On Friday 23 July 2010 15:01:29 Laurent Pinchart wrote:
> Hi everybody,
>
> Trying to implement support for multiple sensors connected to the same OMAP3
> ISP input (all but one of the sensors need to be kept in reset obviously), I
> need to associate host-specific data to the sensor subdevs.
>
> The terms host and bridge are considered as synonyms in the rest of this e-
> mail.
>
> The OMAP3 ISP platform data has interface configuration parameters for the two
> CSI2 (a and c), CCP2 and parallel interfaces. The parameters are used to
> configure the bus when a sensor is selected. To support multiple sensors on
> the same input, the parameters need to be specified per-sensor, and not ISP-
> wide.
>
> No issue in the platform data. Board codes declare an array of structures that
> embed a struct v4l2_subdev_i2c_board_info instance and an OMAP3 ISP-specific
> interface configuration structure.
>
> At runtime, when a sensor is selected, I need to access the OMAP3 ISP-specific
> interface configuration structure for the selected sensor. At that point all I
> have is a v4l2_subdev structure pointer, without a way to get back to the
> interface configuration structure.
>
> The only point in the code where the v4l2_subdev and the interface
> configuration data are both known and could be linked together is in the host
> driver's probe function, where the v4l2_subdev instances are created. I have
> two solutions there:
>
> - store the v4l2_subdev pointer and the interface configuration data pointer
> in a host-specific array, and perform a an array lookup operation at runtime
> with the v4l2_subdev pointer as a key
>
> - add a void *host_priv field to the v4l2_subdev structure, store the
> interface configuration data pointer in that field, and use the field at
> runtime
>
> The second solution seems cleaner but requires an additional field in
> v4l2_subdev. Opinions and other comments will be appreciated.
There is a third option: the grp_id field is owned by the host driver, so you
could make that an index into a host specific array.
That said, I think having a host_priv field isn't a bad idea. Although if we
do this, then I think the existing priv field should be renamed to drv_priv
to prevent confusion.
Regards,
Hans
--
Hans Verkuil - video4linux developer - sponsored by TANDBERG, part of Cisco
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