Commit 3c9c3902 authored Jul 26, 2020 by Julia Lawall Committed by Mauro Carvalho Chehab Sep 01, 2020

tm6000: drop unnecessary list_empty

list_for_each_entry is able to handle an empty list.
The only effect of avoiding the loop is not initializing the
index variable.
Drop list_empty tests in cases where these variables are not
used.

Note that list_for_each_entry is defined in terms of list_first_entry,
which indicates that it should not be used on an empty list.  But in
list_for_each_entry, the element obtained by list_first_entry is not
really accessed, only the address of its list_head field is compared
to the address of the list head, so the list_first_entry is safe.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/

)

<smpl>
@@
expression x,e;
iterator name list_for_each_entry;
statement S;
identifier i;
@@

-if (!(list_empty(x))) {
   list_for_each_entry(i,x,...) S
- }
 ... when != i
? i = e
</smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

parent a357a784

drivers/media/usb/tm6000/tm6000-core.c

+9 −15

Original line number	Diff line number	Diff line
		@@ -853,12 +853,10 @@ int tm6000_call_fillbuf(struct tm6000_core *dev, enum tm6000_ops_type type,

		/* FIXME: tm6000_extension_devlist_lock should be a spinlock */

		if (!list_empty(&tm6000_extension_devlist)) {
		list_for_each_entry(ops, &tm6000_extension_devlist, next) {
		if (ops->fillbuf && ops->type == type)
		ops->fillbuf(dev, buf, size);
		}
		}

		return 0;
		}
		@@ -898,12 +896,10 @@ void tm6000_init_extension(struct tm6000_core *dev)
		struct tm6000_ops *ops = NULL;

		mutex_lock(&tm6000_devlist_mutex);
		if (!list_empty(&tm6000_extension_devlist)) {
		list_for_each_entry(ops, &tm6000_extension_devlist, next) {
		if (ops->init)
		ops->init(dev);
		}
		}
		mutex_unlock(&tm6000_devlist_mutex);
		}

		@@ -912,11 +908,9 @@ void tm6000_close_extension(struct tm6000_core *dev)
		struct tm6000_ops *ops = NULL;

		mutex_lock(&tm6000_devlist_mutex);
		if (!list_empty(&tm6000_extension_devlist)) {
		list_for_each_entry(ops, &tm6000_extension_devlist, next) {
		if (ops->fini)
		ops->fini(dev);
		}
		}
		mutex_unlock(&tm6000_devlist_mutex);
		}