media: adv7604: prevent underflow condition when reporting colorspace

Currently, adv76xx_log_status() reads some date using
io_read() which may return negative values. The current logic
doesn't check such errors, causing colorspace to be reported
on a wrong way at adv76xx_log_status(), as reported by Coverity.

If I/O error happens there, print a different message, instead
of reporting bogus messages to userspace.

Fixes: 54450f5 ("[media] adv7604: driver for the Analog Devices ADV7604 video decoder")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Reviewed-by: Hans Verkuil <hverkuil@xs4all.nl>

Author: mchehab

drivers/media/i2c/adv7604.c

@@ -2519,10 +2519,10 @@ static int adv76xx_log_status(struct v4l2_subdev *sd)
 	const struct adv76xx_chip_info *info = state->info;
 	struct v4l2_dv_timings timings;
 	struct stdi_readback stdi;
-	u8 reg_io_0x02 = io_read(sd, 0x02);
+	int ret;
+	u8 reg_io_0x02;
 	u8 edid_enabled;
 	u8 cable_det;
-
 	static const char * const csc_coeff_sel_rb[16] = {
 		"bypassed", "YPbPr601 -> RGB", "reserved", "YPbPr709 -> RGB",
 		"reserved", "RGB -> YPbPr601", "reserved", "RGB -> YPbPr709",
@@ -2621,13 +2621,21 @@ static int adv76xx_log_status(struct v4l2_subdev *sd)
 	v4l2_info(sd, "-----Color space-----\n");
 	v4l2_info(sd, "RGB quantization range ctrl: %s\n",
 			rgb_quantization_range_txt[state->rgb_quantization_range]);
-	v4l2_info(sd, "Input color space: %s\n",
-			input_color_space_txt[reg_io_0x02 >> 4]);
-	v4l2_info(sd, "Output color space: %s %s, alt-gamma %s\n",
-			(reg_io_0x02 & 0x02) ? "RGB" : "YCbCr",
-			(((reg_io_0x02 >> 2) & 0x01) ^ (reg_io_0x02 & 0x01)) ?
-				"(16-235)" : "(0-255)",
-			(reg_io_0x02 & 0x08) ? "enabled" : "disabled");
+
+	ret = io_read(sd, 0x02);
+	if (ret < 0) {
+		v4l2_info(sd, "Can't read Input/Output color space\n");
+	} else {
+		reg_io_0x02 = ret;
+
+		v4l2_info(sd, "Input color space: %s\n",
+				input_color_space_txt[reg_io_0x02 >> 4]);
+		v4l2_info(sd, "Output color space: %s %s, alt-gamma %s\n",
+				(reg_io_0x02 & 0x02) ? "RGB" : "YCbCr",
+				(((reg_io_0x02 >> 2) & 0x01) ^ (reg_io_0x02 & 0x01)) ?
+					"(16-235)" : "(0-255)",
+				(reg_io_0x02 & 0x08) ? "enabled" : "disabled");
+	}
 	v4l2_info(sd, "Color space conversion: %s\n",
 			csc_coeff_sel_rb[cp_read(sd, info->cp_csc) >> 4]);