Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756312Ab1DGSG6 (ORCPT ); Thu, 7 Apr 2011 14:06:58 -0400 Received: from mail-iy0-f174.google.com ([209.85.210.174]:54328 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754731Ab1DGSGz (ORCPT ); Thu, 7 Apr 2011 14:06:55 -0400 Date: Thu, 7 Apr 2011 11:06:50 -0700 From: Grant Likely To: Samuel Ortiz Cc: Felipe Balbi , Greg KH , Andres Salomon , linux-kernel@vger.kernel.org, Mark Brown , khali@linux-fr.org, ben-linux@fluff.org, Peter Korsgaard , Mauro Carvalho Chehab , David Brownell , linux-i2c@vger.kernel.org, linux-media@vger.kernel.org, netdev@vger.kernel.org, spi-devel-general@lists.sourceforge.net, Mocean Laboratories Subject: Re: [PATCH 07/19] timberdale: mfd_cell is now implicitly available to drivers Message-ID: <20110407180650.GA3261@angua.secretlab.ca> References: <20110405030428.GB29522@ponder.secretlab.ca> <20110406152322.GA2757@sortiz-mobl> <20110406155805.GA20095@suse.de> <20110406170537.GB2757@sortiz-mobl> <20110406175647.GA8048@suse.de> <20110406184733.GD2757@sortiz-mobl> <20110406185902.GN25654@legolas.emea.dhcp.ti.com> <20110407133717.GA3923@sortiz-mobl> <20110407143515.GC26452@angua.secretlab.ca> <20110407150322.GB3923@sortiz-mobl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110407150322.GB3923@sortiz-mobl> 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 Content-Length: 6657 Lines: 160 On Thu, Apr 07, 2011 at 05:03:23PM +0200, Samuel Ortiz wrote: > On Thu, Apr 07, 2011 at 07:35:15AM -0700, Grant Likely wrote: > > > Below is a patch for the Xilinx SPI example. Although this would fix the > > > issue, we'd still have to do that on device per device basis. I had a similar > > > solution where MFD drivers would set a flag for sub drivers that don't need > > > any of the MFD bits. In that case the MFD core code would just forward the > > > platform data, instead of embedding it through an MFD cell. > > > > platform_data is already a fiddly bit where you don't know what > > structure type platform_data points at; it is implicitly known and > > easy to get wrong. This solution makes me *very* nervous > > because it would become even easier to get a mismatch on the > > platform_data pointer type. > How would that be more error prone than say a board file instantiating a > platform device after having set the platform_data pointer to point to an > implicitely know structure reference ? Yes, platform_data is already troublesome, but at least current convention is a 1:1 relationship between driver and platform_data type. I still hate it and want something better, but it is what we have. The problem with what having a different platform_data pointer depending on the instantiation means that it adds yet another level of decision that needs to be made and is very easy to get wrong. So, yes, platform_data is bad. I don't want to see it get any worse. > > Cheers, > Samuel. > > P.S.: Would you be ok with something like the patch below ? Not really because it requires the driver to make the correct decision about the platform_data type depending on the driver name. It is easy to get wrong and the compiler cannot help you catch it. I've talked with Greg, and adding the mfd_cell pointer to platform_device will be okay in the short term. In the long term I'm looking at creating a better way of attaching type-safe data to devices that will pretty much eliminate this issue. > > > > --- > > > drivers/mfd/timberdale.c | 8 ++++---- > > > drivers/spi/xilinx_spi.c | 19 ++++++++++++++++++- > > > include/linux/mfd/core.h | 3 +++ > > > 3 files changed, 25 insertions(+), 5 deletions(-) > > > > > > diff --git a/drivers/mfd/timberdale.c b/drivers/mfd/timberdale.c > > > index 94c6c8a..c9220ce 100644 > > > --- a/drivers/mfd/timberdale.c > > > +++ b/drivers/mfd/timberdale.c > > > @@ -416,7 +416,7 @@ static __devinitdata struct