> Acked-by: Rob Landley <rob@xxxxxxxxxxx> Thanks. > What is this *note thingy:: syntax? It recurs a lot. Some sort of > reference into the PDF you started out with a link to, maybe? My documentation is texinfo and this is the ASCII output, manually split into different files. I fixed some of the internal references when I noted them. But since it's manual work, I didn't do it carefully. I suspect I'll need to V2 for some reason anyways. > A basic concept of this framework is that you have a 70x75 PCB? Is this > part of that ANSI-VITA standard? Yes. the form-factor is fixed, like PC104 in the PC world. Here's the jpg of a carrier: http://www.ohwr.org/attachments/download/552 (from http://www.ohwr.org/projects/spec/wiki). And here's the jpg of a mezzanine: http://www.ohwr.org/attachments/download/833/FmcAdc100M14b4cha_top_small.JPG You find more on the net, also from commercial vendors. >> +FMC, as such, is not a bus in the usual meaning of the term, because >> +most carriers have only one connector, and carriers with several >> +connectors have completely separate electrical connections to them. >> +This package, however, implements a bus as a software abstraction. > > USB is point to point connections with switches in between. It's still > got B in the acronym. I'm not sure what you're saying here. FMC has no switches, no hotplug, not even shared wires like ISA. I took a while to explain some hardware guys that it ought to be a "bus" in software. That's why I have the paragraph. >> +What is SDB >> +*********** >> + >> +SDB (Self Describing Bus) is a set of data structures that we use for >> +enumerating the internal structure of an FPGA image. We also use it >> as >> +a filesystem inside the FMC EEPROM. > > Are you trying to document infrastructure to implement a standard, or a > bespoke driver for a specific piece of hardware? How much of this is > generic? Are there other vendors who might someday want to use this > code? SDB is already implemented and is generic. We enumerate the devices inside the FPGA already, and it only costs a few lines of VHDL (using the support files by Wesley Terpstra) to describe your own FPGA design. Wesley even discovers and enumerates devices over the Ethernet, by means of Ethernet-driven device access and SDB-aware host code -- all code is published. The SDB specification is discussed in a mailing list and is public (http://www.ohwr.org/attachments/download/1486/sdb-1.0.pdf). By having 64-bit vendor identifiers we encourage anyone who finds SDB useful to become a vendor. There are a few vendors already, although I admit the early adopters are involved in the same set of projects. > Anyway, no serious objection, but I note that reading to this point I > didn't feel I had enough information to wrap my head around what it's > for. It's documentation by people who already know this stuff, for > people who already know this stuff. (There's a long tradition of that. > Oh well.) I'm aware of this. But it's the same if you read USB documentation without ever seeing one such device (I remember the feeling :). FMC is not common on the shelf, but it is already renown in high-profile I/O environments. Thanks /alessandro -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
