[PATCH 01/10] of: Keep track of populated platform devices

[PATCH 01/10] of: Keep track of populated platform devices

[Pawel Moll]

In "Device Tree powered" systems, platform devices are usually
massively populated with of_platform_populate() call, executed
at some level of initcalls, either by generic architecture
or by platform-specific code.

There are situations though where certain devices must be
created (and bound with drivers) before all the others.
This presents a challenge, as devices created explicitly
would be created again by of_platform_populate().

This patch tries to solve that issue in a generic way,
adding a "populated" flag for a DT node description.
Once set, this device will never be created again via
of_* API, so of_platform_populate() will skip such nodes
(and its children) in a similar way to the non-available
ones.

Cc: devicetree@vger.kernel.org
Signed-off-by: Pawel Moll <pawel.moll@arm.com>
---
 drivers/of/platform.c | 10 ++++++++--
 include/linux/of.h    |  1 +
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index 404d1da..0ae757a 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -204,7 +204,8 @@ static struct platform_device *of_platform_device_create_pdata(
 {
 	struct platform_device *dev;
 
-	if (!of_device_is_available(np))
+	if (!of_device_is_available(np) ||
+			of_node_check_flag(np, OF_POPULATED))
 		return NULL;
 
 	dev = of_device_alloc(np, bus_id, parent);
@@ -230,6 +231,8 @@ static struct platform_device *of_platform_device_create_pdata(
 		return NULL;
 	}
 
+	of_node_set_flag(np, OF_POPULATED);
+
 	return dev;
 }
 
@@ -262,7 +265,8 @@ static struct amba_device *of_amba_device_create(struct device_node *node,
 
 	pr_debug("Creating amba device %s\n", node->full_name);
 
-	if (!of_device_is_available(node))
+	if (!of_device_is_available(node) ||
+			of_node_check_flag(node, OF_POPULATED))
 		return NULL;
 
 	dev = amba_device_alloc(NULL, 0, 0);
@@ -305,6 +309,8 @@ static struct amba_device *of_amba_device_create(struct device_node *node,
 		goto err_free;
 	}
 
+	of_node_set_flag(node, OF_POPULATED);
+
 	return dev;
 
 err_free:
diff --git a/include/linux/of.h b/include/linux/of.h
index 3bad8d1..fd3aaee 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -197,6 +197,7 @@ static inline unsigned long of_read_ulong(const __be32 *cell, int size)
 /* flag descriptions */
 #define OF_DYNAMIC	1 /* node and properties were allocated via kmalloc */
 #define OF_DETACHED	2 /* node has been detached from the device tree */
+#define OF_POPULATED	3 /* device already created for the node */
 
 #define OF_IS_DYNAMIC(x) test_bit(OF_DYNAMIC, &x->_flags)
 #define OF_MARK_DYNAMIC(x) set_bit(OF_DYNAMIC, &x->_flags)
-- 
1.9.1

Re: [PATCH 01/10] of: Keep track of populated platform devices

[Rob Herring]

On Mon, Apr 28, 2014 at 12:57 PM, Pawel Moll <pawel.moll@arm.com> wrote:
> In "Device Tree powered" systems, platform devices are usually
> massively populated with of_platform_populate() call, executed
> at some level of initcalls, either by generic architecture
> or by platform-specific code.
>
> There are situations though where certain devices must be
> created (and bound with drivers) before all the others.
> This presents a challenge, as devices created explicitly
> would be created again by of_platform_populate().
>
> This patch tries to solve that issue in a generic way,
> adding a "populated" flag for a DT node description.
> Once set, this device will never be created again via
> of_* API, so of_platform_populate() will skip such nodes
> (and its children) in a similar way to the non-available
> ones.
>
> Cc: devicetree@vger.kernel.org
> Signed-off-by: Pawel Moll <pawel.moll@arm.com>
> ---
>  drivers/of/platform.c | 10 ++++++++--
>  include/linux/of.h    |  1 +
>  2 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index 404d1da..0ae757a 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -204,7 +204,8 @@ static struct platform_device *of_platform_device_create_pdata(
>  {
>         struct platform_device *dev;
>
> -       if (!of_device_is_available(np))
> +       if (!of_device_is_available(np) ||
> +                       of_node_check_flag(np, OF_POPULATED))

This and the amba case should be a test_and_set operation to avoid a
race condition.

Rob

Re: [PATCH 01/10] of: Keep track of populated platform devices

[Grant Likely]

On Mon, 28 Apr 2014 13:02:28 -0500, Rob Herring <robherring2-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> On Mon, Apr 28, 2014 at 12:57 PM, Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org> wrote:
> > In "Device Tree powered" systems, platform devices are usually
> > massively populated with of_platform_populate() call, executed
> > at some level of initcalls, either by generic architecture
> > or by platform-specific code.
> >
> > There are situations though where certain devices must be
> > created (and bound with drivers) before all the others.
> > This presents a challenge, as devices created explicitly
> > would be created again by of_platform_populate().
> >
> > This patch tries to solve that issue in a generic way,
> > adding a "populated" flag for a DT node description.
> > Once set, this device will never be created again via
> > of_* API, so of_platform_populate() will skip such nodes
> > (and its children) in a similar way to the non-available
> > ones.
> >
> > Cc: devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> > Signed-off-by: Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>
> > ---
> >  drivers/of/platform.c | 10 ++++++++--
> >  include/linux/of.h    |  1 +
> >  2 files changed, 9 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> > index 404d1da..0ae757a 100644
> > --- a/drivers/of/platform.c
> > +++ b/drivers/of/platform.c
> > @@ -204,7 +204,8 @@ static struct platform_device *of_platform_device_create_pdata(
> >  {
> >         struct platform_device *dev;
> >
> > -       if (!of_device_is_available(np))
> > +       if (!of_device_is_available(np) ||
> > +                       of_node_check_flag(np, OF_POPULATED))
> 
> This and the amba case should be a test_and_set operation to avoid a
> race condition.

