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media: cx231xx: drop unnecessary list_empty

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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>
This commit is contained in:
Julia Lawall 2020-07-26 12:58:28 +02:00 committed by Mauro Carvalho Chehab
parent 1771e9fb67
commit a50732124b
1 changed files with 6 additions and 10 deletions
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16
drivers/media/usb/cx231xx/cx231xx-core.c
View File

@ -115,11 +115,9 @@ void cx231xx_init_extension(struct cx231xx *dev)
struct cx231xx_ops *ops = NULL;
mutex_lock(&cx231xx_devlist_mutex);
if (!list_empty(&cx231xx_extension_devlist)) {
list_for_each_entry(ops, &cx231xx_extension_devlist, next) {
if (ops->init)
ops->init(dev);
}
list_for_each_entry(ops, &cx231xx_extension_devlist, next) {
if (ops->init)
ops->init(dev);
}
mutex_unlock(&cx231xx_devlist_mutex);
}
@ -129,11 +127,9 @@ void cx231xx_close_extension(struct cx231xx *dev)
struct cx231xx_ops *ops = NULL;
mutex_lock(&cx231xx_devlist_mutex);
if (!list_empty(&cx231xx_extension_devlist)) {
list_for_each_entry(ops, &cx231xx_extension_devlist, next) {
if (ops->fini)
ops->fini(dev);
}
list_for_each_entry(ops, &cx231xx_extension_devlist, next) {
if (ops->fini)
ops->fini(dev);
}
mutex_unlock(&cx231xx_devlist_mutex);
}