From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754804AbbJ0Ryx (ORCPT ); Tue, 27 Oct 2015 13:54:53 -0400 Received: from mail-pa0-f46.google.com ([209.85.220.46]:36353 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754786AbbJ0Ryt (ORCPT ); Tue, 27 Oct 2015 13:54:49 -0400 Date: Tue, 27 Oct 2015 10:54:46 -0700 From: Brian Norris To: Boris Brezillon Cc: linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org, Ezequiel Garcia , Marek Vasut , Scott Wood , Josh Wu , Robert Jarzmik , Kyungmin Park , Han Xu , Huang Shijie Subject: Re: [PATCH 1/5] mtd: ofpart: grab device tree node directly from master device node Message-ID: <20151027175446.GT13239@google.com> References: <1445913070-17950-1-git-send-email-computersforpeace@gmail.com> <1445913070-17950-2-git-send-email-computersforpeace@gmail.com> <20151027084200.2434180f@bbrezillon> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151027084200.2434180f@bbrezillon> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Boris, On Tue, Oct 27, 2015 at 08:42:00AM +0100, Boris Brezillon wrote: > On Mon, 26 Oct 2015 19:31:06 -0700 > Brian Norris wrote: > > > It seems more logical to use a device node directly associated with the > > MTD master device (i.e., mtd->dev.of_node field) rather than requiring > > auxiliary partition parser information to be passed in by the driver in > > a separate struct. > > > > This patch supports the mtd->dev.of_node field, deprecates the parser > > data 'of_node' field, and begins using the new convention for nand_base. > > Other NAND driver conversions may now follow. > > > > Additional side benefit to assigning mtd->dev.of_node rather than using > > parser data: the driver core will automatically create a device -> node > > symlink for us. > > I like the idea, but how about pushing the solution even further and > killing the ->flash_node field which AFAICT is rendered useless by > your patch? I suppose we could do that. I do think there's something to be said for layering, though. Historically, we haven't done a very good job of layering in MTD, so low-level drivers often have to poke around in the MTD structures, even if they really should only have to know a few things about their helper subsystem/library, like NAND or SPI NOR. So with that in mind, I think the ->flash_node serves some purpose -- drivers can just initialize struct nand_chip/spi_nor and be assured that the NAND/SPI-NOR subsystems will take care of things. Now, I don't think there's much reason to suspect that we'd have a more complex mapping than 1:1 between struct mtd_info and struct nand_chip or struct spi_nor, so maybe we don't actually need duplicate storage (mtd.dev.of_node and {spi_nor,nand_chip}.flash_node), and the layering is just have these APIs: nand_set_flash_node() spi_nor_set_flash_node() which just call mtd_set_of_node()? Speaking of layering: why do we have NAND drivers initializing mtd->priv for us, yet nand_base just assumes that it points to a struct nand_chip? And why isn't struct mtd_info just embedded in struct nand_chip? Are there ever cases we want more than one (master) MTD per nand_chip? Or vice versa? Thanks for the review, Brian