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Date: Thu, 23 Oct 2014 01:21:06 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc: Arnd Bergmann <arnd@...db.de>,
Alexandre Courbot <gnurou@...il.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Grant Likely <grant.likely@...aro.org>,
ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
Aaron Lu <aaron.lu@...el.com>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
Linus Walleij <linus.walleij@...aro.org>,
Dmitry Torokhov <dmitry.torokhov@...il.com>,
Bryan Wu <cooloney@...il.com>,
Darren Hart <dvhart@...ux.intel.com>,
Mark Rutland <mark.rutland@....com>
Subject: Re: GPIO bindings guidelines (Was: Re: [PATCH v5 10/12] gpio: Support for unified device properties interface)
On Wednesday, October 22, 2014 05:56:51 PM Mika Westerberg wrote:
> On Wed, Oct 22, 2014 at 04:07:08PM +0200, Rafael J. Wysocki wrote:
> > Moreover, we need to clarify what situation we're really talking about.
> >
> > For one, drivers using the unified interface only will always use names for
> > GPIOs, because they have to assume that either a DT or ACPI w/ _DSD is present.
> > This is the cost of keeping those drivers firmware interface agnostic.
> >
> > So it looks like we're not talking about this case here.
>
> We are talking about the case of rfkill-gpio.c where it definitely wants
> to use properties for the GPIOs but it cannot be sure if the underlying
> firmware provides _DSD or not.
>
> > Now, if there's no DT or no _DSD in the ACPI tables for the given device
> > *and* the driver wants to use its GPIOs anyway, it has to be ACPI-aware to
> > some extent, because in that case the device ID it has been matched against
> > tells it what the meaning of the GpioIo resources in the _CRS is.
> >
> > Then, the driver needs to do something like:
> >
> > if (!device_property_present(dev, "known_property_that_should_be_present")
> > && ACPI_COMPANION(dev))
> > acpi_probe_gpios(dev);
>
> Indeed we can use similar pattern to detect if we have _DSD present or
> not.
>
> > and in the acpi_probe_gpios() routine there may be checks like:
> >
> > if (device_has_id(dev, "MARY0001")) {
> > The first pin in the first GpioIo resource in _CRS is "fred" and
> > it is active-low.
> > The third pin in the second GpioIo resource in _CRS is "steve"
> > and it is not active-low.
> > } else if (device_has_id(dev, "JANE0002")) {
> > The first pin in the second GpioIo resource in _CRS is "fred" and
> > it is not active-low.
> > The second pin in the first GpioIo resource in _CRS is "steve"
> > and it is active-low.
> > }
> >
> > and so on. Of course, there may be drivers knowing that the meaning of the
> > GpioIo resources in _CRS is the same for all devices handled by them, in which
> > case they will not need to check device IDs, but the core has now way of
> > knowing that. Only the drivers have that information and the core has now
> > way to figure out what to do for a given specific device.
> >
> > So here's a radical idea: Why don't we introduce something like
> >
> > acpi_enumerate_gpio(dev, name, GpioIo_index, pin_index, active_low)
> >
> > such that after calling, say, acpi_enumerate_gpio(dev, "fred", 0, 0, true) the
> > driver can do something like:
> >
> > desc = get_gpiod_by_name(dev, "fred");
> >
> > and it'll all work. Then, the only part of the driver that really needs to be
> > ACPI-specific will be the acpi_probe_gpios() function calling acpi_enumerate_gpio()
> > in accordance with what the device ID is.
> >
> > Thoughts?
>
> I think this is good idea. It solves the rfkill-gpio.c problem with just
> small amount of ACPI specific code.
OK, would the below make sense, then (completely untested, on top of the v6
of the device properties patchset)?
