USB: add read support to usb-serial/../new_id

Keep the usb-serial support for dynamic IDs in sync with the usb
support.  This enables readout of dynamic device IDs for
usb-serial drivers.  Common code is exported from the usb core
system and reused by the usb-serial bus driver.

Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 20 insertions, 4 deletions

diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index 69919b257775..f6f81c85c5cf 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -79,13 +79,12 @@ ssize_t usb_store_new_id(struct usb_dynids *dynids,
 }
 EXPORT_SYMBOL_GPL(usb_store_new_id);
 
-static ssize_t show_dynids(struct device_driver *driver, char *buf)
+ssize_t usb_show_dynids(struct usb_dynids *dynids, char *buf)
 {
         struct usb_dynid *dynid;
-        struct usb_driver *usb_drv = to_usb_driver(driver);
         size_t count = 0;
 
-        list_for_each_entry(dynid, &usb_drv->dynids.list, node)
+        list_for_each_entry(dynid, &dynids->list, node)
                 if (dynid->id.bInterfaceClass != 0)
                         count += scnprintf(&buf[count], PAGE_SIZE - count, "%04x %04x %02x\n",
                                            dynid->id.idVendor, dynid->id.idProduct,
@@ -95,6 +94,14 @@ static ssize_t show_dynids(struct device_driver *driver, char *buf)
                                            dynid->id.idVendor, dynid->id.idProduct);
         return count;
 }
+EXPORT_SYMBOL_GPL(usb_show_dynids);
+
+static ssize_t show_dynids(struct device_driver *driver, char *buf)
+{
+        struct usb_driver *usb_drv = to_usb_driver(driver);
+
+        return usb_show_dynids(&usb_drv->dynids, buf);
+}
 
 static ssize_t store_new_id(struct device_driver *driver,
                             const char *buf, size_t count)
diff --git a/drivers/usb/serial/bus.c b/drivers/usb/serial/bus.c
index ed8adb052ca7..f398d1e34474 100644
--- a/drivers/usb/serial/bus.c
+++ b/drivers/usb/serial/bus.c
@@ -124,8 +124,15 @@ static ssize_t store_new_id(struct device_driver *driver,
         return retval;
 }
 
+static ssize_t show_dynids(struct device_driver *driver, char *buf)
+{
+        struct usb_serial_driver *usb_drv = to_usb_serial_driver(driver);
+
+        return usb_show_dynids(&usb_drv->dynids, buf);
+}
+
 static struct driver_attribute drv_attrs[] = {
-        __ATTR(new_id, S_IWUSR, NULL, store_new_id),
+        __ATTR(new_id, S_IRUGO | S_IWUSR, show_dynids, store_new_id),
         __ATTR_NULL,
 };
 
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 5483cd70390b..14933451d21d 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -790,6 +790,8 @@ extern ssize_t usb_store_new_id(struct usb_dynids *dynids,
                                 struct device_driver *driver,
                                 const char *buf, size_t count);
 
+extern ssize_t usb_show_dynids(struct usb_dynids *dynids, char *buf);
+
 /**
  * struct usbdrv_wrap - wrapper for driver-model structure
  * @driver: The driver-model core driver structure.