From mboxrd@z Thu Jan 1 00:00:00 1970 From: Grant Likely Subject: Re: [PATCH 07/19] timberdale: mfd_cell is now implicitly available to drivers Date: Thu, 7 Apr 2011 07:35:15 -0700 Message-ID: <20110407143515.GC26452@angua.secretlab.ca> References: <20110404100314.GC2751@sortiz-mobl> <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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii 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 To: Samuel Ortiz Return-path: Content-Disposition: inline In-Reply-To: <20110407133717.GA3923@sortiz-mobl> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-spi.vger.kernel.org On Thu, Apr 07, 2011 at 03:40:23PM +0200, Samuel Ortiz wrote: > Hi Felipe, > > On Wed, Apr 06, 2011 at 09:59:02PM +0300, Felipe Balbi wrote: > > Hi, > > > > On Wed, Apr 06, 2011 at 08:47:34PM +0200, Samuel Ortiz wrote: > > > > > > What is a "MFD cell pointer" and why is it needed in struct device? > > > > > An MFD cell is an MFD instantiated device. > > > > > MFD (Multi Function Device) drivers instantiate platform devices. Those > > > > > devices drivers sometimes need a platform data pointer, sometimes an MFD > > > > > specific pointer, and sometimes both. Also, some of those drivers have been > > > > > implemented as MFD sub drivers, while others know nothing about MFD and just > > > > > expect a plain platform_data pointer. > > > > > > > > That sounds like a bug in those drivers, why not fix them to properly > > > > pass in the correct pointer? > > > Because they're drivers for generic IPs, not MFD ones. By forcing them to use > > > MFD specific structure and APIs, we make it more difficult for platform code > > > to instantiate them. > > > > I agree. What I do on those cases is to have a simple platform_device > > for the core IP driver and use platform_device_id tables to do runtime > > checks of the small differences. If one platform X doesn't use a > > platform_bus, it uses e.g. PCI, then you make a PCI "bridge" which > > allocates a platform_device with the correct name and adds that to the > > driver model. > I see, thanks. > 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. g. > > Cheers, > Samuel. > > --- > 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/