Input: add generic support for sparse keymaps

More and more devices choose to reimplement support for sparse keymaps
first introduced by wistron driver. Move it into a library module so it
can be easily used by interested parties.

Reviewed-by: Anisse Astier <anisse@astier.eu>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

1 files changed, 10 insertions, 4 deletions

diff --git a/drivers/input/input-polldev.c b/drivers/input/input-polldev.c
index 6a2eb399b988..aa6713b4a988 100644
--- a/drivers/input/input-polldev.c
+++ b/drivers/input/input-polldev.c
@@ -212,7 +212,7 @@ EXPORT_SYMBOL(input_allocate_polled_device);
  * @dev: device to free
  *
  * The function frees memory allocated for polling device and drops
- * reference to the associated input device (if present).
+ * reference to the associated input device.
  */
 void input_free_polled_device(struct input_polled_dev *dev)
 {
@@ -258,6 +258,15 @@ int input_register_polled_device(struct input_polled_dev *dev)
                 return error;
         }
 
+        /*
+         * Take extra reference to the underlying input device so
+         * that it survives call to input_unregister_polled_device()
+         * and is deleted only after input_free_polled_device()
+         * has been invoked. This is needed to ease task of freeing
+         * sparse keymaps.
+         */
+        input_get_device(input);
+
         return 0;
 }
 EXPORT_SYMBOL(input_register_polled_device);
@@ -269,8 +278,6 @@ EXPORT_SYMBOL(input_register_polled_device);
  * The function unregisters previously registered polled input
  * device from input layer. Polling is stopped and device is
  * ready to be freed with call to input_free_polled_device().
- * Callers should not attempt to access dev->input pointer
- * after calling this function.
  */
 void input_unregister_polled_device(struct input_polled_dev *dev)
 {
@@ -278,7 +285,6 @@ void input_unregister_polled_device(struct input_polled_dev *dev)
                            &input_polldev_attribute_group);
 
         input_unregister_device(dev->input);
-        dev->input = NULL;
 }
 EXPORT_SYMBOL(input_unregister_polled_device);