[PATCH 0/3] ARM: da8xx: fix section mismatch in new drivers

[PATCH 0/3] ARM: da8xx: fix section mismatch in new drivers

[Bartosz Golaszewski]

Sekhar noticed there's a section mismatch in the da8xx-mstpri and
da8xx-ddrctl drivers. This is caused by calling
of_flat_dt_get_machine_name() which has an __init annotation.

This series addresses this issue by introducing a new function that
allows to retrieve the compatible property of the root node and
using it instead of of_flat_dt_get_machine_name() in the new drivers.

Bartosz Golaszewski (3):
  of: base: add support to get machine compatible string
  bus: da8xx-mstpri: drop the call to of_flat_dt_get_machine_name()
  memory: da8xx-ddrctl: drop the call to of_flat_dt_get_machine_name()

 drivers/bus/da8xx-mstpri.c    |  2 +-
 drivers/memory/da8xx-ddrctl.c |  2 +-
 drivers/of/base.c             | 22 ++++++++++++++++++++++
 include/linux/of.h            |  6 ++++++
 4 files changed, 30 insertions(+), 2 deletions(-)

-- 
2.9.3

[PATCH 1/3] of: base: add support to get machine compatible string

[Bartosz Golaszewski]

Add a function allowing to retrieve the compatible string of the root
node of the device tree.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
 drivers/of/base.c  | 22 ++++++++++++++++++++++
 include/linux/of.h |  6 ++++++
 2 files changed, 28 insertions(+)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index a0bccb5..bbfe5e9 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -546,6 +546,28 @@ int of_machine_is_compatible(const char *compat)
 EXPORT_SYMBOL(of_machine_is_compatible);
 
 /**
+ * of_machine_get_compatible - Get the compatible property of the root node
+ *
+ * Returns a NULL-terminated string containing the compatible if it could
+ * be found, NULL otherwise.
+ */
+const char *of_machine_get_compatible(void)
+{
+	struct device_node *root;
+	const char *compatible;
+	int ret = -1;
+
+	root = of_find_node_by_path("/");
+	if (root) {
+		ret = of_property_read_string(root, "compatible", &compatible);
+		of_node_put(root);
+	}
+
+	return ret ? NULL : compatible;
+}
+EXPORT_SYMBOL(of_machine_get_compatible);
+
+/**
  *  __of_device_is_available - check if a device is available for use
  *
  *  @device: Node to check for availability, with locks already held
diff --git a/include/linux/of.h b/include/linux/of.h
index 299aeb1..664b734 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -367,6 +367,7 @@ extern int of_alias_get_id(struct device_node *np, const char *stem);
 extern int of_alias_get_highest_id(const char *stem);
 
 extern int of_machine_is_compatible(const char *compat);
+extern const char *of_machine_get_compatible(void);
 
 extern int of_add_property(struct device_node *np, struct property *prop);
 extern int of_remove_property(struct device_node *np, struct property *prop);
@@ -788,6 +789,11 @@ static inline int of_machine_is_compatible(const char *compat)
 	return 0;
 }
 
+static inline const char *of_machine_get_compatible(void)
+{
+	return NULL;
+}
+
 static inline bool of_console_check(const struct device_node *dn, const char *name, int index)
 {
 	return false;
-- 
2.9.3

[PATCH 1/3] of: base: add support to get machine compatible string

[Sudeep Holla]

On 22/11/16 10:41, Bartosz Golaszewski wrote:
> Add a function allowing to retrieve the compatible string of the root
> node of the device tree.
>

Rob has queued [1] and it's in -next today. You can reuse that if you
are planning to target this for v4.11 or just use open coding in your
driver for v4.10 and target this move for v4.11 to avoid cross tree
dependencies as I already mentioned in your previous thread.

-- 
Regards,
Sudeep

[1] http://www.mail-archive.com/linux-kernel at vger.kernel.org/msg1274549.html

[PATCH 1/3] of: base: add support to get machine compatible string

[Bartosz Golaszewski]

2016-11-22 11:53 GMT+01:00 Sudeep Holla <sudeep.holla@arm.com>:
>
>
> On 22/11/16 10:41, Bartosz Golaszewski wrote:
>>
>> Add a function allowing to retrieve the compatible string of the root
>> node of the device tree.
>>
>
> Rob has queued [1] and it's in -next today. You can reuse that if you
> are planning to target this for v4.11 or just use open coding in your
> driver for v4.10 and target this move for v4.11 to avoid cross tree
> dependencies as I already mentioned in your previous thread.
>
> --
> Regards,
> Sudeep
>
> [1] http://www.mail-archive.com/linux-kernel at vger.kernel.org/msg1274549.html

Rob's patch checks the model first - I'm not sure this is the behavior
we want here as Sekhar suggested we print the machine compatible.

