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Subject[PATCH] et8ek8: Support for EXPOSURE_ABSOLUTE
To do a good job taking photos, userland needs to be able to query/set
exposure in absolute units. (As scene gets darker, exposure time
should be increased to cca 1/100 second -- based on scene type -- then
sensitivity should be stepped up to maximum reasonable value, only
then time should be increased again). This patch provides neccessary
support.

Signed-off-by: Pavel Machek <pavel@ucw.cz>

---

I have experimental version of sdlcam that can take photos, and this
is the most important missing piece.

diff --git a/drivers/media/i2c/et8ek8/et8ek8_driver.c b/drivers/media/i2c/et8ek8/et8ek8_driver.c
index 256acf73d5ea..82d59691c788 100644
--- a/drivers/media/i2c/et8ek8/et8ek8_driver.c
+++ b/drivers/media/i2c/et8ek8/et8ek8_driver.c
@@ -50,6 +50,8 @@ struct et8ek8_sensor {

struct v4l2_ctrl_handler ctrl_handler;
struct v4l2_ctrl *exposure;
+ struct v4l2_ctrl *exposure_abs;
+ u32 cur_exposure;
struct v4l2_ctrl *pixel_rate;
struct et8ek8_reglist *current_reglist;

@@ -546,6 +548,65 @@ static int et8ek8_reglist_import(struct i2c_client *client,
return 0;
}

+typedef unsigned int fixpoint8; /* .8 fixed point format. */
+
+/*
+ * Return time of one row in microseconds
+ * If the sensor is not set to any mode, return zero.
+ */
+fixpoint8 et8ek8_get_row_time(struct et8ek8_sensor *sensor)
+{
+ unsigned int clock; /* Pixel clock in Hz>>10 fixed point */
+ fixpoint8 rt; /* Row time in .8 fixed point */
+
+ if (!sensor->current_reglist)
+ return 0;
+
+ clock = sensor->current_reglist->mode.pixel_clock;
+ clock = (clock + (1 << 9)) >> 10;
+ rt = sensor->current_reglist->mode.width * (1000000 >> 2);
+ rt = (rt + (clock >> 1)) / clock;
+
+ return rt;
+}
+
+/*
+ * Convert exposure time `us' to rows. Modify `us' to make it to
+ * correspond to the actual exposure time.
+ */
+static int et8ek8_exposure_us_to_rows(struct et8ek8_sensor *sensor, u32 *us)
+{
+ unsigned int rows; /* Exposure value as written to HW (ie. rows) */
+ fixpoint8 rt; /* Row time in .8 fixed point */
+
+ /* Assume that the maximum exposure time is at most ~8 s,
+ * and the maximum width (with blanking) ~8000 pixels.
+ * The formula here is in principle as simple as
+ * rows = exptime / 1e6 / width * pixel_clock
+ * but to get accurate results while coping with value ranges,
+ * have to do some fixed point math.
+ */
+
+ rt = et8ek8_get_row_time(sensor);
+ rows = ((*us << 8) + (rt >> 1)) / rt;
+
+ if (rows > sensor->current_reglist->mode.max_exp)
+ rows = sensor->current_reglist->mode.max_exp;
+
+ /* Set the exposure time to the rounded value */
+ *us = (rt * rows + (1 << 7)) >> 8;
+
+ return rows;
+}
+
+/*
+ * Convert exposure time in rows to microseconds
+ */
+static int et8ek8_exposure_rows_to_us(struct et8ek8_sensor *sensor, int rows)
+{
+ return (et8ek8_get_row_time(sensor) * rows + (1 << 7)) >> 8;
+}
+
/* Called to change the V4L2 gain control value. This function
* rounds and clamps the given value and updates the V4L2 control value.
* If power is on, also updates the sensor analog and digital gains.
@@ -637,18 +698,22 @@ static int et8ek8_set_ctrl(struct v4l2_ctrl *ctrl)
{
struct et8ek8_sensor *sensor =
container_of(ctrl->handler, struct et8ek8_sensor, ctrl_handler);
+ u32 val = ctrl->val;

switch (ctrl->id) {
case V4L2_CID_GAIN:
return et8ek8_set_gain(sensor, ctrl->val);

+ case V4L2_CID_EXPOSURE_ABSOLUTE:
+ val = et8ek8_exposure_us_to_rows(sensor, &val);
+ /* Fall through */
+
case V4L2_CID_EXPOSURE:
{
- struct i2c_client *client =
- v4l2_get_subdevdata(&sensor->subdev);
-
+ struct i2c_client *client = v4l2_get_subdevdata(&sensor->subdev);
+ sensor->cur_exposure = val;
return et8ek8_i2c_write_reg(client, ET8EK8_REG_16BIT, 0x1243,
- ctrl->val);
+ val);
}

case V4L2_CID_TEST_PATTERN:
@@ -662,8 +727,28 @@ static int et8ek8_set_ctrl(struct v4l2_ctrl *ctrl)
}
}

+static int et8ek8_get_ctrl(struct v4l2_ctrl *ctrl)
+{
+ struct et8ek8_sensor *sensor =
+ container_of(ctrl->handler, struct et8ek8_sensor, ctrl_handler);
+
+ switch (ctrl->id) {
+ case V4L2_CID_EXPOSURE_ABSOLUTE:
+ ctrl->val = et8ek8_exposure_rows_to_us(sensor, sensor->cur_exposure);
+ return 0;
+
+ case V4L2_CID_EXPOSURE:
+ ctrl->val = sensor->cur_exposure;
+ return 0;
+
+ default:
+ return -EINVAL;
+ }
+}
+
static const struct v4l2_ctrl_ops et8ek8_ctrl_ops = {
.s_ctrl = et8ek8_set_ctrl,
+ .g_volatile_ctrl = et8ek8_get_ctrl,
};

static const char * const et8ek8_test_pattern_menu[] = {
@@ -697,6 +782,13 @@ static int et8ek8_init_controls(struct et8ek8_sensor *sensor)
v4l2_ctrl_new_std(&sensor->ctrl_handler,
&et8ek8_ctrl_ops, V4L2_CID_EXPOSURE,
min, max, min, max);
+
+ min = et8ek8_exposure_rows_to_us(sensor, 1);
+ max = et8ek8_exposure_rows_to_us(sensor, max);
+
+ sensor->exposure_abs =
+ v4l2_ctrl_new_std(&sensor->ctrl_handler, &et8ek8_ctrl_ops,
+ V4L2_CID_EXPOSURE_ABSOLUTE, min, max, min, max);
}

/* V4L2_CID_PIXEL_RATE */
@@ -738,8 +830,12 @@ static void et8ek8_update_controls(struct et8ek8_sensor *sensor)
*/
pixel_rate = ((mode->pixel_clock + (1 << S) - 1) >> S) + mode->width;
pixel_rate = mode->window_width * (pixel_rate - 1) / mode->width;
+ __v4l2_ctrl_modify_range(sensor->exposure, 1, max, 1, max);
+
+ min = et8ek8_exposure_rows_to_us(sensor, 1);
+ max = et8ek8_exposure_rows_to_us(sensor, max);
+ __v4l2_ctrl_modify_range(sensor->exposure_abs, min, max, min, max);

- __v4l2_ctrl_modify_range(ctrl, min, max, min, max);
__v4l2_ctrl_s_ctrl_int64(sensor->pixel_rate, pixel_rate << S);
}


--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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