question about creating char device in 2.4

question about creating char device in 2.4

[Chris Friesen]

A coworker of mine had created a character device for 2.2 and is now 
looking into porting it forward to 2.4 but he's running into some issues 
with the new generic io code.

Basically he impemented a virtual device that had a fixed amount of 
buffer space.  You could write to/read from that storage space as usual, 
with the one exception that once it was full you could continue to write 
to it and the writes would succeed.

Basically the ideas was to create something that you could log to and 
only the first x bytes would be logged.  After that the writes would 
still succeed but the data would be thrown away. "cat"ing the file would 
then give you the first x bytes that had been stored.

How would you go about hooking in to the 2.4 char device code to do 
something equivalent?

Thanks,

Chris

-- 
Chris Friesen                    | MailStop: 043/33/F10
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Re: question about creating char device in 2.4

[Jonathan Corbet]

> How would you go about hooking in to the 2.4 char device code to do 
> something equivalent?

Linux Device Drivers has a great deal of discussion on portability between
2.2 and 2.4; it also has example code which could be easily adapted to
create your "finite capacity bit bucket" device.  It's available online at
http://www.xml.com/ldd/chapter/book/index.html, but, of course, you'll want
to go and buy at least three copies for your desk...

jon

Jonathan Corbet
Executive editor, LWN.net
corbet@lwn.net