media: media/dvb: Use kmemdup rather than duplicating its implementation

kmemdup is introduced to duplicate a region of memory in a neat way.
Rather than kmalloc/kzalloc + memcpy, which the programmer needs to
write the size twice (sometimes lead to mistakes), kmemdup improves
readability, leads to smaller code and also reduce the chances of mistakes.
Suggestion to use kmemdup rather than using kmalloc/kzalloc + memcpy.
Signed-off-by: Fuqian Huang <huangfq.daxian@gmail.com>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/dvb-core/dvbdev.c

@@ -476,7 +476,7 @@ int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev,
 		return -ENOMEM;
 	}
 
-	dvbdevfops = kzalloc(sizeof(struct file_operations), GFP_KERNEL);
+	dvbdevfops = kmemdup(template->fops, sizeof(*dvbdevfops), GFP_KERNEL);
 
 	if (!dvbdevfops){
 		kfree (dvbdev);
@@ -492,7 +492,6 @@ int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev,
 	dvbdev->fops = dvbdevfops;
 	init_waitqueue_head (&dvbdev->wait_queue);
 
-	memcpy(dvbdevfops, template->fops, sizeof(struct file_operations));
 	dvbdevfops->owner = adap->module;
 
 	list_add_tail (&dvbdev->list_head, &adap->device_list);

drivers/media/dvb-frontends/drx39xyj/drxj.c

@@ -12287,7 +12287,8 @@ struct dvb_frontend *drx39xxj_attach(struct i2c_adapter *i2c)
 	if (state == NULL)
 		goto error;
 
-	demod = kmalloc(sizeof(struct drx_demod_instance), GFP_KERNEL);
+	demod = kmemdup(&drxj_default_demod_g,
+			sizeof(struct drx_demod_instance), GFP_KERNEL);
 	if (demod == NULL)
 		goto error;
 
@@ -12311,8 +12312,6 @@ struct dvb_frontend *drx39xxj_attach(struct i2c_adapter *i2c)
 	state->demod = demod;
 
 	/* setup the demod data */
-	memcpy(demod, &drxj_default_demod_g, sizeof(struct drx_demod_instance));
-
 	demod->my_i2c_dev_addr = demod_addr;
 	demod->my_common_attr = demod_comm_attr;
 	demod->my_i2c_dev_addr->user_data = state;