Thanks,
Bartosz Golaszewski

[PATCH 1/3] of: base: add support to get machine compatible string

[Bartosz Golaszewski]

2016-11-22 11:57 GMT+01:00 Bartosz Golaszewski <bgolaszewski@baylibre.com>:
> 2016-11-22 11:53 GMT+01:00 Sudeep Holla <sudeep.holla@arm.com>:
>>
>>
>> On 22/11/16 10:41, Bartosz Golaszewski wrote:
>>>
>>> Add a function allowing to retrieve the compatible string of the root
>>> node of the device tree.
>>>
>>
>> Rob has queued [1] and it's in -next today. You can reuse that if you
>> are planning to target this for v4.11 or just use open coding in your
>> driver for v4.10 and target this move for v4.11 to avoid cross tree
>> dependencies as I already mentioned in your previous thread.
>>
>> --
>> Regards,
>> Sudeep
>>
>> [1] http://www.mail-archive.com/linux-kernel at vger.kernel.org/msg1274549.html
>
> Rob's patch checks the model first - I'm not sure this is the behavior
> we want here as Sekhar suggested we print the machine compatible.
>

I meant your patch of course.

Thanks,
Bartosz

[PATCH 1/3] of: base: add support to get machine compatible string

[Sudeep Holla]

On 22/11/16 10:57, Bartosz Golaszewski wrote:
> 2016-11-22 11:53 GMT+01:00 Sudeep Holla <sudeep.holla@arm.com>:
>>
>>
>> On 22/11/16 10:41, Bartosz Golaszewski wrote:
>>>
>>> Add a function allowing to retrieve the compatible string of the root
>>> node of the device tree.
>>>
>>
>> Rob has queued [1] and it's in -next today. You can reuse that if you
>> are planning to target this for v4.11 or just use open coding in your
>> driver for v4.10 and target this move for v4.11 to avoid cross tree
>> dependencies as I already mentioned in your previous thread.
>
> Rob's patch checks the model first - I'm not sure this is the behavior
> we want here as Sekhar suggested we print the machine compatible.

IIUC, you are replacing of_flat_dt_get_machine_name and
of_machine_get_model_name does exactly same. So I don't see any point in
adding this new function and it's just used for logging purpose.
Also Sekhar just gave example by using just compatible adding that
function in the driver itself.

As Arnd suggested me[1], you should for v4.10 fix it in the driver 
itself to avoid the cross tree dependencies at this point similar to [2]

--
Regards,
Sudeep

[1] 
https://www.mail-archive.com/linuxppc-dev at lists.ozlabs.org/msg111428.html
[2] http://www.mail-archive.com/linux-kernel at vger.kernel.org/msg1274502.html

[PATCH 1/3] of: base: add support to get machine compatible string

[Sekhar Nori]

On Tuesday 22 November 2016 04:36 PM, Sudeep Holla wrote:
> 
> 
> On 22/11/16 10:57, Bartosz Golaszewski wrote:
>> 2016-11-22 11:53 GMT+01:00 Sudeep Holla <sudeep.holla@arm.com>:
>>>
>>>
>>> On 22/11/16 10:41, Bartosz Golaszewski wrote:
>>>>
>>>> Add a function allowing to retrieve the compatible string of the root
>>>> node of the device tree.
>>>>
>>>
>>> Rob has queued [1] and it's in -next today. You can reuse that if you
>>> are planning to target this for v4.11 or just use open coding in your
>>> driver for v4.10 and target this move for v4.11 to avoid cross tree
>>> dependencies as I already mentioned in your previous thread.
>>
>> Rob's patch checks the model first - I'm not sure this is the behavior
>> we want here as Sekhar suggested we print the machine compatible.
> 
> IIUC, you are replacing of_flat_dt_get_machine_name and
> of_machine_get_model_name does exactly same. So I don't see any point in
> adding this new function and it's just used for logging purpose.
> Also Sekhar just gave example by using just compatible adding that
> function in the driver itself.
> 
> As Arnd suggested me[1], you should for v4.10 fix it in the driver
> itself to avoid the cross tree dependencies at this point similar to [2]

+1. Bartosz, can you please fix it in the driver for v4.10. If there is
an API available, we can move to it for v4.11

Thanks,
Sekhar

[PATCH 1/3] of: base: add support to get machine compatible string

[Sekhar Nori]

Hi Sudeep,

On Tuesday 22 November 2016 04:23 PM, Sudeep Holla wrote:
> 
> 
> On 22/11/16 10:41, Bartosz Golaszewski wrote:
>> Add a function allowing to retrieve the compatible string of the root
>> node of the device tree.
>>
> 
> Rob has queued [1] and it's in -next today. You can reuse that if you
> are planning to target this for v4.11 or just use open coding in your
> driver for v4.10 and target this move for v4.11 to avoid cross tree
> dependencies as I already mentioned in your previous thread.

