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Date: Sat, 17 Nov 2012 12:24:45 +0100
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Mika Westerberg <mika.westerberg@...ux.intel.com>,
Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Jean Delvare <khali@...ux-fr.org>, ben-linux@...ff.org,
w.sang@...gutronix.de, linux-kernel@...r.kernel.org,
lenb@...nel.org, rafael.j.wysocki@...el.com,
broonie@...nsource.wolfsonmicro.com, grant.likely@...retlab.ca,
linus.walleij@...aro.org, mathias.nyman@...ux.intel.com,
linux-acpi@...r.kernel.org
Subject: Re: [PATCH v2 3/3 UPDATED] i2c / ACPI: add ACPI enumeration support
On Saturday, November 17, 2012 10:03:54 AM Mika Westerberg wrote:
> On Fri, Nov 16, 2012 at 11:46:40PM -0700, Bjorn Helgaas wrote:
[...]
> > In any event, after acpi_i2c_register(), I think we have a set of
> > i2c_client devices (with the above namespace, I assume we'd have two
> > of them). I guess acpi_i2c_find_device() is useful now -- it looks
> > like it takes a "struct device *" (e.g., &client->dev from a struct
> > i2c_client), and and gives you back the acpi_handle corresponding to
> > it?
> >
> > Here's the callchain of that path:
> >
> > acpi_i2c_find_device(struct device *) # acpi_i2c_bus.find_device
> > i2c_verify_client(dev)
> > acpi_walk_namespace
> > acpi_i2c_find_child
> > acpi_bus_get_device
> > acpi_bus_get_status
> > acpi_dev_get_resources(..., acpi_i2c_find_child_address, ...)
> > acpi_i2c_find_child_address
> > found if (SERIAL_BUS && SERIAL_TYPE_I2C && slave_address == xx)
> > acpi_dev_free_resource_list
> > *handle = handle
> >
> > That seems like an awful lot of work to do just to map a struct device
> > * back to the acpi_handle. But I don't have any suggestion; just that
> > observation.
>
> We had similar discussion internally about not using that
> drivers/acpi/glue.c but we decided to use it for now, even if it really
> backwards and makes things hard (like you observed as well). A much better
> way would be just to assign the handle once we make the device but it
> seemed not to be that simple after all.
The problem basically is that acpi_bind_one() creates the "physical_node"
and "firmware_node" sysfs files, so both directories of the device nodes
involved need to exist at this point. Moreover, we want it to be called
before a driver is probed, so that the driver's .probe() routine can use
the information available from ACPI. This means it needs to be called
from device_add() and more-or-less where platform_notify() is called.
That's the reason why we decided to use the code in glue.c for the time
being. If you see a better way to do that, however, I'll be happy to
implement it. :-)
Well, maybe there is one. Perhaps we can make acpi_platform_notify()
call acpi_bind_one() upfront and only if that fails, do the whole
type->find_device() dance? Of course, acpi_bind_one() would need to
be modified slightly too, like in the patch below.
If we did that, acpi_i2c_add_device() would only need to assign acpi_handle
as appropriate before calling i2c_new_device() (and analogously for SPI).
What do you think?
Rafael
---
drivers/acpi/glue.c | 40 +++++++++++++++++++++++++++++++---------
1 file changed, 31 insertions(+), 9 deletions(-)
Index: linux/drivers/acpi/glue.c
===================================================================
--- linux.orig/drivers/acpi/glue.c
+++ linux/drivers/acpi/glue.c
@@ -135,8 +135,12 @@ static int acpi_bind_one(struct device *
int retval = -EINVAL;
if (dev->acpi_handle) {
- dev_warn(dev, "Drivers changed 'acpi_handle'\n");
- return -EINVAL;
+ if (handle) {
+ dev_warn(dev, "ACPI handle is already set\n");
+ return -EINVAL;
+ } else {
+ handle = dev->acpi_handle;
+ }
}
get_device(dev);
@@ -144,32 +148,40 @@ static int acpi_bind_one(struct device *
if (ACPI_FAILURE(status))
goto err;
- physical_node = kzalloc(sizeof(struct acpi_device_physical_node),
- GFP_KERNEL);
+ physical_node = kzalloc(sizeof(*physical_node), GFP_KERNEL);
if (!physical_node) {
retval = -ENOMEM;
goto err;
}
mutex_lock(&acpi_dev->physical_node_lock);
+
+ /* Sanity check. */
+ list_for_each_entry(physical_node, &acpi_dev->physical_node_list, node)
+ if (physical_node->dev == dev) {
+ dev_warn(dev, "Already associated with ACPI node\n");
+ retval = -EINVAL;
+ goto err_free;
+ }
+
/* allocate physical node id according to physical_node_id_bitmap */
physical_node->node_id =
find_first_zero_bit(acpi_dev->physical_node_id_bitmap,
ACPI_MAX_PHYSICAL_NODE);
if (physical_node->node_id >= ACPI_MAX_PHYSICAL_NODE) {
retval = -ENOSPC;
- mutex_unlock(&acpi_dev->physical_node_lock);
- kfree(physical_node);
- goto err;
+ goto err_free;
}
set_bit(physical_node->node_id, acpi_dev->physical_node_id_bitmap);
physical_node->dev = dev;
list_add_tail(&physical_node->node, &acpi_dev->physical_node_list);
acpi_dev->physical_node_count++;
+
mutex_unlock(&acpi_dev->physical_node_lock);
- dev->acpi_handle = handle;
+ if (!dev->acpi_handle)
+ dev->acpi_handle = handle;
if (!physical_node->node_id)
strcpy(physical_node_name, PHYSICAL_NODE_STRING);
@@ -189,6 +201,11 @@ static int acpi_bind_one(struct device *
err:
put_device(dev);
return retval;
+
+ err_free:
+ mutex_unlock(&acpi_dev->physical_node_lock);
+ kfree(physical_node);
+ goto err;
}
static int acpi_unbind_one(struct device *dev)
@@ -247,6 +264,10 @@ static int acpi_platform_notify(struct d
acpi_handle handle;
int ret = -EINVAL;
+ ret = acpi_bind_one(dev, NULL);
+ if (!ret)
+ goto out;
+
if (!dev->bus || !dev->parent) {
/* bridge devices genernally haven't bus or parent */
ret = acpi_find_bridge_device(dev, &handle);
@@ -260,10 +281,11 @@ static int acpi_platform_notify(struct d
}
if ((ret = type->find_device(dev, &handle)) != 0)
DBG("Can't get handler for %s\n", dev_name(dev));
- end:
+ end:
if (!ret)
acpi_bind_one(dev, handle);
+ out:
#if ACPI_GLUE_DEBUG
if (!ret) {
struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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