[media] em28xx: write output frame resolution to regs 0x34+0x35 for em25xx family bridges

The Windows driver writes the output resolution to registers 0x34 (width / 16)
and 0x35 (height / 16) always.
We don't know yet what these registers are used for.

Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/usb/em28xx/em28xx-core.c

@@ -767,6 +767,13 @@ static void em28xx_capture_area_set(struct em28xx *dev, u8 hstart, u8 vstart,
 	em28xx_write_regs(dev, EM28XX_R1E_CWIDTH, &cwidth, 1);
 	em28xx_write_regs(dev, EM28XX_R1F_CHEIGHT, &cheight, 1);
 	em28xx_write_regs(dev, EM28XX_R1B_OFLOW, &overflow, 1);
+
+	/* FIXME: function/meaning of these registers ? */
+	/* FIXME: align width+height to multiples of 4 ?! */
+	if (dev->is_em25xx) {
+		em28xx_write_reg(dev, 0x34, width >> 4);
+		em28xx_write_reg(dev, 0x35, height >> 4);
+	}
 }
 
 static int em28xx_scaler_set(struct em28xx *dev, u16 h, u16 v)

drivers/media/usb/em28xx/em28xx-reg.h

@@ -48,7 +48,7 @@
 #define EM28XX_CHIPCFG2_TS_PACKETSIZE_752	0x03
 
 
-	/* GPIO/GPO registers */
+/* GPIO/GPO registers */
 #define EM2880_R04_GPO	0x04    /* em2880-em2883 only */
 #define EM28XX_R08_GPIO	0x08	/* em2820 or upper */
 
@@ -167,6 +167,13 @@
 
 #define EM28XX_R34_VBI_START_H	0x34
 #define EM28XX_R35_VBI_START_V	0x35
+/*
+ * NOTE: the EM276x (and EM25xx, EM277x/8x ?) (camera bridges) use these
+ * registers for a different unknown purpose.
+ *   => register 0x34 is set to capture width / 16
+ *   => register 0x35 is set to capture height / 16
+ */
+
 #define EM28XX_R36_VBI_WIDTH	0x36
 #define EM28XX_R37_VBI_HEIGHT	0x37