[linux-dvb] Re: dvb-kernel CVS branched for Linux 2.4

[Michael Hunold <hunold@convergence.de>]

Hello Jeremy,

please remember:

1. DVB (aka the dvb core) does not equal dvb-ttpci (aka saa7146/av7110 
driver). "DVB" nearly always means dvb-ttpci, but "dvb-kernel" has much 
more drivers (Skystar2, Twinhan, USB thingies) that never went into "DVB".

2. The DVB API version 3 won't be changed, ie. the backward 
compatibility from a userspace point of view is guaranteed

3. "dvb-kernel" is relatively stable, and you have a working 2.4 branch 
of it that will continue to live.

4. Manpower is a scarce resource.

On 04/21/04 15:03, Jeremy Hall wrote:
> If you can guarantee me that features and functionality worked on in 2.6 
> that are reasonably 2.4 compliant will get ported to the 2.4 tree then I'm 
> ok with it
See 2 and 3

> but if you have features and bug fixes that are DVB related, but not 
> architecture dependent, I.E. bootstrapping 2.6 stuff, then I have a real 
> problem.  Maintaining two separate code trees without dilligence means 
> that whomever is NOT on HEAD branch ultimately loses.
See 1 and 2

> If the code before the split works both in 2.4 and 2.6, then why is that 
> not satisfactory to include in mainline?
Because 2.4 != 2.6. I get regularly bashed on the Linux kernel mailing 
list, because the DVB subsystem has some very rough edges. The thing is 
now in the mainline kernel, so I think we need to play Linus' rules. -- 
and support important improvements that need large changes in the 
codebase. But remember 2

> What were the historical reasons for using a single tree for 2.4 and 2.6? 
None. It simply worked. The main reason was that the Video4Linux part of 
dvb-ttpci was ported to my new modularized saa7146 layer, in order to 
remove code duplication and have a maintained Video4Linux subsystem for 
DVB again.

> What has changed since then philisophically to cause that decision to be 
> revoked without warning?
See 3 and 4

> For many months, I thought dvb was for 2.4 and dvb-kernel was for 2.6.  I 
> was surprised to see that dvb-kernel was also for 2.4 and gleefully 
> switched to it.  I suspect people don't realize that dvb-kernel works in 
> 2.4.
dvb-ttpci/vdr users really don't notice the difference, but most 
budget-card users already use "dvb-kernel" for a long time.

> Just because it isn't easy IMHO is not justification not to do it.  
See 4

> Perhaps the CVS code could be marked up in some way such that when the 
> code is exported to the kernel, an automated process could remove the 
> unwanted segments I.E. 2.4 compatability.
In theory that's possible. But in practice, it's already hard to fix and 
improve existing drivers if you don't have the proper hardware lying 
around. Remember some developers do this in their spare time, 
maintaining everything for 2.4 and 2.6 means double work.

> _J
Nobody will be cut off, "DVB" and "dvb-kernel" (branch) can be used for 
2.4, "dvb-kernel" for 2.6. The DVB v3 API won't be changed. We all have 
limited time, but everybody is free to participate in this project and 
improve things. 8-)

CU
Michael.


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