On Tue, Apr 19, 2011 at 03:58:32PM +0200, Arend van Spriel wrote: > On Sun, 17 Apr 2011 19:38:12 +0200, Arnd Bergmann <arnd@xxxxxxxx> wrote: > > Hi RafaÅ, > > As you probably expected I tried to integrate and use your bcmai/bcmaxi/? > driver with our brcm80211 driver (making progress). In the mean time > I tried to follow the discussions going on, but I am still catching > up. > > >Compare this to the PCI bus type, which essentially deals with devices > >that have a PCI configuration space that contains generic (irq, memory, > >vendor/device ID, ...) registers along with device specific registers. > > How much alike is the (BCM)AXI bus type? My assumption was that each > registered PCI device is handled by a single driver module. In the > current(?) bcmai implementation each device driver is called with the > appropriate device structure reference, but it will also have the bus > structure reference and through that can also access other cores on the > (bcm)axi bus. This seems to me a potential issue when there are no > synchronization mechanisms in place (whether in a SoC configuration or > PCI-hosted). Does the PCI bus type allow driver for device A access > device B? > > >A new bus_type really only makes sense if you expect a lot of devices > >to use this and you want to have the probing in the bus. If you only > >want to have a way to enumerate devices that get created by the > >parent driver, you can also use platform devices. > > The main assumption of the (bcm)axi driver seems to be that each core can > be considered as a device. Correct me if I am wrong, but I consider a > device to be an entity providing a particular system function. So an > ethernet device provides ethernet connectivity function, a mixer device > provides sound mixing function, and so on. The cores within a chip are not > always self-contained like this. To clarify let's say a system function is > realized by programming core A, core B, and finally trigger core A to set > the function in motion. This implies the need of coordination between the > programming steps on those cores. > > Is my view on what is a device wrong? Does a platform device differ in > this respect from a regular device? Please don't use a platform device, unless there is no other way for your device to work. For this device, you are connected to the PCI bus, so a platform device does not make sense at all. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
