From mboxrd@z Thu Jan 1 00:00:00 1970 From: Adrian Hunter Subject: Re: [PATCH V3 1/5] mmc: Add erase, secure erase, trim and secure trim operations Date: Thu, 01 Jul 2010 13:49:32 +0300 Message-ID: <4C2C72BC.1050207@nokia.com> References: <20100624084351.25444.30143.sendpatchset@ahunter-work.research.nokia.com> <20100624084400.25444.57158.sendpatchset@ahunter-work.research.nokia.com> <20100630152144.3822fe6b.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from smtp.nokia.com ([192.100.122.233]:62185 "EHLO mgw-mx06.nokia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752548Ab0GAKu3 (ORCPT ); Thu, 1 Jul 2010 06:50:29 -0400 In-Reply-To: <20100630152144.3822fe6b.akpm@linux-foundation.org> Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Andrew Morton Cc: linux-kernel Mailing List , Kyungmin Park , Madhusudhan Chikkature , linux-mmc Mailing List , Christoph Hellwig , Jens Axboe Andrew Morton wrote: > On Thu, 24 Jun 2010 11:44:00 +0300 > Adrian Hunter wrote: > >> SD/MMC cards tend to support an erase operation. In addition, >> eMMC v4.4 cards can support secure erase, trim and secure trim >> operations that are all variants of the basic erase command. > > The patch proposes a new userspace interface via sysfs, yes? , Just two read-only values > > Please fully describe that interface and its operation in the > changelog. It'd also be nice to add permanent documentation for it. > OK >>>From reading the code, it appears that erase_size and > preferred_erase_size have units in bytes. But users shouldn't need to > read the code to find that out. What are the alignemnt and size > requirements on these? What is their position in /sys? What do they > actually *do* and what is the difference between them? > > etetera. People want to review this code and other people actually > want to use it. I'm not sure that I want to try to review this code > when nobody's told me what interface it implements and how it's > supposed to work. Seems that whoever implemented BLKDISCARD didn't > want anyone to use it either. Sigh. > > > All of mmc core appears to use 32-bit quantities to represent sectors, > yes? Why didn't it use sector_t? What are the implications of this? SD/MMC addressing uses 32-bit values. There is a known 2TB limit for SD/MMC cards. As cards are only just getting to 64GB, that limit is some way off, and it is not clear NAND technology can get there in a SD/MMC package anyway. I don't know why sector_t is not used. I guess it would complicate doing division since it can be 64-bit. The implications are minimal. In the unlikely event SD/MMC cards ever exceed 2TB some changes will be needed, but the standard would have to change to allow that first.