Hi, I am doing some preliminary scouting of how one could add support for FICON (FC-SB-3 specifically). I am mostly interested in Linux being able to act as a FICON target for now.
The TL;DR summary for FICON is that it uses Fibre Channel just like FCP/SCSI up to but not including the FC-4 (FCP) layer. At that point it uses its own SBCCS layer. FICON is used by IBM mainframes to interface peripherals like tape, disk, printers, card punchers/readers, etc. It is more like a mainframe USB/Firewire than SCSI in that regard. I would prefer to implement my peripherals in user-space, I don't see any convincing case for having e.g. a virtual tape drive running in kernel space. The I/O heavy disks would probably benefit from being in kernel space, but I am OK limiting the initial scope. I am 100% new to the SCSI and Fibre Channel subsystem in Linux, and I do not even know if the current HBAs support sending frames without FCP but after scouting the code it does seem that it might work out - FCP seems decoupled enough. If you want to learn more the standard document Wireshark has an implementation of the protocol (packet-fcsb3.c/h). If you want all the details you will sadly have to pay $60 and buy it from INCITS at https://webstore.ansi.org/Standards/INCITS/INCITS3742003S2013. Fwiw, FICON uses FC type 0x1B and 0x1C. Any thoughts or ideas where you would start? Do you see any future for this addition to the kernel? Thanks in advance, Chris
