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Date: Thu, 7 Apr 2011 07:35:15 -0700
From: Grant Likely <grant.likely@...retlab.ca>
To: Samuel Ortiz <sameo@...ux.intel.com>
Cc: Felipe Balbi <balbi@...com>, Greg KH <gregkh@...e.de>,
Andres Salomon <dilinger@...ued.net>,
linux-kernel@...r.kernel.org,
Mark Brown <broonie@...nsource.wolfsonmicro.com>,
khali@...ux-fr.org, ben-linux@...ff.org,
Peter Korsgaard <jacmet@...site.dk>,
Mauro Carvalho Chehab <mchehab@...radead.org>,
David Brownell <dbrownell@...rs.sourceforge.net>,
linux-i2c@...r.kernel.org, linux-media@...r.kernel.org,
netdev@...r.kernel.org, spi-devel-general@...ts.sourceforge.net,
Mocean Laboratories <info@...ean-labs.com>
Subject: Re: [PATCH 07/19] timberdale: mfd_cell is now implicitly available
to drivers
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/
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