V4L/DVB (8357): gspca: Perfect exposure for sn9c10x, sensor ov6650.

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@infradead.org>

1 files changed, 43 insertions, 11 deletions

diff --git a/drivers/media/video/gspca/sonixb.c b/drivers/media/video/gspca/sonixb.c
index c0ce21fe85f7..7303df0dc16b 100644
--- a/drivers/media/video/gspca/sonixb.c
+++ b/drivers/media/video/gspca/sonixb.c
@@ -121,8 +121,8 @@ static struct ctrl sd_ctrls[] = {
                         .id = V4L2_CID_EXPOSURE,
                         .type = V4L2_CTRL_TYPE_INTEGER,
                         .name = "Exposure",
-#define EXPOSURE_DEF 0
-#define EXPOSURE_KNEE 176 /* 10 fps */
+#define EXPOSURE_DEF  16 /*  32 ms / 30 fps */
+#define EXPOSURE_KNEE 50 /* 100 ms / 10 fps */
                         .minimum = 0,
                         .maximum = 255,
                         .step = 1,
@@ -611,8 +611,6 @@ static void setgain(struct gspca_dev *gspca_dev)
 static void setexposure(struct gspca_dev *gspca_dev)
 {
         struct sd *sd = (struct sd *) gspca_dev;
-        /* translate 0 - 255 to a number of fps in a 30 - 1 scale */
-        int fps = 30 - sd->exposure * 29 / 255;
 
         switch (sd->sensor) {
         case SENSOR_TAS5110: {
@@ -621,19 +619,53 @@ static void setexposure(struct gspca_dev *gspca_dev)
                 /* register 19's high nibble contains the sn9c10x clock divider
                    The high nibble configures the no fps according to the
                    formula: 60 / high_nibble. With a maximum of 30 fps */
-                reg = 60 / fps;
-                if (reg > 15)
+                reg = 120 * sd->exposure / 1000;
+                if (reg < 2)
+                        reg = 2;
+                else if (reg > 15)
                         reg = 15;
                 reg = (reg << 4) | 0x0b;
                 reg_w(gspca_dev, 0x19, &reg, 1);
                 break;
             }
         case SENSOR_OV6650: {
-                __u8 i2c[] = {0xa0, 0x60, 0x11, 0xc0, 0x00, 0x00, 0x00, 0x10};
-                i2c[3] = 30 / fps - 1;
-                if (i2c[3] > 15)
-                        i2c[3] = 15;
-                i2c[3] |= 0xc0;
+                /* The ov6650 has 2 registers which both influence exposure,
+                   first there is register 11, whose low nibble sets the no fps
+                   according to: fps = 30 / (low_nibble + 1)
+
+                   The fps configures the maximum exposure setting, but it is
+                   possible to use less exposure then what the fps maximum
+                   allows by setting register 10. register 10 configures the
+                   actual exposure as quotient of the full exposure, with 0
+                   being no exposure at all (not very usefull) and reg10_max
+                   being max exposure possible at that framerate.
+
+                   The code maps our 0 - 510 ms exposure ctrl to these 2
+                   registers, trying to keep fps as high as possible.
+                */
+                __u8 i2c[] = {0xb0, 0x60, 0x10, 0x00, 0xc0, 0x00, 0x00, 0x10};
+                int reg10, reg11;
+                /* No clear idea why, but setting reg10 above this value
+                   results in no change */
+                const int reg10_max = 0x4d;
+
+                reg11 = (60 * sd->exposure + 999) / 1000;
+                if (reg11 < 1)
+                        reg11 = 1;
+                else if (reg11 > 16)
+                        reg11 = 16;
+
+                /* frame exposure time in ms = 1000 * reg11 / 30    ->
+                reg10 = sd->exposure * 2 * reg10_max / (1000 * reg11 / 30) */
+                reg10 = (sd->exposure * 60 * reg10_max) / (1000 * reg11);
+                if (reg10 < 1) /* 0 is a valid value, but is very _black_ */
+                        reg10 = 1;
+                else if (reg10 > reg10_max)
+                        reg10 = reg10_max;
+
+                /* Write reg 10 and reg11 low nibble */
+                i2c[3] = reg10;
+                i2c[4] |= reg11 - 1;
                 if (i2c_w(gspca_dev, i2c) < 0)
                         PDEBUG(D_ERR, "i2c error exposure");
                 break;