[linux-dvb] Re: V4 API Implementation Q's

[Rob.McConnell@Zarlink.Com]

> Rob.McConnell@Zarlink.Com wrote:
> >
> > Having had a quick look at the code, I cannot see where we perform
checks
> > on the allocation of feeds/filters.  What I mean is there doesn't seem
to
> > be any code that checks to ensure that there are enough underlying h/w
> > filters left to allocate when someone open's up an fd on the demux
device.
> > If it is there, then could you point me in the right direction - thanks
: )
> >
> Well, this is the way we designed it. It fits our application's
> use of resources -- we don't grab them in advance to "reserve" them,
> we allocate resources when we need them and release them when
> we are done with them. So it does not make a difference if open()
> fails or ioctl(SET_FILTER) fails.

> Johannes

Hi Johannes,

Been a while since we spoke last  ; ^ )

Anyway, just to get it straight, when we open the demux device in read mode
to obtain an fd (and to allocate memory for the feed/filter), we won't be
performing any checks on the overall number of filters in the system.  When
we perform the IOCTL to actually setup a feed/filter, this is where the
underlying hardware will be checked to see if there are any available PID
filters left and then an error can be returned to indicate if no
filters/feeds are available.  Is this correct?

BTW, have we had any comments off our other STB friends as regards to the
V4 API?  Does it meet their requirements as well?

I'm still curious as to why the output device (OD) proposal was thrown
away.  It just seemed logical to have individual ODs so that you could open
them and immediately know whether the resources were available.  Then you
could have IOCTLs specific to each device, making the design more
object-oriented.

In fact, this is what I have currently implemented in the HAL code for my
current project.  I have a separate class for each possible type of feed
(general purpose, section table, audio decoder, video decoder, teletext
decoder, subtitle decoder, etc.)  with each specific feed inheriting from a
feed superclass.

That's all for now,

Rob : )




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