Re: [PATCH 07/19] timberdale: mfd_cell is now implicitly available to drivers

[Samuel Ortiz <sameo-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>]

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 ?

Cheers,
Samuel.

P.S.: Would you be ok with something like the patch below ?

> > ---
> >  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/