Re: Multiple device attachments

[Frank Zerangue <frank.zerangue%gmail.com@localhost>]

Thanks --

On Jul 21, 2011, at 3:18 PM, Michael wrote:

> Hello,
> 
> On Thu, 21 Jul 2011 14:44:04 -0500
> Frank Zerangue <frank.zerangue%gmail.com@localhost> wrote:
> 
>> /sys/device.h -- seems to indicate that a device driver can attach to 
>> multiple parent
>> drivers (e.g. busses, controllers, ?)
>> 
>> /*
>> * Devices can have multiple configuration attachments if they attach
>> * to different attributes (busses, or whatever), to allow specification
>> * of multiple match and attach functions.  There is only one configuration
>> * driver per driver, so that things like unit numbers and the device
>> * structure array will be shared.
>> */
>> 
>> Does anyone know how this is done in practice?
> 
> You split the driver in bus-dependent and bus-independent portions - the 
> former does stuff like match & attach, find and map registers etc., the 
> latter is the actual driver. There are plenty examples in the source tree:
> - hme, gem exist as pci and sbus variants
> - le, esp, com have lots of different bus backends ( Try to find a 1990s UNIX 
> workstation that has neither an le nor an esp. Suns used both as sbus 
> devices, others used their own buses or had them embedded in custom IO chips. 
> )
> - chipsfb and igsfb supports both pci and ofbus ( actually vlb with 
> OpenFirmware glue, see arch/shark/ofw/chipsfb_ofbus.c, igsfb_ofbus.c )
> 
> have fun
> Michael
> -- 
> Michael <macallan%netbsd.org@localhost>