I dont have your original patch in my mailbox, but I wonder if 
returning a pointer to property string for a node whose reference has 
already been released is safe to do? Probably not an issue for the root 
node, but still feels counter-intuitive.

This is the code for reference:

+int of_machine_get_model_name(const char **model)
+{
+       int error;
+
+       if (!of_node_get(of_root))
+               return -EINVAL;
+
+       error = of_property_read_string(of_root, "model", model);
+       if (error)
+               error = of_property_read_string_index(of_root, "compatible",
+                                                     0, model);
+       of_node_put(of_root);
+
+       return error;
+}
+EXPORT_SYMBOL(of_machine_get_model_name);

Thanks,
Sekhar

[PATCH 1/3] of: base: add support to get machine compatible string

[Sudeep Holla]

Hi Sekhar,

On 22/11/16 15:06, Sekhar Nori wrote:
> Hi Sudeep,
>
> On Tuesday 22 November 2016 04:23 PM, Sudeep Holla wrote:
>>
>>
>> On 22/11/16 10:41, Bartosz Golaszewski wrote:
>>> Add a function allowing to retrieve the compatible string of the root
>>> node of the device tree.
>>>
>>
>> Rob has queued [1] and it's in -next today. You can reuse that if you
>> are planning to target this for v4.11 or just use open coding in your
>> driver for v4.10 and target this move for v4.11 to avoid cross tree
>> dependencies as I already mentioned in your previous thread.
>
> I dont have your original patch in my mailbox, but I wonder if
> returning a pointer to property string for a node whose reference has
> already been released is safe to do? Probably not an issue for the root
> node, but still feels counter-intuitive.
>

I am not sure if I understand the issue here. Are you referring a case
where of_root is freed ?

Also I have seen drivers today just using this pointer directly, but
it's better to copy the string(I just saw this done in one case)

> This is the code for reference:
>
> +int of_machine_get_model_name(const char **model)
> +{
> +       int error;
> +
> +       if (!of_node_get(of_root))
> +               return -EINVAL;
> +
> +       error = of_property_read_string(of_root, "model", model);
> +       if (error)
> +               error = of_property_read_string_index(of_root, "compatible",
> +                                                     0, model);
> +       of_node_put(of_root);
> +
> +       return error;
> +}
> +EXPORT_SYMBOL(of_machine_get_model_name);
>
> Thanks,
> Sekhar
>

-- 
Regards,
Sudeep

[PATCH 1/3] of: base: add support to get machine compatible string

[Sekhar Nori]

On Tuesday 22 November 2016 09:16 PM, Sudeep Holla wrote:
> Hi Sekhar,
> 
> On 22/11/16 15:06, Sekhar Nori wrote:
>> Hi Sudeep,
>>
>> On Tuesday 22 November 2016 04:23 PM, Sudeep Holla wrote:
>>>
>>>
>>> On 22/11/16 10:41, Bartosz Golaszewski wrote:
>>>> Add a function allowing to retrieve the compatible string of the root
>>>> node of the device tree.
>>>>
>>>
>>> Rob has queued [1] and it's in -next today. You can reuse that if you
>>> are planning to target this for v4.11 or just use open coding in your
>>> driver for v4.10 and target this move for v4.11 to avoid cross tree
>>> dependencies as I already mentioned in your previous thread.
>>
>> I dont have your original patch in my mailbox, but I wonder if
>> returning a pointer to property string for a node whose reference has
>> already been released is safe to do? Probably not an issue for the root
>> node, but still feels counter-intuitive.
>>
> 
> I am not sure if I understand the issue here. Are you referring a case
> where of_root is freed ?

Yes, right, thats what I was hinting at. Since you are giving up the
reference to the device node before the function returns, the user can
be left with a dangling reference.

> Also I have seen drivers today just using this pointer directly, but
> it's better to copy the string(I just saw this done in one case)

Hmm, the reference is given up before the API returns, so I doubt
copying it later is any additional benefit.

I suspect this is a theoretical issue though since root device node is
probably never freed.