Rafael
---
drivers/acpi/scan.c | 2 +
drivers/gpio/gpiolib-acpi.c | 80 ++++++++++++++++++++++++++++++++++++++++++--
include/acpi/acpi_bus.h | 1
include/linux/acpi.h | 15 ++++++++
4 files changed, 96 insertions(+), 2 deletions(-)
Index: linux-pm/include/acpi/acpi_bus.h
===================================================================
--- linux-pm.orig/include/acpi/acpi_bus.h
+++ linux-pm/include/acpi/acpi_bus.h
@@ -355,6 +355,7 @@ struct acpi_device {
struct list_head node;
struct list_head wakeup_list;
struct list_head del_list;
+ struct list_head driver_gpios;
struct acpi_device_status status;
struct acpi_device_flags flags;
struct acpi_device_pnp pnp;
Index: linux-pm/include/linux/acpi.h
===================================================================
--- linux-pm.orig/include/linux/acpi.h
+++ linux-pm/include/linux/acpi.h
@@ -672,6 +672,21 @@ do { \
#endif
#endif
+#if defined(CONFIG_ACPI) && defined(CONFIG_GPIOLIB)
+int acpi_dev_add_driver_gpio(struct acpi_device *adev, const char *propname,
+ int entry_index, int pin_index, bool active_low);
+void acpi_dev_remove_driver_gpios(struct acpi_device *adev);
+#else
+static inline int acpi_dev_add_driver_gpio(struct acpi_device *adev,
+ const char *propname,
+ int entry_index, int pin_index,
+ bool active_low)
+{
+ return -ENXIO;
+}
+static inline void acpi_dev_remove_driver_gpios(struct acpi_device *adev) {}
+#endif
+
/* Device properties */
#define MAX_ACPI_REFERENCE_ARGS 8
Index: linux-pm/drivers/gpio/gpiolib-acpi.c
===================================================================
--- linux-pm.orig/drivers/gpio/gpiolib-acpi.c
+++ linux-pm/drivers/gpio/gpiolib-acpi.c
@@ -47,6 +47,16 @@ struct acpi_gpio_chip {
struct list_head events;
};
+struct acpi_gpio_data {
+ struct list_head item;
+ char *name;
+ int entry_index;
+ int pin_index;
+ bool active_low;
+};
+
+static DEFINE_MUTEX(driver_gpio_data_lock);
+
static int acpi_gpiochip_find(struct gpio_chip *gc, void *data)
{
if (!gc->dev)
@@ -287,6 +297,70 @@ void acpi_gpiochip_free_interrupts(struc
}
}
+int acpi_dev_add_driver_gpio(struct acpi_device *adev, const char *propname,
+ int entry_index, int pin_index, bool active_low)
+{
+ struct acpi_gpio_data *gd;
+
+ if (!propname)
+ return -EINVAL;
+
+ gd = kzalloc(sizeof(*gd), GFP_KERNEL);
+ if (!gd)
+ return -ENOMEM;
+
+ gd->name = kstrdup(propname, GFP_KERNEL);
+ if (!gd->name) {
+ kfree(gd);
+ return -ENOMEM;
+ }
+ gd->entry_index = entry_index;
+ gd->pin_index = pin_index;
+ gd->active_low = active_low;
+
+ mutex_lock(&driver_gpio_data_lock);
+ list_add_tail(&gd->item, &adev->driver_gpios);
+ mutex_unlock(&driver_gpio_data_lock);
+
+ return 0;
+}
+
+void acpi_dev_remove_driver_gpios(struct acpi_device *adev)
+{
+ struct acpi_gpio_data *gd, *next;
+
+ mutex_lock(&driver_gpio_data_lock);
+ list_for_each_entry_safe(gd, next, &adev->driver_gpios, item) {
+ list_del(&gd->item);
+ kfree(gd->name);
+ kfree(gd);
+ }
+ mutex_unlock(&driver_gpio_data_lock);
+}
+
+static bool acpi_get_driver_gpio_data(struct acpi_device *adev,
+ const char *name,
+ struct acpi_reference_args *args)
+{
+ struct acpi_gpio_data *gd;
+
+ mutex_lock(&driver_gpio_data_lock);
+
+ list_for_each_entry(gd, &adev->driver_gpios, item)
+ if (!strcmp(name, gd->name)) {
+ args->adev = adev;
+ args->args[0] = gd->entry_index;
+ args->args[1] = gd->pin_index;
+ args->args[2] = gd->active_low;
+ args->nargs = 3;
+ return true;
+ }
+
+ mutex_unlock(&driver_gpio_data_lock);
+
+ return false;
+}
+
struct acpi_gpio_lookup {
struct acpi_gpio_info info;
int index;
@@ -372,8 +446,10 @@ struct gpio_desc *acpi_get_gpiod_by_inde
memset(&args, 0, sizeof(args));
ret = acpi_dev_get_property_reference(adev, propname, NULL,
index, &args);
- if (ret)
- return ERR_PTR(ret);
+ if (ret) {
+ if (!acpi_get_driver_gpio_data(adev, propname, &args))
+ return ERR_PTR(ret);
+ }
/*
* The property was found and resolved so need to
Index: linux-pm/drivers/acpi/scan.c
===================================================================
--- linux-pm.orig/drivers/acpi/scan.c
+++ linux-pm/drivers/acpi/scan.c
@@ -1284,6 +1284,7 @@ int acpi_device_add(struct acpi_device *
INIT_LIST_HEAD(&device->wakeup_list);
INIT_LIST_HEAD(&device->physical_node_list);
INIT_LIST_HEAD(&device->del_list);
+ INIT_LIST_HEAD(&device->driver_gpios);
mutex_init(&device->physical_node_lock);
new_bus_id = kzalloc(sizeof(struct acpi_device_bus_id), GFP_KERNEL);
@@ -2354,6 +2355,7 @@ void acpi_bus_trim(struct acpi_device *a
} else {
device_release_driver(&adev->dev);
}
+ acpi_dev_remove_driver_gpios(adev);
/*
* Most likely, the device is going away, so put it into D3cold before
* that.
--
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