V4L/DVB (8873): gspca: Bad image offset with rev012a of spca561 and adjust exposure.

-Make raw bayer header size change from 20 to 16 affect rev072a only, my 2
 rev012a cams both have a header size of 20
-While testing this I also tested the new exposure setting (good work on
 finding the register JF), and after quite a bit of testing have found out the
 exact meaning of the register, this patch modifies setexposure to control
 the exposure over a much wider range.

Signed-off-by: Hans de Goede <j.w.r.degoede@hhs.nl>
Signed-off-by: Jean-Francois Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/gspca/spca561.c

@@ -38,9 +38,9 @@ struct sd {
 #define CONTRAST_MAX 0x3fff
 
 	__u16 exposure;			/* rev12a only */
-#define EXPOSURE_MIN 0
+#define EXPOSURE_MIN 1
 #define EXPOSURE_DEF 200
-#define EXPOSURE_MAX 762
+#define EXPOSURE_MAX (4095 - 900) /* see set_exposure */
 
 	__u8 brightness;		/* rev72a only */
 #define BRIGHTNESS_MIN 0
@@ -648,9 +648,31 @@ static void setexposure(struct gspca_dev *gspca_dev)
 {
 	struct sd *sd = (struct sd *) gspca_dev;
 	int expo;
+	int clock_divider;
 	__u8 data[2];
 
-	expo = sd->exposure + 0x20a8;	/* from test */
+	/* Register 0x8309 controls exposure for the spca561,
+	   the basic exposure setting goes from 1-2047, where 1 is completely
+	   dark and 2047 is very bright. It not only influences exposure but
+	   also the framerate (to allow for longer exposure) from 1 - 300 it
+	   only raises the exposure time then from 300 - 600 it halves the
+	   framerate to be able to further raise the exposure time and for every
+	   300 more it halves the framerate again. This allows for a maximum
+	   exposure time of circa 0.2 - 0.25 seconds (30 / (2000/3000) fps).
+	   Sometimes this is not enough, the 1-2047 uses bits 0-10, bits 11-12
+	   configure a divider for the base framerate which us used at the
+	   exposure setting of 1-300. These bits configure the base framerate
+	   according to the following formula: fps = 60 / (value + 2) */
+	if (sd->exposure < 2048) {
+		expo = sd->exposure;
+		clock_divider = 0;
+	} else {
+		/* Add 900 to make the 0 setting of the second part of the
+		   exposure equal to the 2047 setting of the first part. */
+		expo = (sd->exposure - 2048) + 900;
+		clock_divider = 3;
+	}
+	expo |= clock_divider << 11;
 	data[0] = expo;
 	data[1] = expo >> 8;
 	reg_w_buf(gspca_dev, 0x8309, data, 2);
@@ -680,23 +702,11 @@ static void setautogain(struct gspca_dev *gspca_dev)
 static void sd_start_12a(struct gspca_dev *gspca_dev)
 {
 	struct usb_device *dev = gspca_dev->dev;
-	int Clck;
+	int Clck = 0x8a; /* lower 0x8X values lead to fps > 30 */
 	__u8 Reg8307[] = { 0xaa, 0x00 };
 	int mode;
 
 	mode = gspca_dev->cam.cam_mode[(int) gspca_dev->curr_mode].priv;
-	switch (mode) {
-	case 0:
-	case 1:
-		Clck = 0x8a;
-		break;
-	case 2:
-		Clck = 0x85;
-		break;
-	default:
-		Clck = 0x83;
-		break;
-	}
 	if (mode <= 1) {
 		/* Use compression on 320x240 and above */
 		reg_w_val(dev, 0x8500, 0x10 | mode);
@@ -714,6 +724,7 @@ static void sd_start_12a(struct gspca_dev *gspca_dev)
 	setcontrast(gspca_dev);
 	setwhite(gspca_dev);
 	setautogain(gspca_dev);
+	setexposure(gspca_dev);
 }
 static void sd_start_72a(struct gspca_dev *gspca_dev)
 {
@@ -849,6 +860,8 @@ static void sd_pkt_scan(struct gspca_dev *gspca_dev,
 			__u8 *data,		/* isoc packet */
 			int len)		/* iso packet length */
 {
+	struct sd *sd = (struct sd *) gspca_dev;
+
 	switch (data[0]) {
 	case 0:		/* start of frame */
 		frame = gspca_frame_add(gspca_dev, LAST_PACKET, frame,
@@ -861,9 +874,13 @@ static void sd_pkt_scan(struct gspca_dev *gspca_dev,
 					frame, data, len);
 		} else {
 			/* raw bayer (with a header, which we skip) */
-/*fixme: is this specific to the rev012a? */
-			data += 16;
-			len -= 16;
+			if (sd->chip_revision == Rev012A) {
+				data += 20;
+				len -= 20;
+			} else {
+				data += 16;
+				len -= 16;
+			}
 			gspca_frame_add(gspca_dev, FIRST_PACKET,
 						frame, data, len);
 		}