mfd_cell timberdale_cells_bar0_cfg0[] = { > > > .mfd_data = &timberdale_radio_platform_data, > > > }, > > > { > > > - .name = "xilinx_spi", > > > + .name = "mfd_xilinx_spi", > > > .num_resources = ARRAY_SIZE(timberdale_spi_resources), > > > .resources = timberdale_spi_resources, > > > .mfd_data = &timberdale_xspi_platform_data, > > > @@ -476,7 +476,7 @@ static __devinitdata struct mfd_cell timberdale_cells_bar0_cfg1[] = { > > > .mfd_data = &timberdale_radio_platform_data, > > > }, > > > { > > > - .name = "xilinx_spi", > > > + .name = "mfd_xilinx_spi", > > > .num_resources = ARRAY_SIZE(timberdale_spi_resources), > > > .resources = timberdale_spi_resources, > > > .mfd_data = &timberdale_xspi_platform_data, > > > @@ -526,7 +526,7 @@ static __devinitdata struct mfd_cell timberdale_cells_bar0_cfg2[] = { > > > .mfd_data = &timberdale_radio_platform_data, > > > }, > > > { > > > - .name = "xilinx_spi", > > > + .name = "mfd_xilinx_spi", > > > .num_resources = ARRAY_SIZE(timberdale_spi_resources), > > > .resources = timberdale_spi_resources, > > > .mfd_data = &timberdale_xspi_platform_data, > > > @@ -570,7 +570,7 @@ static __devinitdata struct mfd_cell timberdale_cells_bar0_cfg3[] = { > > > .mfd_data = &timberdale_radio_platform_data, > > > }, > > > { > > > - .name = "xilinx_spi", > > > + .name = "mfd_xilinx_spi", > > > .num_resources = ARRAY_SIZE(timberdale_spi_resources), > > > .resources = timberdale_spi_resources, > > > .mfd_data = &timberdale_xspi_platform_data, > > > diff --git a/drivers/spi/xilinx_spi.c b/drivers/spi/xilinx_spi.c > > > index c69c6f2..3287b84 100644 > > > --- a/drivers/spi/xilinx_spi.c > > > +++ b/drivers/spi/xilinx_spi.c > > > @@ -471,7 +471,11 @@ static int __devinit xilinx_spi_probe(struct platform_device *dev) > > > struct spi_master *master; > > > u8 i; > > > > > > - pdata = mfd_get_data(dev); > > > + if (platform_get_device_id(dev) && > > > + platform_get_device_id(dev)->driver_data & MFD_PLATFORM_DEVICE) > > > + pdata = mfd_get_data(dev); > > > + else > > > + pdata = dev->dev.platform_data; > > > if (pdata) { > > > num_cs = pdata->num_chipselect; > > > little_endian = pdata->little_endian; > > > @@ -530,6 +534,18 @@ static int __devexit xilinx_spi_remove(struct platform_device *dev) > > > /* work with hotplug and coldplug */ > > > MODULE_ALIAS("platform:" XILINX_SPI_NAME); > > > > > > +static const struct platform_device_id xilinx_spi_id_table[] = { > > > + { > > > + .name = XILINX_SPI_NAME, > > > + }, > > > + { > > > + .name = "mfd_xilinx_spi", > > > + .driver_data = MFD_PLATFORM_DEVICE, > > > + }, > > > + { }, /* Terminating Entry */ > > > +}; > > > +MODULE_DEVICE_TABLE(platform, xilinx_spi_id_table); > > > + > > > static struct platform_driver xilinx_spi_driver = { > > > .probe = xilinx_spi_probe, > > > .remove = __devexit_p(xilinx_spi_remove), > > > @@ -538,6 +554,7 @@ static struct platform_driver xilinx_spi_driver = { > > > .owner = THIS_MODULE, > > > .of_match_table = xilinx_spi_of_match, > > > }, > > > + .id_table = xilinx_spi_id_table, > > > }; > > > > > > static int __init xilinx_spi_pltfm_init(void) > > > diff --git a/include/linux/mfd/core.h b/include/linux/mfd/core.h > > > index ad1b19a..13f31f4 100644 > > > --- a/include/linux/mfd/core.h > > > +++ b/include/linux/mfd/core.h > > > @@ -89,6 +89,9 @@ static inline const struct mfd_cell *mfd_get_cell(struct platform_device *pdev) > > > return pdev->dev.platform_data; > > > } > > > > > > +/* */ > > > +#define MFD_PLATFORM_DEVICE BIT(0) > > > + > > > /* > > > * Given a platform device that's been created by mfd_add_devices(), fetch > > > * the .mfd_data entry from the mfd_cell that created it. > > > > > > > > > -- > > > Intel Open Source Technology Centre > > > http://oss.intel.com/ > > -- > Intel Open Source Technology Centre > http://oss.intel.com/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/