Yes. It is an unlikely condition at the time that Pawel is handling, but
it should also work for later calls to of_platform_populate() which may
happen at runtime and in parallel.

g.
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Re: [PATCH 01/10] of: Keep track of populated platform devices

[Pawel Moll]

On Tue, 2014-04-29 at 13:56 +0100, Grant Likely wrote:
> > > diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> > > index 404d1da..0ae757a 100644
> > > --- a/drivers/of/platform.c
> > > +++ b/drivers/of/platform.c
> > > @@ -204,7 +204,8 @@ static struct platform_device *of_platform_device_create_pdata(
> > >  {
> > >         struct platform_device *dev;
> > >
> > > -       if (!of_device_is_available(np))
> > > +       if (!of_device_is_available(np) ||
> > > +                       of_node_check_flag(np, OF_POPULATED))
> > 
> > This and the amba case should be a test_and_set operation to avoid a
> > race condition.
> 
> Yes. It is an unlikely condition at the time that Pawel is handling, but
> it should also work for later calls to of_platform_populate() which may
> happen at runtime and in parallel.

Sure thing, will fix.

Thanks!

Pawel

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[PATCH v2] of: Keep track of populated platform devices

[Pawel Moll]

In "Device Tree powered" systems, platform devices are usually
massively populated with of_platform_populate() call, executed
at some level of initcalls, either by generic architecture
or by platform-specific code.

There are situations though where certain devices must be
created (and bound with drivers) before all the others.
This presents a challenge, as devices created explicitly
would be created again by of_platform_populate().

This patch tries to solve that issue in a generic way,
adding a "populated" flag for a DT node description.
Once set, this device will never be created again via
of_* API, so of_platform_populate() will skip such nodes
(and its children) in a similar way to the non-available
ones.

Signed-off-by: Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>
---

Changes since v1:

- added of_node_check_and_set_flag()... (atomic test and set)
- ... used it to atomically mark a node...
- ... clearing the bit on error path.

 drivers/of/platform.c | 18 +++++++++++++-----
 include/linux/of.h    |  7 +++++++
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index 404d1da..b33927a 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -204,12 +204,13 @@ static struct platform_device *of_platform_device_create_pdata(
 {
 	struct platform_device *dev;
 
-	if (!of_device_is_available(np))
+	if (!of_device_is_available(np) ||
+			of_node_check_and_set_flag(np, OF_POPULATED))
 		return NULL;
 
 	dev = of_device_alloc(np, bus_id, parent);
 	if (!dev)
-		return NULL;
+		goto err_clear_flag;
 
 #if defined(CONFIG_MICROBLAZE)
 	dev->archdata.dma_mask = 0xffffffffUL;
@@ -227,10 +228,14 @@ static struct platform_device *of_platform_device_create_pdata(
 
 	if (of_device_add(dev) != 0) {
 		platform_device_put(dev);
-		return NULL;
+		goto err_clear_flag;
 	}
 
 	return dev;
+
+err_clear_flag:
+	of_node_clear_flag(np, OF_POPULATED);
+	return NULL;
 }
 
 /**
@@ -262,14 +267,15 @@ static struct amba_device *of_amba_device_create(struct device_node *node,
 
 	pr_debug("Creating amba device %s\n", node->full_name);
 
-	if (!of_device_is_available(node))
+	if (!of_device_is_available(node) ||
+			of_node_check_and_set_flag(node, OF_POPULATED))
 		return NULL;
 
 	dev = amba_device_alloc(NULL, 0, 0);
 	if (!dev) {
 		pr_err("%s(): amba_device_alloc() failed for %s\n",
 		       __func__, node->full_name);
-		return NULL;
+		goto err_clear_flag;
 	}
 
 	/* setup generic device info */
@@ -309,6 +315,8 @@ static struct amba_device *of_amba_device_create(struct device_node *node,
 
 err_free:
 	amba_device_put(dev);
+err_clear_flag:
+	of_node_clear_flag(node, OF_POPULATED);
 	return NULL;
 }
 #else /* CONFIG_ARM_AMBA */
diff --git a/include/linux/of.h b/include/linux/of.h
index 3bad8d1..534cab8 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -130,6 +130,12 @@ static inline int of_node_check_flag(struct device_node *n, unsigned long flag)
 	return test_bit(flag, &n->_flags);
 }
 
+static inline int of_node_check_and_set_flag(struct device_node *n,
+		unsigned long flag)
+{
+	return test_and_set_bit(flag, &n->_flags);
+}
+
 static inline void of_node_set_flag(struct device_node *n, unsigned long flag)
 {
 	set_bit(flag, &n->_flags);
@@ -197,6 +203,7 @@ static inline unsigned long of_read_ulong(const __be32 *cell, int size)
 /* flag descriptions */
 #define OF_DYNAMIC	1 /* node and properties were allocated via kmalloc */
 #define OF_DETACHED	2 /* node has been detached from the device tree */
+#define OF_POPULATED	3 /* device already created for the node */
 
 #define OF_IS_DYNAMIC(x) test_bit(OF_DYNAMIC, &x->_flags)
 #define OF_MARK_DYNAMIC(x) set_bit(OF_DYNAMIC, &x->_flags)
-- 
1.9.1

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Re: [PATCH v2] of: Keep track of populated platform devices

[Rob Herring]

On Wed, Apr 30, 2014 at 9:05 AM, Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org> wrote:
> In "Device Tree powered" systems, platform devices are usually
> massively populated with of_platform_populate() call, executed
> at some level of initcalls, either by generic architecture
> or by platform-specific code.
>
> There are situations though where certain devices must be
> created (and bound with drivers) before all the others.
> This presents a challenge, as devices created explicitly
> would be created again by of_platform_populate().
>
> This patch tries to solve that issue in a generic way,
> adding a "populated" flag for a DT node description.
> Once set, this device will never be created again via
> of_* API, so of_platform_populate() will skip such nodes
> (and its children) in a similar way to the non-available
> ones.
>
> Signed-off-by: Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>

One pondering and one minor change below, otherwise:

Acked-by: Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>


> ---
>
> Changes since v1:
>
> - added of_node_check_and_set_flag()... (atomic test and set)
> - ... used it to atomically mark a node...
> - ... clearing the bit on error path.
>
>  drivers/of/platform.c | 18 +++++++++++++-----
>  include/linux/of.h    |  7 +++++++
>  2 files changed, 20 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index 404d1da..b33927a 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -204,12 +204,13 @@ static struct platform_device *of_platform_device_create_pdata(
>  {
>         struct platform_device *dev;
>
> -       if (!of_device_is_available(np))
> +       if (!of_device_is_available(np) ||
> +                       of_node_check_and_set_flag(np, OF_POPULATED))
>                 return NULL;
>
>         dev = of_device_alloc(np, bus_id, parent);
>         if (!dev)
> -               return NULL;
> +               goto err_clear_flag;

I wonder if leaving it set would be the right behavior. I can't see
that we would want to process the node again. But this is the
exceptional case, so its probably not too important and can stay like
this.

