Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755139AbcJMMSm (ORCPT ); Thu, 13 Oct 2016 08:18:42 -0400 Received: from devils.ext.ti.com ([198.47.26.153]:46723 "EHLO devils.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752041AbcJMMSc (ORCPT ); Thu, 13 Oct 2016 08:18:32 -0400 From: Vignesh R Subject: Re: [PATCH RESEND] ARM: dts: keystone-k2*: Increase SPI Flash partition size for U-Boot To: Russell King - ARM Linux References: <20161010141141.21333-1-vigneshr@ti.com> <20161010143144.GB1041@n2100.armlinux.org.uk> <20161012115703.GE1041@n2100.armlinux.org.uk> CC: Santosh Shilimkar , "devicetree@vger.kernel.org" , Rob Herring , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "Karicheri, Muralidharan" Message-ID: Date: Thu, 13 Oct 2016 17:46:53 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 In-Reply-To: <20161012115703.GE1041@n2100.armlinux.org.uk> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2111 Lines: 58 On Wednesday 12 October 2016 05:27 PM, Russell King - ARM Linux wrote: > On Wed, Oct 12, 2016 at 04:30:28PM +0530, Vignesh R wrote: [...] >>> >>> - What is this "misc" partition? >>> >> >> This partition seems to exists from the very beginning. I believe, this >> is just a spare area of flash that can be used as per end-user >> requirement. Either to store a small filesystem or kernel. Copying >> Murali who added above partition if he has any input here. >> >>> - Why is it safe to move the "misc" partition in this way? >>> >>> - Do users need to do anything with data stored in the "misc" partition >>> when changing kernels? >>> >> >> MTD layer will take care of most abstractions (like start address etc). >> Will add a note in commit message informing about the reduction in size >> of the partition. >> >>> If the "misc" partition is simply unused space on the flash device, why >>> list it in DT? >>> >> >> If the unused space is not listed in the DT, then there is no /dev/mtdX >> node created for the unused section. User will then have to manually >> edit DT, in order to get the node and mount it. Instead, lets make it >> available by default. > > So, taken all together, your argument is: > > - We want a user partition > - It's okay to destroy the data in the user's partition by moving it > around randomly between kernel versions. > > The two do not naturally go together at all. You're messing with user > expectations in ways you should not be. This really is not an acceptable > approach. > Ok, I understand that if the user just updates to new kernel(w/o updating bootloader) then this patch will end up setting "misc" partition at wrong offset. At this point, I don't see how to provide a way to upgrade boot loader at the same time support old and new layouts simultaneously. Could you please suggest an alternative approach that would enable users to update U-Boot partition? If not, then I guess, will have to drop this patch. Note that, this means there won't be a straight forward way of updating SPI U-Boot partition from kernel for K2 devices. -- Regards Vignesh