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DVB USB: change USB stream settings dynamically

I was planning make DVB USB be able to switch USB streaming parameters dynamically. I mean [struct usb_data_stream_properties] parameters.

Currently it reserves USB streaming buffers when device is plugged. Own buffer is reserved for each frontend, which means currently 1-3 streaming buffers depending on device.

Basically I see USB TS as a DVB USB device property - not property of frontend. USB TS is interface between computer and USB-bridge and amount of parallel USB TS or TS configurations depends on USB-bridge capabilities. Sometimes used USB TS could be configured to fit better used stream. Smaller buffers for the narrow radio stream and biggest buffers for the wide DVB-S2 stream.

I was wondering how to resolve that situation? It is not very big problem currently but I still want to make it better as there is surely coming new devices that needs better control for the USB streaming parameters. Currently there is mxl111sf driver which seems to offer 6 different streaming configurations but AFAIK only three is currently used as there is 3 frontends and each one has own streaming parameters - and buffers - even only one can be used at the time.

1. Configure streaming parameters (alloc buffers) every time when streaming is started? IIRC that causes some problems lately for em28xx as memory goes dis-coherent and buffers cannot allocated.

2. Allocate buffers (streaming configuration) for all needed device use configurations at very beginning. Then add some logic to map streaming config to frontend at runtime. That is quite near what mxl111sf does currently.

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