From e550b99ad66cb1901bbca9433ea36cc665a8cfd6 Mon Sep 17 00:00:00 2001
From: Eugene Syromyatnikov <evgsyr@gmail.com>
Date: Sun, 19 Aug 2018 20:17:13 +0200
Subject: [PATCH] v4l2: improve control ID printing

Control ID space is hierarchical, so, higher bits provide information
about control class.

* v4l2.c (print_v4l2_cid): New function.
(print_v4l2_control): Use print_v4l2_cid for printing control ID field.
* tests/ioctl_v4l2.c: Add checks for control ID printing.
---
 tests/ioctl_v4l2.c | 30 ++++++++++++++++++++++++++++++
 v4l2.c             | 31 ++++++++++++++++++++++++++++++-
 2 files changed, 60 insertions(+), 1 deletion(-)

diff --git a/tests/ioctl_v4l2.c b/tests/ioctl_v4l2.c
index 54e9ee7c..5ddab1c6 100644
--- a/tests/ioctl_v4l2.c
+++ b/tests/ioctl_v4l2.c
@@ -690,6 +690,23 @@ main(void)
 	ioctl(-1, VIDIOC_G_CTRL, 0);
 	printf("ioctl(-1, VIDIOC_G_CTRL, NULL) = -1 EBADF (%m)\n");
 
+	static const struct v4l2_control v4l2_control_vals[] = {
+		{ .id = 0,                    .value = 3141592653U },
+		{ .id = 0x97abcd,             .value = 1234567890U },
+		{ .id = V4L2_CTRL_CLASS_USER, .value = 0 },
+		{ .id = 0x990a64,             .value = 42 },
+		{ .id = 0xa31234,             .value = 1 },
+		{ .id = 0xa40000,             .value = -1 },
+	};
+	static const char *id_strs[] = {
+		"0 /* V4L2_CID_??? */",
+		"0x97abcd /* V4L2_CID_??? */",
+		"V4L2_CTRL_CLASS_USER+0",
+		"V4L2_CID_MPEG_VIDEO_H264_CPB_SIZE",
+		"V4L2_CTRL_CLASS_DETECT+0x1234",
+		"0xa40000 /* V4L2_CID_??? */",
+	};
+
 	struct v4l2_control *const p_v4l2_control =
 		page_end - sizeof(*p_v4l2_control);
 	ioctl(-1, VIDIOC_G_CTRL, p_v4l2_control);
@@ -705,6 +722,19 @@ main(void)
 	       ", value=%d}) = -1 EBADF (%m)\n",
 	       p_v4l2_control->id, p_v4l2_control->value);
 
+	for (size_t i = 0; i < ARRAY_SIZE(id_strs); i++) {
+		struct v4l2_control v4l2_c = v4l2_control_vals[i];
+
+		ioctl(-1, VIDIOC_G_CTRL, &v4l2_c);
+		printf("ioctl(-1, VIDIOC_G_CTRL, {id=%s}) = -1 EBADF (%m)\n",
+		       id_strs[i]);
+
+		ioctl(-1, VIDIOC_S_CTRL, &v4l2_c);
+		printf("ioctl(-1, VIDIOC_S_CTRL, {id=%s, value=%d})"
+		       " = -1 EBADF (%m)\n",
+		       id_strs[i], v4l2_c.value);
+	}
+
 	/* VIDIOC_G_TUNER */
 	ioctl(-1, VIDIOC_G_TUNER, 0);
 	printf("ioctl(-1, VIDIOC_G_TUNER, NULL) = -1 EBADF (%m)\n");
diff --git a/v4l2.c b/v4l2.c
index b325cf8b..5da457c6 100644
--- a/v4l2.c
+++ b/v4l2.c
@@ -598,6 +598,34 @@ print_v4l2_input(struct tcb *const tcp, const kernel_ulong_t arg)
 #include "xlat/v4l2_control_id_bases.h"
 #include "xlat/v4l2_control_ids.h"
 
+static void
+print_v4l2_cid(const uint32_t cid)
+{
+	const char *id_name = xlookup(v4l2_control_ids, cid);
+
+	if (id_name) {
+		print_xlat_ex(cid, id_name, XLAT_STYLE_DEFAULT);
+		return;
+	}
+
+	uint64_t class_id = cid;
+	const char *class_str = xlookup_le(v4l2_control_classes, &class_id);
+
+	if (!class_str || (cid - class_id) >= 0x10000) {
+		print_xlat_ex(cid, "V4L2_CID_???", PXF_DEFAULT_STR);
+		return;
+	}
+
+	char *tmp_str;
+
+	if (asprintf(&tmp_str, "%s+%#" PRIx64,
+		     class_str, cid - class_id) < 0)
+		tmp_str = NULL;
+
+	print_xlat_ex(cid, tmp_str, XLAT_STYLE_DEFAULT);
+	free(tmp_str);
+}
+
 static int
 print_v4l2_control(struct tcb *const tcp, const kernel_ulong_t arg,
 		   const bool is_get)
@@ -608,8 +636,9 @@ print_v4l2_control(struct tcb *const tcp, const kernel_ulong_t arg,
 		tprints(", ");
 		if (umove_or_printaddr(tcp, arg, &c))
 			return RVAL_IOCTL_DECODED;
+
 		tprints("{id=");
-		printxval(v4l2_control_ids, c.id, "V4L2_CID_???");
+		print_v4l2_cid(c.id);
 		if (!is_get)
 			tprintf(", value=%d", c.value);
 		return 0;
-- 
2.40.0