From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.gmx.net ([213.165.64.20]) by bombadil.infradead.org with smtp (Exim 4.68 #1 (Red Hat Linux)) id 1KYSwF-00037N-Np for linux-mtd@lists.infradead.org; Wed, 27 Aug 2008 21:52:28 +0000 Message-ID: <48B5CC98.9000904@gmx.net> Date: Wed, 27 Aug 2008 23:52:24 +0200 From: Carl-Daniel Hailfinger MIME-Version: 1.0 To: Jamie Lokier Subject: Re: [PATCH 2/2] Add support for > 2GiB MTD devices References: <1219815617.18027.132.camel@sauron> <20080827185142.GE27491@shareable.org> In-Reply-To: <20080827185142.GE27491@shareable.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: linux-mtd-bounces@lists.infradead.org, linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org, Bruce_Leonard@selinc.com, Bruce Leonard List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 27.08.2008 20:51, Jamie Lokier wrote: > Bruce_Leonard@selinc.com wrote: > >> I'm still reluctant to change size to a 64-bit value. There's a vague >> recolection of early conversations on the list that there would be little >> acceptance for that. And that probably has to do with the ongoing >> conversation about ABI changes. What I could do to eliminate the >> multiplication is introduce the same concept that the NAND layer uses, >> shift values. After all, erasesize should always be a power of 2, making >> that a power of 2 multiplication which can be done via shifts. By >> changing erasesize to erasesize_shift, I'd get something like this: >> >> return a->num_eraseblocks == 0 ? a->size : a->num_eraseblocks << >> a->erasesize_shift >> >> How would that suit you? >> > > Are you sure it's always going to be a power of 2? > > What if someone targets a board with 3 chips wired to shared address > and parallel data buses? > > Or if someone makes a weird chip? Or if you can format it in > different ways according to desired ECC level (like you can with CDs)? > IIRC I saw a datasheet for such a chip (selectable erasesize with non-power-of-2 default) some weeks ago and it had entered production a few months ago. The erasesize was alwas a multiple of 16, though. Sorry for not remembering more details. Regards, Carl-Daniel -- http://www.hailfinger.org/