usb: gadget: printer: add configfs support

Add support for configfs interface so that f_printer can be used as a
component of usb gadgets composed with it.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

2 files changed, 135 insertions, 2 deletions

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 */