RE: [ECOS] eth device drivers

["Trenton D. Adams" <tadams at extremeeng dot com>]

It would be ok to just say to use it, but I would still like to know
what all the parameters to it should be.  There's a little bit of an
explanation of DEVTAB_ENTRY in the eCos Reference Manual, but nothing on
ETH_DRV_SC.

That still doesn't answer all of my questions though.

Does ETH_DRV_SC create the edb7xxx_sc variable used by NETDEVTAB_ENTRY?

When you don't answer a question directly should I assume that I'm
correct in my deductions?

> -----Original Message-----
> From: jlarmour@cambridge.redhat.com 
> [mailto:jlarmour@cambridge.redhat.com] On Behalf Of Jonathan Larmour
> Sent: Thursday, June 14, 2001 3:14 PM
> To: Trenton D. Adams
> Cc: 'eCos'
> Subject: Re: [ECOS] eth device drivers
> 
> 
> "Trenton D. Adams" wrote:
> > 
> > Do I have to write a driver for the actual modem, and one for the 
> > network portion of it, or should it all be integrated into 
> one?  Right 
> > now I'm looking at 
> "devs\eth\arm\edb7xxx\current\src\if_edb7xxx.c".  
> > It looks to me like it's the only driver file for that 
> network device.  
> > Is this correct?
> 
> For the CS8900 on the edb7211, yes.
>  
> > How do I go about understanding the driver?  For instance, 
> what good 
> > does it do to go
> > 
> > NETDEVTAB_ENTRY (edb7xxx_netdev, "edb7xxx", edb7xxx_cs8900_init, 
> > &edb7xxx_sc); ???
> > 
> > Doesn't that device tab entry have to be put inside a table 
> somewhere 
> > in the kernel in order for the kernel to access it, or to even know 
> > it's there?  Or does the CYG_HAL_TABLE_ENTRY part of the 
> macro create 
> > a string that "make" somehow parses, and automatically puts 
> the entry 
> > into an array somewhere in the kernel as it's being made 
> and compiled?
> 
> CYG_HAL_TABLE_ENTRY puts things into a special ELF section. 
> The object file containing the driver (and the table entry) 
> is forcibly linked into the application by having the object 
> sucked in by the linker script. This happens because of the 
> "compile -library libextras.a if_edb7xxx.c" which places the 
> object in libextras.a, and at the end of the build process 
> all of libextras.a is converted to a single object extras.o.
>  
> > Does ETH_DRV_SC create the edb7xxx_sc variable used by 
> > NETDEVTAB_ENTRY? That's what it looks like in the eCos sources.  Is 
> > there documentation for all this stuff, or does everyone 
> have to look 
> > through the source like me?  It would be nice to just have 
> docs that 
> > say something like "ETH_DRV_SC creates a structured vairable of the 
> > type 'eth_hwr_funs' and fills it with all the function names, etc".
> > 
> > With documentation like that, I wouldn't care about what the MACROS 
> > were doing, I would just use them.
> 
> What if the documentation said just to use them rather than 
> to say what they did, which is an implementation detail :-). 
> And as you can maybe guess from the above description, the 
> implementation is more detailed than people would want to know about!
> 
> Jifl
> -- 
> Red Hat, Rustat House, Clifton Road, Cambridge, UK. Tel: +44 
> (1223) 271062 Maybe this world is another planet's Hell 
> -Aldous Huxley || Opinions==mine Come to the Red Hat 
> TechWorld open source conference in Brussels!
> Keynotes, techie talks and exhibitions    
> http://www.redhat-techworld.com/
>