WANTED: someone who knows what exactly that ssb thingy is intended/used for

[Fumihito YOSHIDA]

Hi Stefan,

Im not well versed in the subject, but i have some knowledge.

ssb (Sonics Silicon Backplane, in *BSD world, they called "SiBa")
is backplane bus protcol of Broadcom intelligent SoC devices.
// In broadcom terms, "SoC" is included ethernet/wireless ethernet devices.

Your Inspiron 1521(and any other dell's laptop, they use broadcom
onboard ethernet + WLAN) has 2 ssb devices, plz see below diagram;

<PCI or HTr/MuTIOL PCI-bridge chip>
   |PCI|              |PCI|
 <BCM4401-B0>       <BCM4328>
  |ssb(a)|           |ssb(b)|
bcm nic unit        bcm WLAN unit

(guess from heuristics)
Perhaps, when loading b44, that do swallow hungrily ssb(a), ssb(b)
and BCM4401,  the wl cannot get own ssb(b).
(/guess)

So,
> Would a PCI-SSB bridge look different or is Broadcom using the same PCI ID for
> different devices?
Physically yes, they are dirrerent devices, but they have same backends.

> Both drivers clearly match for the same PCI ID and are the only ones to do so.

In other hands, root cause of this complicated contraption, the ssb has
something went wrong behavior[0], but i dont know why...

[0] e.g.: https://bugs.launchpad.net/bugs/333903