>
>  #if defined(CONFIG_MICROBLAZE)
>         dev->archdata.dma_mask = 0xffffffffUL;
> @@ -227,10 +228,14 @@ static struct platform_device *of_platform_device_create_pdata(
>
>         if (of_device_add(dev) != 0) {
>                 platform_device_put(dev);
> -               return NULL;
> +               goto err_clear_flag;
>         }
>
>         return dev;
> +
> +err_clear_flag:
> +       of_node_clear_flag(np, OF_POPULATED);
> +       return NULL;
>  }
>
>  /**
> @@ -262,14 +267,15 @@ static struct amba_device *of_amba_device_create(struct device_node *node,
>
>         pr_debug("Creating amba device %s\n", node->full_name);
>
> -       if (!of_device_is_available(node))
> +       if (!of_device_is_available(node) ||
> +                       of_node_check_and_set_flag(node, OF_POPULATED))
>                 return NULL;
>
>         dev = amba_device_alloc(NULL, 0, 0);
>         if (!dev) {
>                 pr_err("%s(): amba_device_alloc() failed for %s\n",
>                        __func__, node->full_name);
> -               return NULL;
> +               goto err_clear_flag;
>         }
>
>         /* setup generic device info */
> @@ -309,6 +315,8 @@ static struct amba_device *of_amba_device_create(struct device_node *node,
>
>  err_free:
>         amba_device_put(dev);
> +err_clear_flag:
> +       of_node_clear_flag(node, OF_POPULATED);
>         return NULL;
>  }
>  #else /* CONFIG_ARM_AMBA */
> diff --git a/include/linux/of.h b/include/linux/of.h
> index 3bad8d1..534cab8 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -130,6 +130,12 @@ static inline int of_node_check_flag(struct device_node *n, unsigned long flag)
>         return test_bit(flag, &n->_flags);
>  }
>
> +static inline int of_node_check_and_set_flag(struct device_node *n,

Please keep the well known naming convention of the called function:
of_node_test_and_set_flag
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Re: [PATCH v2] of: Keep track of populated platform devices

[Grant Likely]

On Wed, 30 Apr 2014 10:22:25 -0500, Rob Herring <robherring2-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> On Wed, Apr 30, 2014 at 9:05 AM, Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org> wrote:
> > In "Device Tree powered" systems, platform devices are usually
> > massively populated with of_platform_populate() call, executed
> > at some level of initcalls, either by generic architecture
> > or by platform-specific code.
> >
> > There are situations though where certain devices must be
> > created (and bound with drivers) before all the others.
> > This presents a challenge, as devices created explicitly
> > would be created again by of_platform_populate().
> >
> > This patch tries to solve that issue in a generic way,
> > adding a "populated" flag for a DT node description.
> > Once set, this device will never be created again via
> > of_* API, so of_platform_populate() will skip such nodes
> > (and its children) in a similar way to the non-available
> > ones.
> >
> > Signed-off-by: Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>
> 
> One pondering and one minor change below, otherwise:
> 
> Acked-by: Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> 
> 
> > ---
> >
> > Changes since v1:
> >
> > - added of_node_check_and_set_flag()... (atomic test and set)
> > - ... used it to atomically mark a node...
> > - ... clearing the bit on error path.
> >
> >  drivers/of/platform.c | 18 +++++++++++++-----
> >  include/linux/of.h    |  7 +++++++
> >  2 files changed, 20 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> > index 404d1da..b33927a 100644
> > --- a/drivers/of/platform.c
> > +++ b/drivers/of/platform.c
> > @@ -204,12 +204,13 @@ static struct platform_device *of_platform_device_create_pdata(
> >  {
> >         struct platform_device *dev;
> >
> > -       if (!of_device_is_available(np))
> > +       if (!of_device_is_available(np) ||
> > +                       of_node_check_and_set_flag(np, OF_POPULATED))
> >                 return NULL;
> >
> >         dev = of_device_alloc(np, bus_id, parent);
> >         if (!dev)
> > -               return NULL;
> > +               goto err_clear_flag;
> 
> I wonder if leaving it set would be the right behavior. I can't see
> that we would want to process the node again. But this is the
> exceptional case, so its probably not too important and can stay like
> this.

That doesn't work in the case where drivers use of_platform_populate().
MFD devices in particular make use of it. If the driver does not get
cleared on removal of the devices, then all MFD users will be broken on
driver unbind/rebind. *

We really need to have the inverse of of_platform_populate which will
remove all child and child's child devices and clear all flags and such.
Right now moany drivers are open-coding the removal.

* most drivers are somewhat broken on unbind/rebind anyway, but I don't
  want to make it impossible for a driver to get it right.

> 
> >
> >  #if defined(CONFIG_MICROBLAZE)
> >         dev->archdata.dma_mask = 0xffffffffUL;
> > @@ -227,10 +228,14 @@ static struct platform_device *of_platform_device_create_pdata(
> >
> >         if (of_device_add(dev) != 0) {
> >                 platform_device_put(dev);
> > -               return NULL;
> > +               goto err_clear_flag;
> >         }
> >
> >         return dev;
> > +
> > +err_clear_flag:
> > +       of_node_clear_flag(np, OF_POPULATED);
> > +       return NULL;
> >  }
> >
> >  /**
> > @@ -262,14 +267,15 @@ static struct amba_device *of_amba_device_create(struct device_node *node,
> >
> >         pr_debug("Creating amba device %s\n", node->full_name);
> >
> > -       if (!of_device_is_available(node))
> > +       if (!of_device_is_available(node) ||
> > +                       of_node_check_and_set_flag(node, OF_POPULATED))
> >                 return NULL;
> >
> >         dev = amba_device_alloc(NULL, 0, 0);
> >         if (!dev) {
> >                 pr_err("%s(): amba_device_alloc() failed for %s\n",
> >                        __func__, node->full_name);
> > -               return NULL;
> > +               goto err_clear_flag;
> >         }
> >
> >         /* setup generic device info */
> > @@ -309,6 +315,8 @@ static struct amba_device *of_amba_device_create(struct device_node *node,
> >
> >  err_free:
> >         amba_device_put(dev);
> > +err_clear_flag:
> > +       of_node_clear_flag(node, OF_POPULATED);
> >         return NULL;
> >  }
> >  #else /* CONFIG_ARM_AMBA */
> > diff --git a/include/linux/of.h b/include/linux/of.h
> > index 3bad8d1..534cab8 100644
> > --- a/include/linux/of.h
> > +++ b/include/linux/of.h
> > @@ -130,6 +130,12 @@ static inline int of_node_check_flag(struct device_node *n, unsigned long flag)
> >         return test_bit(flag, &n->_flags);
> >  }
> >
> > +static inline int of_node_check_and_set_flag(struct device_node *n,
> 
> Please keep the well known naming convention of the called function:
> of_node_test_and_set_flag

