From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-bl2lp0212.outbound.protection.outlook.com ([207.46.163.212] helo=na01-bl2-obe.outbound.protection.outlook.com) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1WegYA-0002o0-PB for linux-mtd@lists.infradead.org; Mon, 28 Apr 2014 08:04:32 +0000 Date: Mon, 28 Apr 2014 15:06:08 +0800 From: Huang Shijie To: Marek Vasut Subject: Re: [PATCH V3] Add support for flag status register on Micron chips. Message-ID: <20140428070602.GA29525@localhost> References: <1398175396-7560-1-git-send-email-grmoore@altera.com> <201404260012.24311.marex@denx.de> <20140426031011.GA4811@localhost.localdomain> <201404280706.18068.marex@denx.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <201404280706.18068.marex@denx.de> Cc: ggrahammoore@gmail.com, Insop Song , Graham Moore , Sascha Hauer , Jingoo Han , Geert Uytterhoeven , linux-kernel@vger.kernel.org, Yves Vandervennet , linux-mtd@lists.infradead.org, Artem Bityutskiy , Alan Tull , Sourav Poddar , Brian Norris , Huang Shijie , David Woodhouse , Dinh Nguyen List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, Apr 28, 2014 at 07:06:17AM +0200, Marek Vasut wrote: > On Saturday, April 26, 2014 at 05:10:13 AM, Huang Shijie wrote: > > On Sat, Apr 26, 2014 at 12:12:24AM +0200, Marek Vasut wrote: > > > > > > the drivers may fills this hook itself, so the code should like this: > > > > > > -------------------------------------------------- > > > > > > > > > > > > if ((info->flags & USE_FSR) && > > > > > > > > > > > > nor->wait_till_ready == spi_nor_wait_till_fsr_ready) > > > > > > > > > > > > nor->wait_till_ready = spi_nor_wait_till_fsr_ready; > > > > > > > > > > > > -------------------------------------------------- > > > > > > > > > > I sense a misdesign of the SPI NOR subsystem here. The subsystem and > > > > > the driver compete for a function pointer here ? I guess one should > > > > > have precedence in some way then ... and also, they should be two > > > > > different pointers, where the subsystem decides which to use. > > > > > > > > the subsystem do not decides which one to use, the driver decides which > > > > one to use. > > > > > > > > If driver has its own @wait_till_ready , it means the driver knows the > > > > feature, and has implemented it in its own @wait_till_ready. > > > > > > > > If the driver does not fill any wait_till_ready, it means the driver > > > > will use the default @wait_till_ready. We can treat the > > > > spi_nor_wait_till_fsr_ready as a default hook too. > > > > > > I see the driver overwriting a hook previously set by the subsystem. This > > > > not sure ;) > > > > The driver set the hooks before the subsystem set these hooks. > > > > If the driver has already set the @wait_till_ready hook before it calls > > the spi_nor_scan, the subsystem will not set the hook anymore. > > > > Please see the spi_nor_check(). > > Two things competing over the same pointer looks misdesigned to me. I will need > to dig into this one more time ... Please refer to the code for NAND chip, the nand_get_flash_type() : ----------------------------------------------------------- /* Do not replace user supplied command function! */ if (mtd->writesize > 512 && chip->cmdfunc == nand_command) chip->cmdfunc = nand_command_lp; ----------------------------------------------------------- It uses the same logic: " Do not replace user supplied command function!" thanks Huang Shijie