Re: [PATCH 1/4] ACPI / scan: Introduce struct acpi_scan_handler

[Toshi Kani <toshi.kani@hp.com>]

On Tue, 2013-01-29 at 12:28 +0100, Rafael J. Wysocki wrote:
> On Monday, January 28, 2013 07:35:39 PM Toshi Kani wrote:
> > On Mon, 2013-01-28 at 13:59 +0100, Rafael J. Wysocki wrote:
> > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > > 
> > > Introduce struct acpi_scan_handler for representing objects that
> > > will do configuration tasks depending on ACPI device nodes'
> > > hardware IDs (HIDs).
> > > 
> > > Currently, those tasks are done either directly by the ACPI namespace
> > > scanning code or by ACPI device drivers designed specifically for
> > > this purpose.  None of the above is desirable, however, because
> > > doing that directly in the namespace scanning code makes that code
> > > overly complicated and difficult to follow and doing that in
> > > "special" device drivers leads to a great deal of confusion about
> > > their role and to confusing interactions with the driver core (for
> > > example, sysfs directories are created for those drivers, but they
> > > are completely unnecessary and only increase the kernel's memory
> > > footprint in vain).
> > > 
> > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > > ---
> > >  Documentation/acpi/scan_handlers.txt |   77 +++++++++++++++++++++++++++++++++++
> > >  drivers/acpi/scan.c                  |   60 ++++++++++++++++++++++++---
> > >  include/acpi/acpi_bus.h              |   14 ++++++
> > >  3 files changed, 144 insertions(+), 7 deletions(-)
> > > 
> > > Index: test/include/acpi/acpi_bus.h
> > > ===================================================================
> > > --- test.orig/include/acpi/acpi_bus.h
> > > +++ test/include/acpi/acpi_bus.h
> > > @@ -84,6 +84,18 @@ struct acpi_driver;
> > >  struct acpi_device;
> > >  
> > >  /*
> > > + * ACPI Scan Handler
> > > + * -----------------
> > > + */
> > > +
> > > +struct acpi_scan_handler {
> > > +	const struct acpi_device_id *ids;
> > > +	struct list_head list_node;
> > > +	int (*attach)(struct acpi_device *dev, const struct acpi_device_id *id);
> > > +	void (*detach)(struct acpi_device *dev);
> > > +};
> > > +
> > > +/*
> > >   * ACPI Driver
> > >   * -----------
> > >   */
> > > @@ -269,6 +281,7 @@ struct acpi_device {
> > >  	struct acpi_device_wakeup wakeup;
> > >  	struct acpi_device_perf performance;
> > >  	struct acpi_device_dir dir;
> > > +	struct acpi_scan_handler *handler;
> > >  	struct acpi_driver *driver;
> > >  	void *driver_data;
> > >  	struct device dev;
> > > @@ -382,6 +395,7 @@ int acpi_bus_receive_event(struct acpi_b
> > >  static inline int acpi_bus_generate_proc_event(struct acpi_device *device, u8 type, int data)
> > >  	{ return 0; }
> > >  #endif
> > > +int acpi_scan_add_handler(struct acpi_scan_handler *handler);
> > >  int acpi_bus_register_driver(struct acpi_driver *driver);
> > >  void acpi_bus_unregister_driver(struct acpi_driver *driver);
> > >  int acpi_bus_scan(acpi_handle handle);
> > > Index: test/drivers/acpi/scan.c
> > > ===================================================================
> > > --- test.orig/drivers/acpi/scan.c
> > > +++ test/drivers/acpi/scan.c
> > > @@ -53,6 +53,7 @@ static const struct acpi_device_id acpi_
> > >  static LIST_HEAD(acpi_device_list);
> > >  static LIST_HEAD(acpi_bus_id_list);
> > >  static DEFINE_MUTEX(acpi_scan_lock);
> > > +static LIST_HEAD(acpi_scan_handlers_list);
> > >  DEFINE_MUTEX(acpi_device_lock);
> > >  LIST_HEAD(acpi_wakeup_device_list);
> > >  
> > > @@ -62,6 +63,15 @@ struct acpi_device_bus_id{
> > >  	struct list_head node;
> > >  };
> > >  
> > > +int acpi_scan_add_handler(struct acpi_scan_handler *handler)
> > > +{
> > > +	if (!handler || !handler->attach)
> > > +		return -EINVAL;
> > > +
> > > +	list_add_tail(&handler->list_node, &acpi_scan_handlers_list);
> > > +	return 0;
> > > +}
> > > +
> > >  /*
> > >   * Creates hid/cid(s) string needed for modalias and uevent
> > >   * e.g. on a device with hid:IBM0001 and cid:ACPI0001 you get:
> > > @@ -1570,20 +1580,42 @@ static acpi_status acpi_bus_check_add(ac
> > >  	return AE_OK;
> > >  }
> > >  
> > > +static int acpi_scan_attach_handler(struct acpi_device *device)
> > > +{
> > > +	struct acpi_scan_handler *handler;
> > > +	int ret = 0;
> > > +
> > > +	list_for_each_entry(handler, &acpi_scan_handlers_list, list_node) {
> > > +		const struct acpi_device_id *id;
> > > +
> > > +		id = __acpi_match_device(device, handler->ids);
> > > +		if (!id)
> > > +			continue;
> > > +
> > > +		ret = handler->attach(device, id);
> > > +		if (ret > 0) {
> > > +			device->handler = handler;
> > > +			break;
> > > +		} else if (ret < 0) {
> > > +			break;
> > > +		}
> > > +	}
> > > +	return ret;
> > > +}
> > 
> > Now that we have full control over the attach logic, it would be great
> > if we can update it to match with the ACPI spec -- HID has priority over
> > CIDs, and CIDs are also listed in their priority.  For example, Device-X
> > has HID and CID.  In this case, this Device-X should be attached to
> > Handler-A since it supports HID.  The current logic simply chooses a
> > handler whichever registered before.  
> > 
> > Device-X: HID PNPID-A, CID PNPID-B
> > Handler-A: PNPID-A
> > Handler-B: PNPID-B
> > 
> > So, the attach logic should be something like:
> > 
> > list_for_each_entry(hwid, acpi_device->pnp.ids,) {
> > 	list_for_each_entry(,&acpi_scan_handlers_list,)
> > 		check if this handler supports a given hwid
> > }
> 
> OK, I see the problem, but I think it's better to address it in a separate
> patch on top of the current series.

I agree.

> I'm not sure what approach is best, though.  Do you think there should be two
> passes the first of which will check HIDs only and the second one will check
> CIDs?  Or do you have something different in mind?

HID and CIDs are already listed in their priority order in
acpi_device->pnp.ids.  So, the single pass like I described above should
work.

Thanks,
-Toshi