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Re: [PATCH v2] of: Keep track of populated platform devices

[Grant Likely]

On Thu, May 1, 2014 at 10:26 AM, Grant Likely <grant.likely-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> wrote:
> On Wed, 30 Apr 2014 10:22:25 -0500, Rob Herring <robherring2-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>> On Wed, Apr 30, 2014 at 9:05 AM, Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org> wrote:
>> > In "Device Tree powered" systems, platform devices are usually
>> > massively populated with of_platform_populate() call, executed
>> > at some level of initcalls, either by generic architecture
>> > or by platform-specific code.
>> >
>> > There are situations though where certain devices must be
>> > created (and bound with drivers) before all the others.
>> > This presents a challenge, as devices created explicitly
>> > would be created again by of_platform_populate().
>> >
>> > This patch tries to solve that issue in a generic way,
>> > adding a "populated" flag for a DT node description.
>> > Once set, this device will never be created again via
>> > of_* API, so of_platform_populate() will skip such nodes
>> > (and its children) in a similar way to the non-available
>> > ones.
>> >
>> > Signed-off-by: Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>
>>
>> One pondering and one minor change below, otherwise:
>>
>> Acked-by: Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
>>
>>
>> > ---
>> >
>> > Changes since v1:
>> >
>> > - added of_node_check_and_set_flag()... (atomic test and set)
>> > - ... used it to atomically mark a node...
>> > - ... clearing the bit on error path.
>> >
>> >  drivers/of/platform.c | 18 +++++++++++++-----
>> >  include/linux/of.h    |  7 +++++++
>> >  2 files changed, 20 insertions(+), 5 deletions(-)
>> >
>> > diff --git a/drivers/of/platform.c b/drivers/of/platform.c
>> > index 404d1da..b33927a 100644
>> > --- a/drivers/of/platform.c
>> > +++ b/drivers/of/platform.c
>> > @@ -204,12 +204,13 @@ static struct platform_device *of_platform_device_create_pdata(
>> >  {
>> >         struct platform_device *dev;
>> >
>> > -       if (!of_device_is_available(np))
>> > +       if (!of_device_is_available(np) ||
>> > +                       of_node_check_and_set_flag(np, OF_POPULATED))
>> >                 return NULL;
>> >
>> >         dev = of_device_alloc(np, bus_id, parent);
>> >         if (!dev)
>> > -               return NULL;
>> > +               goto err_clear_flag;
>>
>> I wonder if leaving it set would be the right behavior. I can't see
>> that we would want to process the node again. But this is the
>> exceptional case, so its probably not too important and can stay like
>> this.
>
> That doesn't work in the case where drivers use of_platform_populate().
> MFD devices in particular make use of it. If the driver does not get
> cleared on removal of the devices, then all MFD users will be broken on
> driver unbind/rebind. *
>
> We really need to have the inverse of of_platform_populate which will
> remove all child and child's child devices and clear all flags and such.
> Right now moany drivers are open-coding the removal.
>
> * most drivers are somewhat broken on unbind/rebind anyway, but I don't
>   want to make it impossible for a driver to get it right.

The function shouldn't be too difficult. I would expect it to look
something like this. You'll need to check the details.

static int __of_platform_unpopulate_device(struct device *dev, void *c)
{
    if (!dev->of_node || !of_node_get_flag(dev->of_node, OF_POPULATED)
        return 0;

    // recursively remove the children too --- I'd like to find a way
to do this non-recursively
    device_for_each_child(dev, NULL, __of_platform_unpopulate_device);

    // Need to check if the device should be explicitly unbound from
it's driver before removing it. However, I think the driver core takes
care of this for us.

    // Remove based on the bus type
    switch (dev->bus) {
        case &platform_bus_type:
            platform_device_remove(to_platform_device(dev));
            break;
        case &amba_bus_type:
            amba_device_remove(to_platform_device(dev));
            break;
    }

    // Should check here if there are any other children to the
device. It is probably bad to remove a device that still has children.
Need to check what the driver core will do.
}

void of_platform_unpopulate(struct device *parent)
{
    device_for_each_child(parent, NULL, __of_platform_unpopulate_device);
}

>
>>
>> >
>> >  #if defined(CONFIG_MICROBLAZE)
>> >         dev->archdata.dma_mask = 0xffffffffUL;
>> > @@ -227,10 +228,14 @@ static struct platform_device *of_platform_device_create_pdata(
>> >
>> >         if (of_device_add(dev) != 0) {
>> >                 platform_device_put(dev);
>> > -               return NULL;
>> > +               goto err_clear_flag;
>> >         }
>> >
>> >         return dev;
>> > +
>> > +err_clear_flag:
>> > +       of_node_clear_flag(np, OF_POPULATED);
>> > +       return NULL;
>> >  }
>> >
>> >  /**
>> > @@ -262,14 +267,15 @@ static struct amba_device *of_amba_device_create(struct device_node *node,
>> >
>> >         pr_debug("Creating amba device %s\n", node->full_name);
>> >
>> > -       if (!of_device_is_available(node))
>> > +       if (!of_device_is_available(node) ||
>> > +                       of_node_check_and_set_flag(node, OF_POPULATED))
>> >                 return NULL;
>> >
>> >         dev = amba_device_alloc(NULL, 0, 0);
>> >         if (!dev) {
>> >                 pr_err("%s(): amba_device_alloc() failed for %s\n",
>> >                        __func__, node->full_name);
>> > -               return NULL;
>> > +               goto err_clear_flag;
>> >         }
>> >
>> >         /* setup generic device info */
>> > @@ -309,6 +315,8 @@ static struct amba_device *of_amba_device_create(struct device_node *node,
>> >
>> >  err_free:
>> >         amba_device_put(dev);
>> > +err_clear_flag:
>> > +       of_node_clear_flag(node, OF_POPULATED);
>> >         return NULL;
>> >  }
>> >  #else /* CONFIG_ARM_AMBA */
>> > diff --git a/include/linux/of.h b/include/linux/of.h
>> > index 3bad8d1..534cab8 100644
>> > --- a/include/linux/of.h
>> > +++ b/include/linux/of.h
>> > @@ -130,6 +130,12 @@ static inline int of_node_check_flag(struct device_node *n, unsigned long flag)
>> >         return test_bit(flag, &n->_flags);
>> >  }
>> >
>> > +static inline int of_node_check_and_set_flag(struct device_node *n,
>>
>> Please keep the well known naming convention of the called function:
>> of_node_test_and_set_flag
>
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Re: [PATCH v2] of: Keep track of populated platform devices

