From mboxrd@z Thu Jan 1 00:00:00 1970 From: Feng Tang Subject: Re: [PATCH] spi: add a bits_per_word to struct spi_board_info Date: Thu, 9 Sep 2010 11:14:45 +0800 Message-ID: <20100909111445.47145de9@feng-i7> References: <20100902100128.5d5b7d87@feng-i7> <930634.1250.qm@web180310.mail.gq1.yahoo.com> <20100902141348.669aa817@feng-i7> <20100908202159.GG7065@angua.secretlab.ca> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: David Brownell , "spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org" To: Grant Likely Return-path: In-Reply-To: <20100908202159.GG7065-MrY2KI0G/OVr83L8+7iqerDks+cytr/Z@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: spi-devel-general-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: linux-spi.vger.kernel.org Hi Grant, On Thu, 9 Sep 2010 04:21:59 +0800 Grant Likely wrote: > > > > > > Yes, driver itself > > > > know the bits_per_word info best in most case, but there > > > > is > > > > some device (Option GTM501L spi modem) which supports > > > > multiple > > > > bits_per_mode option, and here platform code > > > is the good place to set it. > > > > > > > > > Not unless it knows which mode the driver uses... > > > a kind of layering violation. > > > > spi_board_info has a member of "mode", so for my platform, I prefer > > to set all these infos in platform code, while protocol driver can > > check if the preset infos like speed_hz/mode/bits_per_word are > > supported. > > The real problem is that spi_drivers are normally allowed to change > bits_per_word as needed. For drivers who don't accept bits_per_word comes from platform code, it could just ignores it and set the value it wants. > If the spi_driver gets unbound and > rebound, then the original platform-set value for bits_per_word is > lost and the behaviour changes. Um, if you are talking about driver load/unload, then the bits_per_word info won't get lost as it is set to spi_device from spi_board_info when spi_new_device get called. > If you really want to give the driver > hints about the best setting for bits_per_word or similar, then you > should probably use a driver-specific pdata structure. Good point, really a solution to the GTM501L modem driver. But still, adding the bits_per_word to spi_board_info will be more generic when more devices which support multiple bits models show up. Thanks, Feng ------------------------------------------------------------------------------ This SF.net Dev2Dev email is sponsored by: Show off your parallel programming skills. Enter the Intel(R) Threading Challenge 2010. http://p.sf.net/sfu/intel-thread-sfd