From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ew0-f223.google.com ([209.85.219.223]) by bombadil.infradead.org with esmtp (Exim 4.69 #1 (Red Hat Linux)) id 1NMkdJ-0001k8-HL for linux-mtd@lists.infradead.org; Mon, 21 Dec 2009 15:57:22 +0000 Received: by ewy23 with SMTP id 23so4504451ewy.4 for ; Mon, 21 Dec 2009 07:57:14 -0800 (PST) MIME-Version: 1.0 Date: Mon, 21 Dec 2009 10:57:14 -0500 Message-ID: Subject: confusion UBI overhead and volume size calculations From: twebb To: linux-mtd@lists.infradead.org Content-Type: text/plain; charset=ISO-8859-1 List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , I'm very confused about the calculations for determining max-leb-cnt argument for mkfs.ubifs and vol_size for ubinize cfg file. I have a 4GiB MLC nand device that has a 64M reserved area from 0x0-0x04000000. The rest, 0x04000000-0x100000000 (4032M), is dedicated to a single MTD partition. A single UBI device will attach to the single MTD partition and have 4 volumes. I'm using mkfs.ubifs and ubinize at build time to create a single UBI image to be flashed to the MTD device. The four volumes are... vol1 = 352M vol2 = 352M vol3 = 352M vol4 = 2976M The device data sheet specifies that the minimum valid block count is 7992 (of 8192 possible), so it seems like I should reserve 200 blocks (100M) to allow for this. My questions are: 1. How does the 100M reserved for "potentially bad blocks" get handled when calculating the vol_size for each volume in the .cfg file? I'd like to leave vol1-3 intact and only take space from vol4. Would the vol_sizes be as follows? vol1 vol_size = 352M vol2 vol_size = 352M vol3 vol_size = 352M vol4 vol_size = 2976M-100M = 2876M 2. How is the overhead calculation from the linux-mtd site used in determining the vol_sizes? ("The UBI overhead is (B + 4) * SP + O * (P - B - 4) i.e., this amount of bytes will not be accessible for users.") 3. Is max-leb-cnt simple the vol_size/LEB_size? I'm really lost on this. I'd appreciate any input anyone may have on this. Thanks, twebb