Anyone knows what is the etimology for softc? What does it mean? Where does it come from? When was it first used? In PDP-11 context, CSR means "control and status register". Often there was an address (for a 16-bit word) that was for control and status, and another one for data. For example, the DL-11 (and DLV-11 on QBUS) had a receive CSR at 177560, and receive data at 177562*. I have always interpreted softc as "software c(control/status)", being data that the driver keeps state on, but which is not stored in the hardware. I remember softc being present in 2.8BSD, probably mid 80s, and I would guess that it was introduced very early in the BSD days, in the original networking code. serial devices don't need so much state, and the information that is in the softc in a network device (queues, etc.) are in the tty structure, roughly analogous to the common ethernet data structure. * http://www.fpns.net/willy/pdp11/pdptrbsh.htm (seems accurate from my memory)
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