Re: Multiple device attachments

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

The examples you site seem to indicate that for example the le device may 
attach to many
alternative devices (e.g. pci, tc, …), but only one attachment is made when 
autoconf is complete. I may have 
read the code examples incorrectly -- please pardon me if I did; but what I 
want to know is --  can a 
device have multiple attachments (more than one parent device) when autoconf is 
complete. 

Thanks,
Frank

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>