[Pawel Moll]

On Thu, 2014-05-01 at 10:43 +0100, Grant Likely wrote:
> > That doesn't work in the case where drivers use of_platform_populate().
> > MFD devices in particular make use of it. If the driver does not get
> > cleared on removal of the devices, then all MFD users will be broken on
> > driver unbind/rebind. *
> >
> > We really need to have the inverse of of_platform_populate which will
> > remove all child and child's child devices and clear all flags and such.
> > Right now moany drivers are open-coding the removal.

Agreed, but, unless I'm missing some fundamental issue, I believe we can
solve the flag clearing problem in a generic way:

--8<-----------
diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
index 3cf61a1..0f489fb 100644
--- a/drivers/amba/bus.c
+++ b/drivers/amba/bus.c
@@ -17,6 +17,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/amba/bus.h>
 #include <linux/sizes.h>
+#include <linux/of_device.h>
 
 #include <asm/irq.h>
 
@@ -268,6 +269,7 @@ static void amba_device_release(struct device *dev)
 {
 	struct amba_device *d = to_amba_device(dev);
 
+	of_device_node_put(dev);
 	if (d->res.parent)
 		release_resource(&d->res);
 	kfree(d);
diff --git a/include/linux/of_device.h b/include/linux/of_device.h
index ef37021..fd14d46 100644
--- a/include/linux/of_device.h
+++ b/include/linux/of_device.h
@@ -41,6 +41,8 @@ extern int of_device_uevent_modalias(struct device *dev, struct kobj_uevent_env
 
 static inline void of_device_node_put(struct device *dev)
 {
+	if (dev->of_node)
+		of_node_clear_flag(dev->of_node, OF_POPULATED);
 	of_node_put(dev->of_node);
 }
--8<-----------

This will work even if one manually unregisters a DT-originating device,
because of_device_node_put() would be called in both amba and platform
device (kobj) release path.

By the way, the fact that today amba_device_release() doesn't do
of_device_node_put() seems like a bug to me? (node's reference counter
won't be decremented)

> The function shouldn't be too difficult. I would expect it to look
> something like this. You'll need to check the details.

8<-----------
diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index dd4328c..b6b5a2b 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -493,4 +493,49 @@ int of_platform_populate(struct device_node *root,
 	return rc;
 }
 EXPORT_SYMBOL_GPL(of_platform_populate);
+
+static int of_platform_device_destroy(struct device *dev, void *data)
+{
+	int *parents_children_left = data;
+	int my_children_left = 0;
+
+	/* Do not touch devices not populated from the device tree */
+	if (!dev->of_node || !of_node_check_flag(dev->of_node, OF_POPULATED)) {
+		*parents_children_left++;
+		return 0;
+	}
+
+	device_for_each_child(dev, &my_children_left,
+			of_platform_device_destroy);
+	if (my_children_left) {
+		*parents_children_left++;
+		return 0;
+	}
+
+	if (dev->bus == &platform_bus_type)
+		platform_device_unregister(to_platform_device(dev));
+	else if (dev->bus == &amba_bustype)
+		amba_device_unregister(to_amba_device(dev));
+
+	return 0;
+}
+
+/**
+ * of_platform_depopulate() - Remove devices populated from device tree
+ * @parent: device which childred will be removed
+ *
+ * Complementary to of_platform_populate(), this function removes children
+ * of the given device (and, recurrently, their children) that have been
+ * created from their respective device tree nodes (and only those,
+ * leaving others - eg. manually created - unharmed). */
+ */
+int of_platform_depopulate(struct device *parent)
+{
+	int children_left = 0;
+
+	device_for_each_child(dev, &children_left, of_platform_device_destroy);
+
+	return children_left ? -EBUSY : 0;
+}
+EXPORT_SYMBOL_GPL(of_platform_depopulate);
 #endif /* CONFIG_OF_ADDRESS */
diff --git a/include/linux/of_platform.h b/include/linux/of_platform.h
index 05cb4a9..ef4f4ad 100644
--- a/include/linux/of_platform.h
+++ b/include/linux/of_platform.h
@@ -72,6 +72,7 @@ extern int of_platform_populate(struct device_node *root,
 				const struct of_device_id *matches,
 				const struct of_dev_auxdata *lookup,
 				struct device *parent);
+static inline int of_platform_depopulate(struct device *parent);
 #else
 static inline int of_platform_populate(struct device_node *root,
 					const struct of_device_id *matches,
@@ -80,6 +81,10 @@ static inline int of_platform_populate(struct device_node *root,
 {
 	return -ENODEV;
 }
+static inline int of_platform_depopulate(struct device *parent)
+{
+	return -ENODEV;
+}
 #endif
 
 #endif	/* _LINUX_OF_PLATFORM_H */
8<-----------

> static int __of_platform_unpopulate_device(struct device *dev, void *c)
> {
>     if (!dev->of_node || !of_node_get_flag(dev->of_node, OF_POPULATED)
>         return 0;
> 
>     // recursively remove the children too --- I'd like to find a way
> to do this non-recursively
>     device_for_each_child(dev, NULL, __of_platform_unpopulate_device);

As of_platform_populate() is recursive itself, I don't see much problem
with this.

>     // Need to check if the device should be explicitly unbound from
> it's driver before removing it. However, I think the driver core takes
> care of this for us.

Yep, removing either a driver or a device unbinds all existing pairs.

>     // Remove based on the bus type
>     switch (dev->bus) {
>         case &platform_bus_type:

To my surprise gcc said "error: pointers are not permitted as case
values". One learns every day ;-)

>             platform_device_remove(to_platform_device(dev));
>             break;
>         case &amba_bus_type:
>             amba_device_remove(to_platform_device(dev));
>             break;
>     }
> 
>     // Should check here if there are any other children to the
> device. It is probably bad to remove a device that still has children.
> Need to check what the driver core will do.
> }

The reference count will be still be greater than 0, so the parent won't
be harmed. Nevertheless it's better to consciously handle such case. At
least I tried.

