From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from web58702.mail.re1.yahoo.com ([66.196.100.124]) by canuck.infradead.org with smtp (Exim 4.63 #1 (Red Hat Linux)) id 1HDv6N-0002fa-Lr for linux-mtd@lists.infradead.org; Sun, 04 Feb 2007 23:05:17 -0500 Date: Sun, 4 Feb 2007 19:58:29 -0800 (PST) From: Philip Rakity Subject: Do not understand use of oobfree To: linux-mtd@lists.infradead.org MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Message-ID: <872380.68552.qm@web58702.mail.re1.yahoo.com> List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , When reading the documentation for nand flash I realized that there was an out of band area of some size following each page. This size could be say 8, 16 or 64 bytes. Inside this oob area is stored a bad block marker. There may also be stored ecc bytes. And there is of course some area not used. Some Questions: a) the location and size of the ecc bytes are determined by what ? .useecc = MTD_NANDECC_AUTOPLACE, the flash chip - the nand controller on the flash chip ? both ?? b) the oobfree area is specified as a {offset, length) pair. When this gets to say the jffs2 file system what does it see. For example .oobfree = { {8, 8} } it would see 8 bytes starting at offset 8 OR 8 bytes starting at offset 0 and the mtd driver would do the mapping. more complex example .oobfree = { {3, 2}, {6, 2} } would jffs2 see 4 bytes at offset 0. or 2 sets of data at offset 3 and offset 6. I am asking because if I have a flash device that does not map per the standard includes do I have to touch jffs2 to get things to work. regards, Philip ____________________________________________________________________________________ Now that's room service! Choose from over 150,000 hotels in 45,000 destinations on Yahoo! Travel to find your fit. http://farechase.yahoo.com/promo-generic-14795097