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>

diff --git a/drivers/media/video/gspca/sonixb.c b/drivers/media/video/gspca/sonixb.c
index c0ce21f..7303df0 100644 (file)
--- 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;