Messages in this thread | | | Date | Wed, 06 Dec 2006 17:27:49 -0500 | From | Kristian Høgsberg <> | Subject | Re: [PATCH 0/3] New firewire stack |
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Stefan Richter wrote: ... >> Another point is the various streaming drivers. There used to be 5 different >> userspace streaming APIs in the linux1394: raw1394, video1394, amdtp, dv1394 >> and rawiso. Recently, amdtp (audio streaming) has been removed, since with >> the rawiso interface, this can be done in userspace. However the remaining 4 >> interfaces have slightly disjoint feature sets and can't really be phased out. > > The old iso API of (lib)raw1394 has been marked deprecated and > undocumented in libraw1394's documentation for some time, and will go > away in 2007. > > Dv1394 might go away in 2007 too if there is enough effort to move > high-profile users over to rawiso a.k.a. the current iso API of > (lib)raw1394. > > I suppose video1394 might get a viable migration path with your new > driver, if you and interested developers put effort into development > (and help with deployment) of a proper replacement.
As discussed on linux1394-devel, it may be possible to do a thin video1394 compatibility driver for this one, but since the biggest user of this interface is libdc1394, it is probably better to just write a new iso streaming backend for this library. libdc1394 already supports different streaming backends. For non-libdc1394 users of video1394, the interface I'm providing is very close to the video1394 ioctl interface, so porting should be easy enough.
>> In the long run, supporting 4 different interfaces that does almost the same >> thing isn't feasible. The streaming interface in my new stack (only >> transmission implemented at this point) can replace all of these interfaces. > > You have to look at the matter not only from the POV of API design but > also of deployment and support.
My POV here *is* about deployment and support, but from the kernel side of things. If you commit yourself to long time support for the firewire stack, would you prefer 4 slightly different streaming drivers with different user space interfaces, or just one userspace driver with one userspace interface, that enables the 4 different types of streaming to be done in userspace? The design of the streaming interfaces have been focused on enabling all these ad-hoc, in-kernel drivers to move to userspace, to make it feasible to actually support the stack.
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