Re: [PATCH V7 08/11] ACPI: always register memory hotplug scan handler even if CONFIG_X86_INTEL_LPSS is cleared

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

On Monday, May 26, 2014 01:56:36 PM Mika Westerberg wrote:
> On Fri, May 23, 2014 at 02:02:30AM +0800, Zhang Rui wrote:
> > The new ACPI device enumeration mechanism, which will be introduced
> > in a later patch, will enumerate the _HID devices w/o any scan
> > handler attached to platform bus.
> > This means that, for the devices that are attached to a configurable
> > scan handler, we should make sure no platform devices would be
> > created for them even if the scan handler is compiled out.
> > 
> > Fix this problem for lpss devices by always register the lpss scan handler,
> > but with meaningful callbacks only when CONFIG_X86_INTEL_LPSS is set.
> > 
> > Signed-off-by: Zhang Rui <rui.zhang@intel.com>
> > ---
> >  drivers/acpi/Makefile    |  2 +-
> >  drivers/acpi/acpi_lpss.c | 63 ++++++++++++++++++++++++++++++------------------
> >  drivers/acpi/internal.h  |  4 ---
> >  3 files changed, 41 insertions(+), 28 deletions(-)
> > 
> > diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
> > index 171efc2..605eff7 100644
> > --- a/drivers/acpi/Makefile
> > +++ b/drivers/acpi/Makefile
> > @@ -39,7 +39,7 @@ acpi-y				+= processor_core.o
> >  acpi-y				+= ec.o
> >  acpi-$(CONFIG_ACPI_DOCK)	+= dock.o
> >  acpi-y				+= pci_root.o pci_link.o pci_irq.o
> > -acpi-$(CONFIG_X86_INTEL_LPSS)	+= acpi_lpss.o
> > +acpi-y				+= acpi_lpss.o
> >  acpi-y				+= acpi_platform.o
> >  acpi-y				+= acpi_pnp.o
> >  acpi-y				+= power.o
> > diff --git a/drivers/acpi/acpi_lpss.c b/drivers/acpi/acpi_lpss.c
> > index 69e29f4..bb5b3f2 100644
> > --- a/drivers/acpi/acpi_lpss.c
> > +++ b/drivers/acpi/acpi_lpss.c
> > @@ -24,6 +24,8 @@
> >  
> >  ACPI_MODULE_NAME("acpi_lpss");
> >  
> > +#ifdef CONFIG_X86_INTEL_LPSS
> > +
> >  #define LPSS_CLK_SIZE	0x04
> >  #define LPSS_LTR_SIZE	0x18
> >  
> > @@ -159,40 +161,50 @@ static struct lpss_device_desc byt_i2c_dev_desc = {
> >  	.shared_clock = &i2c_clock,
> >  };
> >  
> > +#define LPSS_PTR(desc) ((unsigned long)&desc)
> > +
> > +#else
> > +
> > +#define LPSS_PTR(desc) 0
> > +
> > +#endif
> > +
> >  static const struct acpi_device_id acpi_lpss_device_ids[] = {
> >  	/* Generic LPSS devices */
> > -	{ "INTL9C60", (unsigned long)&lpss_dma_desc },
> > +	{ "INTL9C60", LPSS_PTR(lpss_dma_desc) },
> >  
> >  	/* Lynxpoint LPSS devices */
> > -	{ "INT33C0", (unsigned long)&lpt_dev_desc },
> > -	{ "INT33C1", (unsigned long)&lpt_dev_desc },
> > -	{ "INT33C2", (unsigned long)&lpt_dev_desc },
> > -	{ "INT33C3", (unsigned long)&lpt_dev_desc },
> > -	{ "INT33C4", (unsigned long)&lpt_uart_dev_desc },
> > -	{ "INT33C5", (unsigned long)&lpt_uart_dev_desc },
> > -	{ "INT33C6", (unsigned long)&lpt_sdio_dev_desc },
> > +	{ "INT33C0", LPSS_PTR(lpt_dev_desc) },
> > +	{ "INT33C1", LPSS_PTR(lpt_dev_desc) },
> > +	{ "INT33C2", LPSS_PTR(lpt_dev_desc) },
> > +	{ "INT33C3", LPSS_PTR(lpt_dev_desc) },
> > +	{ "INT33C4", LPSS_PTR(lpt_uart_dev_desc) },
> > +	{ "INT33C5", LPSS_PTR(lpt_uart_dev_desc) },
> > +	{ "INT33C6", LPSS_PTR(lpt_sdio_dev_desc) },