Pawel

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[PATCH v3] of: Keep track of populated platform devices

[Pawel Moll]

In "Device Tree powered" systems, platform devices are usually
massively populated with of_platform_populate() call, executed
at some level of initcalls, either by generic architecture
or by platform-specific code.

There are situations though where certain devices must be
created (and bound with drivers) before all the others.
This presents a challenge, as devices created explicitly
would be created again by of_platform_populate().

This patch tries to solve that issue in a generic way,
adding a "populated" flag for a DT node description.
Once set, this device will never be created again via
of_* API, so of_platform_populate() will skip such nodes
(and its children) in a similar way to the non-available
ones.

The flag is cleared when a device is being removed and
returns the DT node by calling of_device_node_put() (it
was missing from the amba device release function, added).

Signed-off-by: Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>
---
Changes since v2:

- the populated flag is now cleared when the device
  is being removed by platform or amba bus code
- added missing of_device_node_put() to amba_device_release()
- renamed of_node_check_and_set_flag() to
  of_node_check_test_and_set_flag() to follow the
  bitops naming convention
- didn't add Rob's ack as the patch changed too much

Changes since v1:

- added of_node_check_and_set_flag()... (atomic test and set)
- ... used it to atomically mark a node...
- ... clearing the bit on error path.

 drivers/amba/bus.c        |  2 ++
 drivers/of/platform.c     | 18 +++++++++++++-----
 include/linux/of.h        |  7 +++++++
 include/linux/of_device.h |  2 ++
 4 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
index 3cf61a1..0f489fb 100644
--- a/drivers/amba/bus.c
+++ b/drivers/amba/bus.c
@@ -17,6 +17,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/amba/bus.h>
 #include <linux/sizes.h>
+#include <linux/of_device.h>
 
 #include <asm/irq.h>
 
@@ -268,6 +269,7 @@ static void amba_device_release(struct device *dev)
 {
 	struct amba_device *d = to_amba_device(dev);
 
+	of_device_node_put(dev);
 	if (d->res.parent)
 		release_resource(&d->res);
 	kfree(d);
diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index bd47fbc..2d0c8b7 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -206,12 +206,13 @@ static struct platform_device *of_platform_device_create_pdata(
 {
 	struct platform_device *dev;
 
-	if (!of_device_is_available(np))
+	if (!of_device_is_available(np) ||
+			of_node_test_and_set_flag(np, OF_POPULATED))
 		return NULL;
 
 	dev = of_device_alloc(np, bus_id, parent);
 	if (!dev)
-		return NULL;
+		goto err_clear_flag;
 
 #if defined(CONFIG_MICROBLAZE)
 	dev->archdata.dma_mask = 0xffffffffUL;
@@ -229,10 +230,14 @@ static struct platform_device *of_platform_device_create_pdata(
 
 	if (of_device_add(dev) != 0) {
 		platform_device_put(dev);
-		return NULL;
+		goto err_clear_flag;
 	}
 
 	return dev;
+
+err_clear_flag:
+	of_node_clear_flag(np, OF_POPULATED);
+	return NULL;
 }
 
 /**
@@ -264,14 +269,15 @@ static struct amba_device *of_amba_device_create(struct device_node *node,
 
 	pr_debug("Creating amba device %s\n", node->full_name);
 
-	if (!of_device_is_available(node))
+	if (!of_device_is_available(node) ||
+			of_node_test_and_set_flag(node, OF_POPULATED))
 		return NULL;
 
 	dev = amba_device_alloc(NULL, 0, 0);
 	if (!dev) {
 		pr_err("%s(): amba_device_alloc() failed for %s\n",
 		       __func__, node->full_name);
-		return NULL;
+		goto err_clear_flag;
 	}
 
 	/* setup generic device info */
@@ -311,6 +317,8 @@ static struct amba_device *of_amba_device_create(struct device_node *node,
 
 err_free:
 	amba_device_put(dev);
+err_clear_flag:
+	of_node_clear_flag(node, OF_POPULATED);
 	return NULL;
 }
 #else /* CONFIG_ARM_AMBA */
diff --git a/include/linux/of.h b/include/linux/of.h
index 3bad8d1..3fd6079 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -130,6 +130,12 @@ static inline int of_node_check_flag(struct device_node *n, unsigned long flag)
 	return test_bit(flag, &n->_flags);
 }
 
+static inline int of_node_test_and_set_flag(struct device_node *n,
+		unsigned long flag)
+{
+	return test_and_set_bit(flag, &n->_flags);
+}
+
 static inline void of_node_set_flag(struct device_node *n, unsigned long flag)
 {
 	set_bit(flag, &n->_flags);
@@ -197,6 +203,7 @@ static inline unsigned long of_read_ulong(const __be32 *cell, int size)
 /* flag descriptions */
 #define OF_DYNAMIC	1 /* node and properties were allocated via kmalloc */
 #define OF_DETACHED	2 /* node has been detached from the device tree */
+#define OF_POPULATED	3 /* device already created for the node */
 
 #define OF_IS_DYNAMIC(x) test_bit(OF_DYNAMIC, &x->_flags)
 #define OF_MARK_DYNAMIC(x) set_bit(OF_DYNAMIC, &x->_flags)
diff --git a/include/linux/of_device.h b/include/linux/of_device.h
index ef37021..fd14d46 100644
--- a/include/linux/of_device.h
+++ b/include/linux/of_device.h
@@ -41,6 +41,8 @@ extern int of_device_uevent_modalias(struct device *dev, struct kobj_uevent_env
 
 static inline void of_device_node_put(struct device *dev)
 {
+	if (dev->of_node)
+		of_node_clear_flag(dev->of_node, OF_POPULATED);
 	of_node_put(dev->of_node);
 }
 
-- 
1.9.1

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Re: [PATCH v3] of: Keep track of populated platform devices

[Rob Herring]

On Tue, May 13, 2014 at 6:48 AM, Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org> wrote:
> In "Device Tree powered" systems, platform devices are usually
> massively populated with of_platform_populate() call, executed
> at some level of initcalls, either by generic architecture
> or by platform-specific code.
>
> There are situations though where certain devices must be
> created (and bound with drivers) before all the others.
> This presents a challenge, as devices created explicitly
> would be created again by of_platform_populate().
>
> This patch tries to solve that issue in a generic way,
> adding a "populated" flag for a DT node description.
> Once set, this device will never be created again via
> of_* API, so of_platform_populate() will skip such nodes
> (and its children) in a similar way to the non-available
> ones.
>
> The flag is cleared when a device is being removed and
> returns the DT node by calling of_device_node_put() (it
> was missing from the amba device release function, added).
>
> Signed-off-by: Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>

A few formatting nits, but otherwise:

Reviewed-by: Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>

[..]

