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[linux-dvb] Re: More than 4 DVB cards - again



Hello,

On 06/22/04 10:27, Peter Maersk-Moller wrote:
Seriously, using "extended minor number". How do I do that ?
Are you talking about changing something in a config file
or are you talking about rewriting the device driver ?
This must be changed in the dvb-core device handling.

What is the limitation regarding more DVB devices than 4 ?
There can be 9 different types of devices per adapter (video,audio,sec,frontend,demux,dvr,ca, net) and each device can be present up to 4 times (ie. demux0, demux1, demux2, demux3)

Because everything needs to be a power of two, one adapter consumes 16*4=64 minor numbers. Because of the fact you only have 256 minor numbers you're stuck with 4 adapters.

For 2.4 alone, the devfs implementation wasn't tied to major/minor numbers, so if you used devfs alone it was possible to support more that 4 adapters.

In 2.6 this has changed -- devfs is now more tightly coupled and is limited to major/minor numbers again.

But: major/minor numbers have been extended from 8 to 16 bit types, so it should be possible to support more devices, but this also affects the surrounding system (ie. glibc must support this)

Additionally, udev/sysfs should be support which also overcomes this limitation.

But AFAIK nobody has worked on these problems so far, so ideas and patches are welcome.

Kind regards
--PMM
CU
Michael.




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