[RFC PATCH 4/5] v4l2-ctl: abstract the mechanism used to print the list of controls

[Antonio Ospite <ao2@ao2.it>]

Sometimes it may be useful to list the controls using a different output
format than the current one used by --list-ctrls, for instance a new
printing format could output a string which can be later fed to
--set-ctrl.

Add an abstraction mechanism to make it possible to add new output
formats for controls.

Signed-off-by: Antonio Ospite <ao2@ao2.it>
---
 utils/v4l2-ctl/v4l2-ctl-common.cpp | 32 ++++++++++++++++++++----------
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/utils/v4l2-ctl/v4l2-ctl-common.cpp b/utils/v4l2-ctl/v4l2-ctl-common.cpp
index 5d41d720..7777b45c 100644
--- a/utils/v4l2-ctl/v4l2-ctl-common.cpp
+++ b/utils/v4l2-ctl/v4l2-ctl-common.cpp
@@ -30,6 +30,12 @@ struct ctrl_subset {
 	unsigned size[V4L2_CTRL_MAX_DIMS];
 };
 
+struct print_format {
+	void (*print_class_name)(const char *);
+	void (*print_qctrl)(int, struct v4l2_query_ext_ctrl *, struct v4l2_ext_control *, int);
+	int show_menus;
+};
+
 typedef std::map<unsigned, std::vector<struct v4l2_ext_control> > class2ctrls_map;
 
 typedef std::map<std::string, struct v4l2_query_ext_ctrl> ctrl_qmap;
@@ -408,7 +414,7 @@ static void print_class_name(const char *name)
 	printf("\n%s\n\n", name);
 }
 
-static int print_control(int fd, struct v4l2_query_ext_ctrl &qctrl, int show_menus)
+static int print_control(int fd, struct v4l2_query_ext_ctrl &qctrl, struct print_format *format)
 {
 	struct v4l2_control ctrl;
 	struct v4l2_ext_control ext_ctrl;
@@ -420,17 +426,17 @@ static int print_control(int fd, struct v4l2_query_ext_ctrl &qctrl, int show_men
 	if (qctrl.flags & V4L2_CTRL_FLAG_DISABLED)
 		return 1;
 	if (qctrl.type == V4L2_CTRL_TYPE_CTRL_CLASS) {
-		print_class_name(qctrl.name);
+		format->print_class_name(qctrl.name);
 		return 1;
 	}
 	ext_ctrl.id = qctrl.id;
 	if ((qctrl.flags & V4L2_CTRL_FLAG_WRITE_ONLY) ||
 	    qctrl.type == V4L2_CTRL_TYPE_BUTTON) {
-		print_qctrl(fd, &qctrl, &ext_ctrl, show_menus);
+		format->print_qctrl(fd, &qctrl, &ext_ctrl, format->show_menus);
 		return 1;
 	}
 	if (qctrl.type >= V4L2_CTRL_COMPOUND_TYPES) {
-		print_qctrl(fd, &qctrl, NULL, show_menus);
+		format->print_qctrl(fd, &qctrl, NULL, format->show_menus);
 		return 1;
 	}
 	ctrls.which = V4L2_CTRL_ID2WHICH(qctrl.id);
@@ -460,7 +466,7 @@ static int print_control(int fd, struct v4l2_query_ext_ctrl &qctrl, int show_men
 		}
 		ext_ctrl.value = ctrl.value;
 	}
-	print_qctrl(fd, &qctrl, &ext_ctrl, show_menus);
+	format->print_qctrl(fd, &qctrl, &ext_ctrl, format->show_menus);
 	if (qctrl.type == V4L2_CTRL_TYPE_STRING)
 		free(ext_ctrl.string);
 	return 1;
@@ -512,7 +518,7 @@ static int query_ext_ctrl_ioctl(int fd, struct v4l2_query_ext_ctrl &qctrl)
 	return rc;
 }
 
-static void list_controls(int fd, int show_menus)
+static void list_controls(int fd, struct print_format *format)
 {
 	const unsigned next_fl = V4L2_CTRL_FLAG_NEXT_CTRL | V4L2_CTRL_FLAG_NEXT_COMPOUND;
 	struct v4l2_query_ext_ctrl qctrl;
@@ -521,7 +527,7 @@ static void list_controls(int fd, int show_menus)
 	memset(&qctrl, 0, sizeof(qctrl));
 	qctrl.id = next_fl;
 	while (query_ext_ctrl_ioctl(fd, qctrl) == 0) {
-		print_control(fd, qctrl, show_menus);
+		print_control(fd, qctrl, format);
 		qctrl.id |= next_fl;
 	}
 	if (qctrl.id != next_fl)
@@ -529,11 +535,11 @@ static void list_controls(int fd, int show_menus)
 	for (id = V4L2_CID_USER_BASE; id < V4L2_CID_LASTP1; id++) {
 		qctrl.id = id;
 		if (query_ext_ctrl_ioctl(fd, qctrl) == 0)
-			print_control(fd, qctrl, show_menus);
+			print_control(fd, qctrl, format);
 	}
 	for (qctrl.id = V4L2_CID_PRIVATE_BASE;
 			query_ext_ctrl_ioctl(fd, qctrl) == 0; qctrl.id++) {
-		print_control(fd, qctrl, show_menus);
+		print_control(fd, qctrl, format);
 	}
 }
 
@@ -1097,6 +1103,12 @@ void common_get(cv4l_fd &_fd)
 void common_list(cv4l_fd &fd)
 {
 	if (options[OptListCtrls] || options[OptListCtrlsMenus]) {
-		list_controls(fd.g_fd(), options[OptListCtrlsMenus]);
+		struct print_format classic_format = {
+			.print_class_name = print_class_name,
+			.print_qctrl = print_qctrl,
+			.show_menus = options[OptListCtrlsMenus],
+		};
+
+		list_controls(fd.g_fd(), &classic_format);
 	}
 }
-- 
2.20.1