seq_file / proc_fs userdata issue

[John Belmonte]

The proc_fs interface supports userdata, which can be used for an
object-oriented style of programming.  Used intelligently, this can
eliminate a fair amount of code redundancy in drivers that handle many
proc files.

Recently there has been work on the kernel to convert proc reads to use
seq_file.  The problem is, although seq_file also has userdata support,
the userdata given to proc_fs is not automatically propagated to
seq_file.  The only way to set the seq_file userdata is in the open
handler, which as far as I can tell does not have access to the
proc_dir_entry.  The result is a proliferation of nearly-identical
functions and tables that could otherwise be generalized.

In summary, I'm suggesting that the proc_fs internals automatically
propagate the userdata placed in the proc_dir_entry to the seq_file 
instance, so that it is available in the read handler.  After all, this 
is what we enjoyed before the move to seq_file.

Regards,
-John Belmonte