linux-kernel - [PATCH] media: usbtv: constify static structs

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Date:   Sat,  6 Feb 2021 22:21:39 +0100
From:   Rikard Falkeborn <rikard.falkeborn@...il.com>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Lubomir Rintel <lkundrak@...sk>,
        Johan Hovold <johan@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rikard Falkeborn <rikard.falkeborn@...il.com>
Subject: [PATCH] media: usbtv: constify static structs

Constify two static structs which are never modified to allow the
compiler to put them in read-only memory.

The only usage of norm_params is only read from it in
usbtv_configure_for_norm(). Making it const shrinks the resulting
ko-file with 300 bytes (tested with gcc 10).

The only usage of usbtv_ioctl_ops is to put its address to the ioctl_ops
field in the video_device struct. Making it const moves ~1kb to
read-only memory.

Signed-off-by: Rikard Falkeborn <rikard.falkeborn@...il.com>
---
 drivers/media/usb/usbtv/usbtv-video.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/media/usb/usbtv/usbtv-video.c b/drivers/media/usb/usbtv/usbtv-video.c
index 3b4a2e769230..a714ad77ca8e 100644
--- a/drivers/media/usb/usbtv/usbtv-video.c
+++ b/drivers/media/usb/usbtv/usbtv-video.c
@@ -47,7 +47,7 @@
 
 #include "usbtv.h"
 
-static struct usbtv_norm_params norm_params[] = {
+static const struct usbtv_norm_params norm_params[] = {
 	{
 		.norm = V4L2_STD_525_60,
 		.cap_width = 720,
@@ -63,7 +63,7 @@ static struct usbtv_norm_params norm_params[] = {
 static int usbtv_configure_for_norm(struct usbtv *usbtv, v4l2_std_id norm)
 {
 	int i, ret = 0;
-	struct usbtv_norm_params *params = NULL;
+	const struct usbtv_norm_params *params = NULL;
 
 	for (i = 0; i < ARRAY_SIZE(norm_params); i++) {
 		if (norm_params[i].norm & norm) {
@@ -685,7 +685,7 @@ static int usbtv_s_input(struct file *file, void *priv, unsigned int i)
 	return usbtv_select_input(usbtv, i);
 }
 
-static struct v4l2_ioctl_ops usbtv_ioctl_ops = {
+static const struct v4l2_ioctl_ops usbtv_ioctl_ops = {
 	.vidioc_querycap = usbtv_querycap,
 	.vidioc_enum_input = usbtv_enum_input,
 	.vidioc_enum_fmt_vid_cap = usbtv_enum_fmt_vid_cap,
-- 
2.30.0