Hello everyone when we need to setup media pipeline, eg, for camera capture, media-ctl needs to be called multiple time to setup media link and subdev formats, or similar code in a single application. this will use multiple IOCTLs on "/dev/mediaX" and "/dev/v4l2-subdevY". to setup media pipeline in userspace requires to fully understanding the topology of the media stack. but the fact is only media driver developer could know how to setup media pipeline. each time driver updates, this would break userspace application if application engineers don't know this change. In this case, if a IOCTL is designed to setup media pipeline, no need to update applications, after driver is updated. this will not only benefit for design a single IOCTL, this also helps to hide the detail of media pipeline, by load a binary blob which holds information about how to setup pipeline, or hide it in bootloader/ACPI tables/device tree, etc. another benefit is save time for setup media pipeline, if there is a PKI like "time for open camera". as my test, this will saves hundreds of milliseconds. is this acceptable? BR. Ning.
