
 endchoice
diff --git a/drivers/usb/gadget/function/f_printer.c b/drivers/usb/gadget/function/f_printer.c
index 7afe17d76f17..757fcf070013 100644
--- a/drivers/usb/gadget/function/f_printer.c
+++ b/drivers/usb/gadget/function/f_printer.c
@@ -1140,6 +1140,117 @@ static void printer_func_disable(struct usb_function *f)
         spin_unlock_irqrestore(&dev->lock, flags);
 }
 
+static inline struct f_printer_opts
+*to_f_printer_opts(struct config_item *item)
+{
+        return container_of(to_config_group(item), struct f_printer_opts,
+                            func_inst.group);
+}
+
+CONFIGFS_ATTR_STRUCT(f_printer_opts);
+CONFIGFS_ATTR_OPS(f_printer_opts);
+
+static void printer_attr_release(struct config_item *item)
+{
+        struct f_printer_opts *opts = to_f_printer_opts(item);
+
+        usb_put_function_instance(&opts->func_inst);
+}
+
+static struct configfs_item_operations printer_item_ops = {
+        .release        = printer_attr_release,
+        .show_attribute = f_printer_opts_attr_show,
+        .store_attribute = f_printer_opts_attr_store,
+};
+
+static ssize_t f_printer_opts_pnp_string_show(struct f_printer_opts *opts,
+                                              char *page)
+{
+        int result;
+
+        mutex_lock(&opts->lock);
+        result = strlcpy(page, opts->pnp_string + 2, PNP_STRING_LEN - 2);
+        mutex_unlock(&opts->lock);
+
+        return result;
+}
+
+static ssize_t f_printer_opts_pnp_string_store(struct f_printer_opts *opts,
+                                               const char *page, size_t len)
+{
+        int result, l;
+
+        mutex_lock(&opts->lock);
+        result = strlcpy(opts->pnp_string + 2, page, PNP_STRING_LEN - 2);
+        l = strlen(opts->pnp_string + 2) + 2;
+        opts->pnp_string[0] = (l >> 8) & 0xFF;
+        opts->pnp_string[1] = l & 0xFF;
+        mutex_unlock(&opts->lock);
+
+        return result;
+}
+
+static struct f_printer_opts_attribute f_printer_opts_pnp_string =
+        __CONFIGFS_ATTR(pnp_string, S_IRUGO | S_IWUSR,
+                        f_printer_opts_pnp_string_show,
+                        f_printer_opts_pnp_string_store);
+
+static ssize_t f_printer_opts_q_len_show(struct f_printer_opts *opts,
+                                         char *page)
+{
+        int result;
+
+        mutex_lock(&opts->lock);
+        result = sprintf(page, "%d\n", opts->q_len);
+        mutex_unlock(&opts->lock);
+
+        return result;
+}
+
+static ssize_t f_printer_opts_q_len_store(struct f_printer_opts *opts,
+                                          const char *page, size_t len)
+{
+        int ret;
+        u16 num;
+
+        mutex_lock(&opts->lock);
+        if (opts->refcnt) {
+                ret = -EBUSY;
+                goto end;
+        }
+
+        ret = kstrtou16(page, 0, &num);
+        if (ret)
+                goto end;
+
+        if (num > 65535) {
+                ret = -EINVAL;
+                goto end;
+        }
+
+        opts->q_len = (unsigned)num;
+        ret = len;
+end:
+        mutex_unlock(&opts->lock);
+        return ret;
+}
+
+static struct f_printer_opts_attribute f_printer_opts_q_len =
+        __CONFIGFS_ATTR(q_len, S_IRUGO | S_IWUSR, f_printer_opts_q_len_show,
+                        f_printer_opts_q_len_store);
+
+static struct configfs_attribute *printer_attrs[] = {
+        &f_printer_opts_pnp_string.attr,
+        &f_printer_opts_q_len.attr,
+        NULL,
+};
+
+static struct config_item_type printer_func_type = {
+        .ct_item_ops    = &printer_item_ops,
+        .ct_attrs       = printer_attrs,
+        .ct_owner       = THIS_MODULE,
+};
+
 static inline int gprinter_get_minor(void)
 {
         return ida_simple_get(&printer_ida, 0, 0, GFP_KERNEL);
@@ -1180,6 +1291,7 @@ static struct usb_function_instance *gprinter_alloc_inst(void)
         if (!opts)
                 return ERR_PTR(-ENOMEM);
 
+        mutex_init(&opts->lock);
         opts->func_inst.free_func_inst = gprinter_free_inst;
         ret = &opts->func_inst;
 
@@ -1201,6 +1313,8 @@ static struct usb_function_instance *gprinter_alloc_inst(void)
                 if (idr_is_empty(&printer_ida.idr))
                         gprinter_cleanup();
         }
+        config_group_init_type_name(&opts->func_inst.group, "",
+                                    &printer_func_type);
 
 unlock:
         mutex_unlock(&printer_ida_lock);
@@ -1210,8 +1324,13 @@ unlock:
 static void gprinter_free(struct usb_function *f)
 {
         struct printer_dev *dev = func_to_printer(f);
+        struct f_printer_opts *opts;
 
+        opts = container_of(f->fi, struct f_printer_opts, func_inst);
         kfree(dev);
+        mutex_lock(&opts->lock);
+        --opts->refcnt;
+        mutex_unlock(&opts->lock);
 }
 
 static void printer_func_unbind(struct usb_configuration *c,
@@ -1265,16 +1384,23 @@ static struct usb_function *gprinter_alloc(struct usb_function_instance *fi)
 
         opts = container_of(fi, struct f_printer_opts, func_inst);
 
-        if (opts->minor >= minors)
+        mutex_lock(&opts->lock);
+        if (opts->minor >= minors) {
+                mutex_unlock(&opts->lock);
                 return ERR_PTR(-ENOENT);
+        }
 
         dev = kzalloc(sizeof(*dev), GFP_KERNEL);
-        if (!dev)
+        if (!dev) {
+                mutex_unlock(&opts->lock);
                 return ERR_PTR(-ENOMEM);
+        }
 
+        ++opts->refcnt;
         dev->minor = opts->minor;
         dev->pnp_string = opts->pnp_string;
         dev->q_len = opts->q_len;
+        mutex_unlock(&opts->lock);
 
         dev->function.name = "printer";
         dev->function.bind = printer_func_bind;
diff --git a/drivers/usb/gadget/function/u_printer.h b/drivers/usb/gadget/function/u_printer.h
index b2338cacdfe4..0e2c49d4274e 100644
--- a/drivers/usb/gadget/function/u_printer.h
+++ b/drivers/usb/gadget/function/u_printer.h
@@ -25,6 +25,13 @@ struct f_printer_opts {
         int                             minor;
         char                            pnp_string[PNP_STRING_LEN];
         unsigned                        q_len;
+
+        /*
+         * Protect the data from concurrent access by read/write
+         * and create symlink/remove symlink
+         */
+        struct mutex                    lock;
+        int                             refcnt;
 };
 
 #endif /* U_PRINTER_H */