Hi Baruch,

On 24/02/14 20:38, Baruch Siach wrote:

On Mon, Feb 24, 2014 at 06:35:16PM +0100, Sylwester Nawrocki wrote:

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This patch adds subdev driver for Samsung S5K6A3 raw image sensor.
As it is intended at the moment to be used only with the Exynos
FIMC-IS (camera ISP) subsystem it is pretty minimal subdev driver.
It doesn't do any I2C communication since the sensor is controlled
by the ISP and its own firmware.
This driver, if needed, can be updated in future into a regular
subdev driver where the main CPU communicates with the sensor
directly.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>

[...]

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+static int s5k6a3_open(struct v4l2_subdev *sd, struct v4l2_subdev_fh *fh)
+{
+	struct v4l2_mbus_framefmt *format = v4l2_subdev_get_try_format(fh, 0);
+
+	*format		= s5k6a3_formats[0];
+	format->width	= S5K6A3_DEFAULT_WIDTH;
+	format->height	= S5K6A3_DEFAULT_HEIGHT;
+
+	return 0;
+}
+
+static const struct v4l2_subdev_internal_ops s5k6a3_sd_internal_ops = {
+	.open = s5k6a3_open,
+};

Where is this used?

This will be called when user process opens the corresponding /dev/v4l-subdev*
device node. More details on the v4l2 sub-device interface can be found at [1],
[2]. The device node is created by an aggregate media device driver, once all
required sub-devices are registered to it.
The above v4l2_subdev_internal_ops::open() implementation is pretty simple,
it just sets V4L2_SUBDEV_FORMAT_TRY format to some initial default value.
That's a per file handle value, so each process opening a set of sub-devices
can try pipeline configuration independently. 

[1] http://linuxtv.org/downloads/v4l-dvb-apis/subdev.html
[2] http://linuxtv.org/downloads/v4l-dvb-apis/vidioc-subdev-g-fmt.html

Regards,
Sylwester