> @@ -206,12 +206,13 @@ static struct platform_device *of_platform_device_create_pdata(
>  {
>         struct platform_device *dev;
>
> -       if (!of_device_is_available(np))
> +       if (!of_device_is_available(np) ||
> +                       of_node_test_and_set_flag(np, OF_POPULATED))

This should be lined up with the ! on the previous line.


> @@ -264,14 +269,15 @@ static struct amba_device *of_amba_device_create(struct device_node *node,
>
>         pr_debug("Creating amba device %s\n", node->full_name);
>
> -       if (!of_device_is_available(node))
> +       if (!of_device_is_available(node) ||
> +                       of_node_test_and_set_flag(node, OF_POPULATED))

And this one.

>                 return NULL;

Rob
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Re: [PATCH v2] of: Keep track of populated platform devices

[Grant Likely]

On Wed, 07 May 2014 15:37:17 +0100, Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org> wrote:
> On Thu, 2014-05-01 at 10:43 +0100, Grant Likely wrote:
> > > That doesn't work in the case where drivers use of_platform_populate().
> > > MFD devices in particular make use of it. If the driver does not get
> > > cleared on removal of the devices, then all MFD users will be broken on
> > > driver unbind/rebind. *
> > >
> > > We really need to have the inverse of of_platform_populate which will
> > > remove all child and child's child devices and clear all flags and such.
> > > Right now moany drivers are open-coding the removal.
> 
> Agreed, but, unless I'm missing some fundamental issue, I believe we can
> solve the flag clearing problem in a generic way:
> 
> --8<-----------
> diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
> index 3cf61a1..0f489fb 100644
> --- a/drivers/amba/bus.c
> +++ b/drivers/amba/bus.c
> @@ -17,6 +17,7 @@
>  #include <linux/pm_runtime.h>
>  #include <linux/amba/bus.h>
>  #include <linux/sizes.h>
> +#include <linux/of_device.h>
>  
>  #include <asm/irq.h>
>  
> @@ -268,6 +269,7 @@ static void amba_device_release(struct device *dev)
>  {
>  	struct amba_device *d = to_amba_device(dev);
>  
> +	of_device_node_put(dev);
>  	if (d->res.parent)
>  		release_resource(&d->res);
>  	kfree(d);
> diff --git a/include/linux/of_device.h b/include/linux/of_device.h
> index ef37021..fd14d46 100644
> --- a/include/linux/of_device.h
> +++ b/include/linux/of_device.h
> @@ -41,6 +41,8 @@ extern int of_device_uevent_modalias(struct device *dev, struct kobj_uevent_env
>  
>  static inline void of_device_node_put(struct device *dev)
>  {
> +	if (dev->of_node)
> +		of_node_clear_flag(dev->of_node, OF_POPULATED);
>  	of_node_put(dev->of_node);
>  }
> --8<-----------
> 
> This will work even if one manually unregisters a DT-originating device,
> because of_device_node_put() would be called in both amba and platform
> device (kobj) release path.

Doing it that way will also catch platform_devices that were created
apart from of_platform_populate() and manually attached to an of_node,
which is done some times. It will also break whenever multiple devices
reference the same node if they call of_device_node_put().

For example, a platform device providing an i2c bus will have a child
device that represents the i2c bus, and that i2c device will point to
the same node.

The flag clear really does need to be kept in the
platform_device_unpopulate path because it is only to be used internally
by of_platform_{populate,depopulate}

> 
> By the way, the fact that today amba_device_release() doesn't do
> of_device_node_put() seems like a bug to me? (node's reference counter
> won't be decremented)

Yes, that is a bug. I want to get some unittests added to the DT code to
verify that reference counts are being tracked correctly. Right now it
is an utter mess.

> 
> > The function shouldn't be too difficult. I would expect it to look
> > something like this. You'll need to check the details.
> 
> 8<-----------
> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index dd4328c..b6b5a2b 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -493,4 +493,49 @@ int of_platform_populate(struct device_node *root,
>  	return rc;
>  }
>  EXPORT_SYMBOL_GPL(of_platform_populate);
> +
> +static int of_platform_device_destroy(struct device *dev, void *data)
> +{
> +	int *parents_children_left = data;
> +	int my_children_left = 0;
> +
> +	/* Do not touch devices not populated from the device tree */
> +	if (!dev->of_node || !of_node_check_flag(dev->of_node, OF_POPULATED)) {
> +		*parents_children_left++;
> +		return 0;
> +	}
> +
> +	device_for_each_child(dev, &my_children_left,
> +			of_platform_device_destroy);
> +	if (my_children_left) {
> +		*parents_children_left++;
> +		return 0;
> +	}
> +
> +	if (dev->bus == &platform_bus_type)
> +		platform_device_unregister(to_platform_device(dev));
> +	else if (dev->bus == &amba_bustype)
> +		amba_device_unregister(to_amba_device(dev));
> +
> +	return 0;
> +}

This new code looks good to me. I haven't done any testing though.

