usb: uvc: make uvc_format_desc table const

Since the uvc_fmts array can not be modified we declare it const and
change every user of the uvc_format_by_guid function aswell.
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>
Tested-by: Daniel Scally <dan.scally@ideasonboard.com>
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Link: https://lore.kernel.org/r/20230126231456.3402323-5-m.grzeschik@pengutronix.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/media/common/uvc.c

@@ -11,7 +11,7 @@
  * Video formats
  */
 
-static struct uvc_format_desc uvc_fmts[] = {
+static const struct uvc_format_desc uvc_fmts[] = {
 	{
 		.name		= "YUV 4:2:2 (YUYV)",
 		.guid		= UVC_GUID_FORMAT_YUY2,
@@ -204,7 +204,7 @@ static struct uvc_format_desc uvc_fmts[] = {
 	},
 };
 
-struct uvc_format_desc *uvc_format_by_guid(const u8 guid[16])
+const struct uvc_format_desc *uvc_format_by_guid(const u8 guid[16])
 {
 	unsigned int len = ARRAY_SIZE(uvc_fmts);
 	unsigned int i;

drivers/media/usb/uvc/uvc_driver.c

@@ -225,7 +225,7 @@ static int uvc_parse_format(struct uvc_device *dev,
 {
 	struct usb_interface *intf = streaming->intf;
 	struct usb_host_interface *alts = intf->cur_altsetting;
-	struct uvc_format_desc *fmtdesc;
+	const struct uvc_format_desc *fmtdesc;
 	struct uvc_frame *frame;
 	const unsigned char *start = buffer;
 	unsigned int width_multiplier = 1;

drivers/usb/gadget/function/uvc_v4l2.c

@@ -27,10 +27,10 @@
 #include "uvc_v4l2.h"
 #include "uvc_configfs.h"
 
-static struct uvc_format_desc *to_uvc_format(struct uvcg_format *uformat)
+static const struct uvc_format_desc *to_uvc_format(struct uvcg_format *uformat)
 {
 	char guid[16] = UVC_GUID_FORMAT_MJPEG;
-	struct uvc_format_desc *format;
+	const struct uvc_format_desc *format;
 	struct uvcg_uncompressed *unc;
 
 	if (uformat->type == UVCG_UNCOMPRESSED) {
@@ -119,7 +119,7 @@ static struct uvcg_format *find_format_by_pix(struct uvc_device *uvc,
 	struct uvcg_format *uformat = NULL;
 
 	list_for_each_entry(format, &uvc->header->formats, entry) {
-		struct uvc_format_desc *fmtdesc = to_uvc_format(format->fmt);
+		const struct uvc_format_desc *fmtdesc = to_uvc_format(format->fmt);
 
 		if (fmtdesc->fcc == pixelformat) {
 			uformat = format->fmt;
@@ -364,7 +364,7 @@ uvc_v4l2_enum_format(struct file *file, void *fh, struct v4l2_fmtdesc *f)
 {
 	struct video_device *vdev = video_devdata(file);
 	struct uvc_device *uvc = video_get_drvdata(vdev);
-	struct uvc_format_desc *fmtdesc;
+	const struct uvc_format_desc *fmtdesc;
 	struct uvcg_format *uformat;
 
 	if (f->index >= uvc->header->num_fmt)

include/linux/usb/uvc.h

@@ -154,6 +154,6 @@ struct uvc_format_desc {
 	u32 fcc;
 };
 
-struct uvc_format_desc *uvc_format_by_guid(const u8 guid[16]);
+const struct uvc_format_desc *uvc_format_by_guid(const u8 guid[16]);
 
 #endif /* __LINUX_V4L2_UVC_H */