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List:       openbsd-misc
Subject:    Autoconf
From:       "Ishan Mandrekar" <imandrekar () hotmail ! com>
Date:       2003-02-04 6:13:16
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Hi all,

I'm trying to write a pseudo driver that has to interface with the 
high-level audio driver. I've been facing some problems getting my driver to 
attach to high-level audio driver. I went through the autoconfiguration 
documentation for NetBSD where they lay-out the fashion in which the kernel 
probes and calls the attach routines of drivers listed in the character 
device table to allocate memory for their soft_c structures. The 
documentation also talks about cfattach and cfdriver stuctures as a means of 
conveying to the kernel, parameters such as the size of your soft_c 
structure needed for malloc purposes.

But, when I see the code for other sample pseudo drivers such as pty 
(/sys/kern/tty_pty.c), I see a completely different implementation. Here the 
memory for the soft_c structure is allocated in its attach routine itself 
and the cfattach and cfdriver structures are missing.

I've seen different declarations for the attach routine too. In some driver 
its as simple as:
void <drv_name>_attach (int num);
while in other cases its more akin to the documentation, i.e.
void <drv_name>_attach (struct device *, struct device *, void *);

Could someone please elaborate on how exactly the autoconfiguration works? 
Also, my kernel is currently crashing when the high-level driver that I 
attach to calls config_search() with one of the struct device * passed as an 
argument to it. I'm thinking there is some issue of memory, coz its an 
assignment statement inside the config_search() routine thats failing. Any 
comments on what could be going wrong and how to rectify the error will be 
thoroughly appreciated.

thanks for your time,
-Ishan.





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