linux-kernel - [RFC PATCH] usb: gadget: Drop unnecessary NULL checks after container

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Message-Id: <20210423150626.138188-1-linux@roeck-us.net>
Date:   Fri, 23 Apr 2021 08:06:26 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     linux-usb@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [RFC PATCH] usb: gadget: Drop unnecessary NULL checks after container_of

The parameters passed to allow_link and drop_link functions are never NULL.
That means the result of container_of() on those parameters is also
never NULL, even if the reference into the structure points to the first
element of the structure. Remove the subsequent NULL checks.

The changes in this patch were made automatically using the following
Coccinelle script.

@@
type t;
identifier v;
statement s;
@@

<+...
(
  t v = container_of(...);
|
  v = container_of(...);
)
  ...
  when != v
- if (\( !v \| v == NULL \) ) s
...+>

Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: Felipe Balbi <balbi@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
---
After the recent discussion about a patch which tried to add a check
against NULL after container_of(), I realized that there are a number
of such checks in the kernel.

Now the big question: Are patches like this acceptable, or do they count
as noise ?

Guenter

 drivers/usb/gadget/function/uvc_configfs.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/usb/gadget/function/uvc_configfs.c b/drivers/usb/gadget/function/uvc_configfs.c
index 00fb58e50a15..b9d1bcb4f4ff 100644
--- a/drivers/usb/gadget/function/uvc_configfs.c
+++ b/drivers/usb/gadget/function/uvc_configfs.c
@@ -914,8 +914,6 @@ static int uvcg_streaming_header_allow_link(struct config_item *src,
 
 	target_fmt = container_of(to_config_group(target), struct uvcg_format,
 				  group);
-	if (!target_fmt)
-		goto out;
 
 	uvcg_format_set_indices(to_config_group(target));
 
@@ -955,8 +953,6 @@ static void uvcg_streaming_header_drop_link(struct config_item *src,
 	mutex_lock(&opts->lock);
 	target_fmt = container_of(to_config_group(target), struct uvcg_format,
 				  group);
-	if (!target_fmt)
-		goto out;
 
 	list_for_each_entry_safe(format_ptr, tmp, &src_hdr->formats, entry)
 		if (format_ptr->fmt == target_fmt) {
-- 
2.17.1