V4L/DVB: gspca - ov534: Fix and document setting manual exposure

Document that even if the state is a u8 value, both MSB and LSB are set
as sd->exposure represents half of the value we are going to set into
registers.

Skip setting exposure when AEC is enabled.

Signed-off-by: Antonio Ospite <ospite@studenti.unina.it>
Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/media/video/gspca/ov534.c b/drivers/media/video/gspca/ov534.c
index 2d8965003077..4fda0980be04 100644
--- a/drivers/media/video/gspca/ov534.c
+++ b/drivers/media/video/gspca/ov534.c
@@ -686,6 +686,15 @@ static void setexposure(struct gspca_dev *gspca_dev)
         struct sd *sd = (struct sd *) gspca_dev;
         u8 val;
 
+        if (sd->aec)
+                return;
+
+        /* 'val' is one byte and represents half of the exposure value we are
+         * going to set into registers, a two bytes value:
+         * 
+         *    MSB: ((u16) val << 1) >> 8   == val >> 7
+         *    LSB: ((u16) val << 1) & 0xff == val << 1
+         */
         val = sd->exposure;
         sccb_reg_write(gspca_dev, 0x08, val >> 7);
         sccb_reg_write(gspca_dev, 0x10, val << 1);