Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [GIT PATCH] char/misc patches for 3.10-rc1 | Date | Mon, 29 Apr 2013 23:22:18 +0200 |
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On Monday 29 April 2013, Linus Torvalds wrote: > On Mon, Apr 29, 2013 at 1:50 PM, Arnd Bergmann <arnd@arndb.de> wrote: > > > > Fair enough. Of course the distinction here is not based on what it > > does, but how it gets used. > > Even technically, a "bus" generally has a topology. It has addresses, > and it has a protocol. > > i2c is a bus. PCI is a bus. And something like SSB is a bus. There is > a protocol, there's device with identity on the bus, there's stuff > going on.
Right. I was looking at it from the linux driver model perspective, where we already call a lot of things a bus that are not at all one in the engineering sense.
> The SBBI driver has neither addresses nor a protocol. It's literally > just an embedded on-chip serial device as far as I can tell. There's > nothing "bus" about it. It's just a hose. > > Yeah, yeah, at some point you can call "anything" a bus. I could call > my little two-seater car a "school bus", because it has wheels, it's > even yellow exactly like the school buses around here. And I can put a > child in it. So my little yellow two-seater must be a bus too. It's > all just how you define your words. > > But it's a damn big reach. I didn't use to call the serial line > connecting my computer to the modem a "bus". Even if it connected two > devices.
It seems I looked too briefly. As you point out and David already confirmed, there is only one device on the other side, which is indeed a major difference to e.g. SPI, which seems rather similar otherwise but can use chip-select pins to multiplex between different endpoints. Certainly this hardware could do the same, but you are right that it's not relevant because it doesn't do that in practice.
Arnd
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