This is a historic thing.
USE_GENERIC_RW uses the Linux page cache for read/write. This means that the Linux generic_read and generic_write functions are used which and YAFFS supplies the read_page write_page calls.

Not defining USE_GENERIC_RW directly implements read/write without using the page cache.

The direct read/write stuff was iimplemented first, and I followed it by generic read/write when memory mapping was implemented. During the transition both options worked. Things have now moved on and not defining USE_GENERIC_RW is broken, with no real motivation to fix it. 

Ie. You should always define USE_GENERIC_RW. 

This comes up every couple of months on the list. I guess I should pull it out.


-- Charles




-----Original Message-----
From: yaffs-admin@stoneboat.aleph1.co.uk [mailto:yaffs-admin@stoneboat.aleph1.co.uk] On Behalf Of Ulla
Sent: Thursday, 14 October 2004 11:40 a.m.
To: yaffs@stoneboat.aleph1.co.uk
Subject: [Yaffs] CONFIG_YAFFS_USE_GENERIC_RW


Hi,

I am using yaffs (CVS) (linux 2.6.8.1, mtd-snapshot: 20041005), and I am able 
to mount the device properly, to write to the flash and erase from the flash. 
But with CONFIG_YAFFS_USE_GENERIC_RW disabled copying back (or cat) doesn't 
work, it is running in an endless loop. For example, catting a simple text 
file will endlessly repeat the contents of that file.  Copying a file will 
not end & create a huge file at the destination.  By enabling 
CONFIG_YAFFS_USE_GENERIC_RW everything is ok. Can someone explain what are 
the benefits of disabling CONFIG_YAFFS_USE_GENERIC_RW (like it is in the 
default Makefile) and what are the exact differences between generic_rw and 
yaffs_rw?

Thanks a lot
   Ulla
-- 
Bluewater Systems Ltd - ARM Technology Solution Centre

        Ulrike Eisenmann                        Bluewater Systems Ltd
Phone: +64 3 3779127 (Aus +1 800 148 751)       Level 17, 119 Armagh St
Fax:   +64 3 3779135                            PO Box 13889
Email: ulla@bluewatersys.com                    Christchurch
Web:   http://www.bluewatersys.com              New Zealand

_______________________________________________
yaffs mailing list
yaffs@stoneboat.aleph1.co.uk http://stoneboat.aleph1.co.uk/cgi-bin/mailman/listinfo/yaffs