Acked-by: Grant Likely <grant.likely-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>

> +
> +/**
> + * of_platform_depopulate() - Remove devices populated from device tree
> + * @parent: device which childred will be removed
> + *
> + * Complementary to of_platform_populate(), this function removes children
> + * of the given device (and, recurrently, their children) that have been
> + * created from their respective device tree nodes (and only those,
> + * leaving others - eg. manually created - unharmed). */
> + */
> +int of_platform_depopulate(struct device *parent)
> +{
> +	int children_left = 0;
> +
> +	device_for_each_child(dev, &children_left, of_platform_device_destroy);
> +
> +	return children_left ? -EBUSY : 0;
> +}
> +EXPORT_SYMBOL_GPL(of_platform_depopulate);
>  #endif /* CONFIG_OF_ADDRESS */
> diff --git a/include/linux/of_platform.h b/include/linux/of_platform.h
> index 05cb4a9..ef4f4ad 100644
> --- a/include/linux/of_platform.h
> +++ b/include/linux/of_platform.h
> @@ -72,6 +72,7 @@ extern int of_platform_populate(struct device_node *root,
>  				const struct of_device_id *matches,
>  				const struct of_dev_auxdata *lookup,
>  				struct device *parent);
> +static inline int of_platform_depopulate(struct device *parent);
>  #else
>  static inline int of_platform_populate(struct device_node *root,
>  					const struct of_device_id *matches,
> @@ -80,6 +81,10 @@ static inline int of_platform_populate(struct device_node *root,
>  {
>  	return -ENODEV;
>  }
> +static inline int of_platform_depopulate(struct device *parent)
> +{
> +	return -ENODEV;
> +}
>  #endif
>  
>  #endif	/* _LINUX_OF_PLATFORM_H */
> 8<-----------
> 
> > static int __of_platform_unpopulate_device(struct device *dev, void *c)
> > {
> >     if (!dev->of_node || !of_node_get_flag(dev->of_node, OF_POPULATED)
> >         return 0;
> > 
> >     // recursively remove the children too --- I'd like to find a way
> > to do this non-recursively
> >     device_for_each_child(dev, NULL, __of_platform_unpopulate_device);
> 
> As of_platform_populate() is recursive itself, I don't see much problem
> with this

Right, that was just a side comment. I like to avoid recursion as much
as possible in kernel code, but I'm certainly not going to NAK on that
basis.

> 
> >     // Need to check if the device should be explicitly unbound from
> > it's driver before removing it. However, I think the driver core takes
> > care of this for us.
> 
> Yep, removing either a driver or a device unbinds all existing pairs.
> 
> >     // Remove based on the bus type
> >     switch (dev->bus) {
> >         case &platform_bus_type:
> 
> To my surprise gcc said "error: pointers are not permitted as case
> values". One learns every day ;-)

:-) Good to know.

> 
> >             platform_device_remove(to_platform_device(dev));
> >             break;
> >         case &amba_bus_type:
> >             amba_device_remove(to_platform_device(dev));
> >             break;
> >     }
> > 
> >     // Should check here if there are any other children to the
> > device. It is probably bad to remove a device that still has children.
> > Need to check what the driver core will do.
> > }
> 
> The reference count will be still be greater than 0, so the parent won't
> be harmed. Nevertheless it's better to consciously handle such case. At
> least I tried.
> 
> Pawel
> 

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Re: [PATCH v3] of: Keep track of populated platform devices

[Grant Likely]

On Tue, 13 May 2014 07:24:50 -0500, Rob Herring <robherring2-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> On Tue, May 13, 2014 at 6:48 AM, Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org> wrote:
> > In "Device Tree powered" systems, platform devices are usually
> > massively populated with of_platform_populate() call, executed
> > at some level of initcalls, either by generic architecture
> > or by platform-specific code.
> >
> > There are situations though where certain devices must be
> > created (and bound with drivers) before all the others.
> > This presents a challenge, as devices created explicitly
> > would be created again by of_platform_populate().
> >
> > This patch tries to solve that issue in a generic way,
> > adding a "populated" flag for a DT node description.
> > Once set, this device will never be created again via
> > of_* API, so of_platform_populate() will skip such nodes
> > (and its children) in a similar way to the non-available
> > ones.
> >
> > The flag is cleared when a device is being removed and
> > returns the DT node by calling of_device_node_put() (it
> > was missing from the amba device release function, added).
> >
> > Signed-off-by: Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>
> 
> A few formatting nits, but otherwise:
> 
> Reviewed-by: Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>

Acked-by: Grant Likely <grant.likely-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>

g.
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Re: [PATCH v2] of: Keep track of populated platform devices

[Pawel Moll]

On Wed, 2014-05-14 at 11:56 +0100, Grant Likely wrote:
> > Agreed, but, unless I'm missing some fundamental issue, I believe we can
> > solve the flag clearing problem in a generic way:
> > 
> > --8<-----------
> > diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
> > index 3cf61a1..0f489fb 100644
> > --- a/drivers/amba/bus.c
> > +++ b/drivers/amba/bus.c
> > @@ -17,6 +17,7 @@
> >  #include <linux/pm_runtime.h>
> >  #include <linux/amba/bus.h>
> >  #include <linux/sizes.h>
> > +#include <linux/of_device.h>
> >  
> >  #include <asm/irq.h>
> >  
> > @@ -268,6 +269,7 @@ static void amba_device_release(struct device *dev)
> >  {
> >  	struct amba_device *d = to_amba_device(dev);
> >  
> > +	of_device_node_put(dev);
> >  	if (d->res.parent)
> >  		release_resource(&d->res);
> >  	kfree(d);
> > diff --git a/include/linux/of_device.h b/include/linux/of_device.h
> > index ef37021..fd14d46 100644
> > --- a/include/linux/of_device.h
> > +++ b/include/linux/of_device.h
> > @@ -41,6 +41,8 @@ extern int of_device_uevent_modalias(struct device *dev, struct kobj_uevent_env
> >  
> >  static inline void of_device_node_put(struct device *dev)
> >  {
> > +	if (dev->of_node)
> > +		of_node_clear_flag(dev->of_node, OF_POPULATED);
> >  	of_node_put(dev->of_node);
> >  }
> > --8<-----------
> > 
> > This will work even if one manually unregisters a DT-originating device,
> > because of_device_node_put() would be called in both amba and platform
> > device (kobj) release path.
> 
> Doing it that way will also catch platform_devices that were created
> apart from of_platform_populate() and manually attached to an of_node,
> which is done some times. It will also break whenever multiple devices
> reference the same node if they call of_device_node_put().
> 
> For example, a platform device providing an i2c bus will have a child
> device that represents the i2c bus, and that i2c device will point to
> the same node.

Yes, can I see it doing this. Without 

> The flag clear really does need to be kept in the
> platform_device_unpopulate path because it is only to be used internally
> by of_platform_{populate,depopulate}

Ok, will move it there.
 
> > By the way, the fact that today amba_device_release() doesn't do
> > of_device_node_put() seems like a bug to me? (node's reference counter
> > won't be decremented)
> 
> Yes, that is a bug. I want to get some unittests added to the DT code to
> verify that reference counts are being tracked correctly. Right now it
> is an utter mess.

Ok. If I move the flag, this bit is not longer an integral part of the
patch so will split it into a separate one, but merge the _depopulate()
one instead.

Thanks!

Paweł

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