From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailserv.intranet.gr ([146.124.14.106]) by pentafluge.infradead.org with esmtp (Exim 4.14 #3 (Red Hat Linux)) id 19Q1DJ-000249-Ap for ; Wed, 11 Jun 2003 09:44:14 +0100 Received: from mailserv.intranet.gr (localhost [127.0.0.1]) by mailserv.intranet.gr (8.11.7/8.11.3) with ESMTP id h5B8l0D29132 for ; Wed, 11 Jun 2003 11:47:00 +0300 (EEST) Received: from ifaistos.intranet.gr (ifaistos.intranet.GR [146.124.20.203]) by mailserv.intranet.gr (8.11.7/8.11.3) with ESMTP id h5B8kxY29117 for ; Wed, 11 Jun 2003 11:46:59 +0300 (EEST) Received: from intracom.gr (pcrnd46 [146.124.20.92]) by ifaistos.intranet.gr (8.9.1b+Sun/8.9.1) with ESMTP id LAA29907 for ; Wed, 11 Jun 2003 11:40:41 +0300 (EET DST) Message-ID: <3EE6EBA0.3080508@intracom.gr> Date: Wed, 11 Jun 2003 11:43:12 +0300 From: Pantelis Antoniou MIME-Version: 1.0 To: linux-mtd@lists.infradead.org Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Cram FS on NAND - How to do this? List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi As it currently stands the only filesystems supporting raw NAND flash are: JFFS2: Read/write, compressed, best support, slow startup. YAFFS: Read/write, not compressed, newcomer, fast startup. I have a requirement to have a compressed read only root filesystem in my board and I've come to the conclussion that the best fit would be CRAMFS if only had any concept of bad blocks. Looking at the code for CRAMFS I see that it would not be very difficult to hack it to detect the bad blocks and skip over them on startup. We could rely on the same OOB info that JFFS2 has, and just make a mapping list as follows: NAND block bad? fs block ---------- ---- -------- 0 n 0 1 n 1 2 y skip 3 n 2 ... etc The first complication is that CRAMFS works with PAGE_SIZE blocks only, and that should be taken into account. The second is that this is the first time I hack filesystem code and I would like to ask the list if you see any difficulties ahead. What are your thoughts in this? Regards Pantelis