DSP Gateway was developed by Nokia for the Maemo Internet Tablets. It's the oldest and more open of the implementations. The open code consists not only of the Linux kernel side, but also the DSP operating system. Unfortunately the development is essentially halted.
It works on OMAP1 and OMAP2, it's production ready, used on the Nokia N800 and N810, it follows Linux standards and it's close to upstream acceptance. There's code for OMAP3 but it hasn't been thoroughly tested.
It is maintained by Hiroshi DOYU.
There are a few user space applications that use it. Essentially GStreamer Nokia DSP plug-ins and a few others developed by the Maemo community.
tidspbridge originally developed by TI, after its release in open source it has received many more contributions, from TI and Nokia.
It is stable and production ready (phone announced at 2009 CES), but it still doesn't meet Linux coding standards although there has been a lot of progress. Only the ARM side is available as open source; unlike the dsp-gateway, the DSP side is completely closed.
TI and the community are working on how power management must be handled, all the effort is being focused on linux-omap-pm branch maintained by Kevin Hillman.
It's under heavy code cleanup to be open source friendly. Originally maintained at omapzoom.org, Hiroshi DOYU started his tree at gitorious, but now Ameya Palande took over.
There are plans to share the mailbox and iommu that the dsp-gateway uses, whenever they are stable and have the full set of features supported by tidspbridge custom implementations, as well as to move parts of it to user-space.
There are slightly more user-space applications using it, including gst-openmax and gst-goo through TI's OpenMAX IL implementation which is also open source.
For documentation and project overview, visit: TI DSP/Bridge project
A slimmer version of the dsp-bridge targeted for the DaVinci platform also developed by TI. It supports a wider variety of chips, not only OMAP.
It is the one farther from meeting Linux standards. The code hasn't even been submitted for reviewing nor is planned to to be merged at any time.
It's tightly tied to CodecEngine and DMAI, and there are GStreamer plug-ins provided by TI to use the algorithms.