On Thursday, October 22, 2015 03:01:45 PM Tomeu Vizoso wrote:
> On 22 October 2015 at 03:02, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote:
> > On Monday, September 21, 2015 04:02:43 PM Tomeu Vizoso wrote:
> >> When adding platform and AMBA devices, set the device node's device
> >> member to point to it.
> >>
> >> This speeds lookups considerably and is safe because we only create one
> >> of these devices for any given device node.
> >>
> >> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>
> >> ---
> >>
> >> Changes in v5:
> >> - Set the pointer to struct device also for AMBA devices
> >> - Unset the pointer to struct device when the platform device is about
> >> to be unregistered
> >> - Increase the reference count of the device before returning from
> >> of_find_device_by_node()
> >>
> >> drivers/of/platform.c | 19 ++++++++++---------
> >> include/linux/of.h | 1 +
> >> 2 files changed, 11 insertions(+), 9 deletions(-)
> >>
> >> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> >> index 1001efaedcb8..408d89f1d124 100644
> >> --- a/drivers/of/platform.c
> >> +++ b/drivers/of/platform.c
> >> @@ -32,11 +32,6 @@ const struct of_device_id of_default_bus_match_table[] = {
> >> {} /* Empty terminated list */
> >> };
> >>
> >> -static int of_dev_node_match(struct device *dev, void *data)
> >> -{
> >> - return dev->of_node == data;
> >> -}
> >> -
> >> /**
> >> * of_find_device_by_node - Find the platform_device associated with a node
> >> * @np: Pointer to device tree node
> >> @@ -45,10 +40,10 @@ static int of_dev_node_match(struct device *dev, void *data)
> >> */
> >> struct platform_device *of_find_device_by_node(struct device_node *np)
> >> {
> >> - struct device *dev;
> >> -
> >> - dev = bus_find_device(&platform_bus_type, NULL, np, of_dev_node_match);
> >> - return dev ? to_platform_device(dev) : NULL;
> >> + if (np->device && np->device->bus == &platform_bus_type &&
> >> + get_device(np->device))
> >> + return to_platform_device(np->device);
> >> + return NULL;
> >> }
> >> EXPORT_SYMBOL(of_find_device_by_node);
> >>
> >> @@ -192,6 +187,8 @@ static struct platform_device *of_platform_device_create_pdata(
> >> goto err_clear_flag;
> >> }
> >>
> >> + np->device = &dev->dev;
> >> +
> >> return dev;
> >>
> >> err_clear_flag:
> >> @@ -272,6 +269,8 @@ static struct amba_device *of_amba_device_create(struct device_node *node,
> >> goto err_free;
> >> }
> >>
> >> + node->device = &dev->dev;
> >> +
> >> return dev;
> >>
> >> err_free:
> >> @@ -476,6 +475,8 @@ static int of_platform_device_destroy(struct device *dev, void *data)
> >> if (of_node_check_flag(dev->of_node, OF_POPULATED_BUS))
> >> device_for_each_child(dev, NULL, of_platform_device_destroy);
> >>
> >> + dev->of_node->device = NULL;
> >> +
> >> if (dev->bus == &platform_bus_type)
> >> platform_device_unregister(to_platform_device(dev));
> >> #ifdef CONFIG_ARM_AMBA
> >> diff --git a/include/linux/of.h b/include/linux/of.h
> >> index 2194b8ca41f9..eb091be0f8ee 100644
> >> --- a/include/linux/of.h
> >> +++ b/include/linux/of.h
> >> @@ -52,6 +52,7 @@ struct device_node {
> >> phandle phandle;
> >> const char *full_name;
> >> struct fwnode_handle fwnode;
> >> + struct device *device;
> >
> > There are cases in which multiple device objects point to the same device_node,
> > so is the single struct device pointer here really sufficient?
>
> Only one struct device is registered for a given DT device node when
> the DT is scanned (otherwise, of_find_device_by_node wouldn't be
> safe).
>
> If some driver makes a struct device to point to a device_node that
> already has a struct device associated with it, that's fine.
Well, once that has happened, your new device pointer in the given device_node
becomes useless. Why exactly is that fine?
Thanks,
Rafael
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