Author's comments concerning the '8139regs.c' debugging aid

This module creates a pseudo-file in the '/proc' directory that lets
users see current values in the most significant RealTek-8139 NIC's 
registers by simply typing the command: 

		       $ cat /proc/8139regs

Here is what the resulting display will look like:

---------------------------------------------------------------------


               RealTek-8139 Network Controller register-values 

       CR=0D    TCR=77000680   RCR=0000F78E     MAC=00:50:BF:E9:28:A9 

        TSD0=8008A062   TSD1=8008A062   TSD2=8008A062   TSD3=8008A062 
       TSAD0=3789C000  TSAD1=3789C600  TSAD2=3789CC00  TSAD3=3789D200 

       RBSTART=378A0000  CAPR=DD28  CABR=DD38     ERBCR=0000  ERSR=0A 

       IMR=C07F   MULINT=0000    TSAD=F00F    REC=00  DIS=00  FCSC=00 


---------------------------------------------------------------------

This module can coexist with other network-drivers for the RTL-8139
(such as the '8139too.c' driver distributed with Linux or any driver
we are bulding as a course-project), because it does not modify any
of the RTL-8139 registers.  It omits displaying ISR (the Interrupt 
Status Register) because reading that register has the 'side-effect' 
of clearing it, thus potentially intefering with a network driver's 
interrupt-handler routine.

It is perhaps useful to RealTek-8139 network-driver developers as a 
reverse-engineering tool, or as a debugging aid, since it exhibits,
in the above display for example, how the registers were configured 
by the official Linux '8139too.c' network-driver, and thus allows a 
comparison with the values we may be programming in our own driver.

Allan Cruse
10 Nov 2010