> >  	{ "INT33C7", },
> >  
> >  	/* BayTrail LPSS devices */
> > -	{ "80860F09", (unsigned long)&byt_pwm_dev_desc },
> > -	{ "80860F0A", (unsigned long)&byt_uart_dev_desc },
> > -	{ "80860F0E", (unsigned long)&byt_spi_dev_desc },
> > -	{ "80860F14", (unsigned long)&byt_sdio_dev_desc },
> > -	{ "80860F41", (unsigned long)&byt_i2c_dev_desc },
> > +	{ "80860F09", LPSS_PTR(byt_pwm_dev_desc) },
> > +	{ "80860F0A", LPSS_PTR(byt_uart_dev_desc) },
> > +	{ "80860F0E", LPSS_PTR(byt_spi_dev_desc) },
> > +	{ "80860F14", LPSS_PTR(byt_sdio_dev_desc) },
> > +	{ "80860F41", LPSS_PTR(byt_i2c_dev_desc) },
> >  	{ "INT33B2", },
> >  
> > -	{ "INT3430", (unsigned long)&lpt_dev_desc },
> > -	{ "INT3431", (unsigned long)&lpt_dev_desc },
> > -	{ "INT3432", (unsigned long)&lpt_dev_desc },
> > -	{ "INT3433", (unsigned long)&lpt_dev_desc },
> > -	{ "INT3434", (unsigned long)&lpt_uart_dev_desc },
> > -	{ "INT3435", (unsigned long)&lpt_uart_dev_desc },
> > -	{ "INT3436", (unsigned long)&lpt_sdio_dev_desc },
> > +	{ "INT3430", LPSS_PTR(lpt_dev_desc) },
> > +	{ "INT3431", LPSS_PTR(lpt_dev_desc) },
> > +	{ "INT3432", LPSS_PTR(lpt_dev_desc) },
> > +	{ "INT3433", LPSS_PTR(lpt_dev_desc) },
> > +	{ "INT3434", LPSS_PTR(lpt_uart_dev_desc) },
> > +	{ "INT3435", LPSS_PTR(lpt_uart_dev_desc) },
> > +	{ "INT3436", LPSS_PTR(lpt_sdio_dev_desc) },
> >  	{ "INT3437", },
> >  
> >  	{ }
> >  };
> >  
> > +#ifdef CONFIG_X86_INTEL_LPSS
> > +
> >  static int is_memory(struct acpi_resource *res, void *not_used)
> >  {
> >  	struct resource r;
> > @@ -503,18 +515,23 @@ static void acpi_lpss_unbind(struct device *dev)
> >  {
> >  	dev->power.set_latency_tolerance = NULL;
> >  }
> > +#endif /* CONFIG_X86_INTEL_LPSS */
> >  
> >  static struct acpi_scan_handler lpss_handler = {
> >  	.ids = acpi_lpss_device_ids,
> > -	.attach = acpi_lpss_create_device,
> > -	.bind = acpi_lpss_bind,
> > -	.unbind = acpi_lpss_unbind,
> >  };
> >  
> >  void __init acpi_lpss_init(void)
> >  {
> > +#ifdef CONFIG_X86_INTEL_LPSS
> >  	if (!lpt_clk_init()) {
> >  		bus_register_notifier(&platform_bus_type, &acpi_lpss_nb);
> > +		lpss_handler.attach = acpi_lpss_create_device;
> > +		lpss_handler.bind = acpi_lpss_bind;
> > +		lpss_handler.unbind = acpi_lpss_unbind;
> >  		acpi_scan_add_handler(&lpss_handler);
> > +		return;
> >  	}
> > +#endif
> > +	acpi_scan_add_handler(&lpss_handler);
> 
> I'm wondering whether it is worth the ugliness to get platform bus
> enumeration the default?
> 
> Since you already have the PNP whitelist, can't we just use that for PNP
> and keep these files as they are? In other words, don't make any kind of
> physical device by default and let the scan handlers to decide.

Well, that's tempting, but then we'd get one more whitelist pretty much without
any benefit, because we'd be still going to have the list in acpi_platform.c.

The purpose of the whole exercise is not to prevent PNP devices from being
created by default (which admittedly is a nice side effect), but to get rid
of the white list in acpi_platform.c - and in particular, to avoid the
necessity to add every ACPI-enumerated platform device to that list in the
future.

Rafael