Thanks,
Sekhar

[PATCH 1/3] of: base: add support to get machine compatible string

[Sudeep Holla]

On 23/11/16 07:49, Sekhar Nori wrote:
> On Tuesday 22 November 2016 09:16 PM, Sudeep Holla wrote:
>> Hi Sekhar,
>>
>> On 22/11/16 15:06, Sekhar Nori wrote:
>>> Hi Sudeep,
>>>
>>> On Tuesday 22 November 2016 04:23 PM, Sudeep Holla wrote:
>>>>
>>>>
>>>> On 22/11/16 10:41, Bartosz Golaszewski wrote:
>>>>> Add a function allowing to retrieve the compatible string of the root
>>>>> node of the device tree.
>>>>>
>>>>
>>>> Rob has queued [1] and it's in -next today. You can reuse that if you
>>>> are planning to target this for v4.11 or just use open coding in your
>>>> driver for v4.10 and target this move for v4.11 to avoid cross tree
>>>> dependencies as I already mentioned in your previous thread.
>>>
>>> I dont have your original patch in my mailbox, but I wonder if
>>> returning a pointer to property string for a node whose reference has
>>> already been released is safe to do? Probably not an issue for the root
>>> node, but still feels counter-intuitive.
>>>
>>
>> I am not sure if I understand the issue here. Are you referring a case
>> where of_root is freed ?
>
> Yes, right, thats what I was hinting at. Since you are giving up the
> reference to the device node before the function returns, the user can
> be left with a dangling reference.
>

Yes I agree.

>> Also I have seen drivers today just using this pointer directly, but
>> it's better to copy the string(I just saw this done in one case)
>
> Hmm, the reference is given up before the API returns, so I doubt
> copying it later is any additional benefit.
>

True.

> I suspect this is a theoretical issue though since root device node is
> probably never freed.
>

Indeed, not sure if it's worth adding additional code to release the nod
at all call sites.

-- 
Regards,
Sudeep

[PATCH 1/3] of: base: add support to get machine compatible string

[Sekhar Nori]

On Wednesday 23 November 2016 03:35 PM, Sudeep Holla wrote:
> 
> 
> On 23/11/16 07:49, Sekhar Nori wrote:
>> On Tuesday 22 November 2016 09:16 PM, Sudeep Holla wrote:
>>> Hi Sekhar,
>>>
>>> On 22/11/16 15:06, Sekhar Nori wrote:
>>>> Hi Sudeep,
>>>>
>>>> On Tuesday 22 November 2016 04:23 PM, Sudeep Holla wrote:
>>>>>
>>>>>
>>>>> On 22/11/16 10:41, Bartosz Golaszewski wrote:
>>>>>> Add a function allowing to retrieve the compatible string of the root
>>>>>> node of the device tree.
>>>>>>
>>>>>
>>>>> Rob has queued [1] and it's in -next today. You can reuse that if you
>>>>> are planning to target this for v4.11 or just use open coding in your
>>>>> driver for v4.10 and target this move for v4.11 to avoid cross tree
>>>>> dependencies as I already mentioned in your previous thread.
>>>>
>>>> I dont have your original patch in my mailbox, but I wonder if
>>>> returning a pointer to property string for a node whose reference has
>>>> already been released is safe to do? Probably not an issue for the root
>>>> node, but still feels counter-intuitive.
>>>>
>>>
>>> I am not sure if I understand the issue here. Are you referring a case
>>> where of_root is freed ?
>>
>> Yes, right, thats what I was hinting at. Since you are giving up the
>> reference to the device node before the function returns, the user can
>> be left with a dangling reference.
>>
> 
> Yes I agree.

So, the if(!of_node_get()) is just an expensive NULL pointer check. I think 
it is better to be explicit about it by not using of_node_get/put() at all. 
How about:

+int of_machine_get_model_name(const char **model)
+{
+       int error;
+
+       if (!of_root)
+               return -EINVAL;
+
+       error = of_property_read_string(of_root, "model", model);
+       if (error)
+               error = of_property_read_string_index(of_root, "compatible",
+                                                     0, model);
+       return error;
+}
+EXPORT_SYMBOL(of_machine_get_model_name);

I know the patch is already in -next so I guess it depends on how strongly 
Rob feels about this.

Thanks,
Sekhar

[PATCH 1/3] of: base: add support to get machine compatible string

[Sudeep Holla]

On 23/11/16 11:47, Sekhar Nori wrote:
> On Wednesday 23 November 2016 03:35 PM, Sudeep Holla wrote:
>>
>>
>> On 23/11/16 07:49, Sekhar Nori wrote:
>>> On Tuesday 22 November 2016 09:16 PM, Sudeep Holla wrote:
>>>> Hi Sekhar,
>>>>
>>>> On 22/11/16 15:06, Sekhar Nori wrote:
>>>>> Hi Sudeep,
>>>>>
>>>>> On Tuesday 22 November 2016 04:23 PM, Sudeep Holla wrote:
>>>>>>
>>>>>>
>>>>>> On 22/11/16 10:41, Bartosz Golaszewski wrote:
>>>>>>> Add a function allowing to retrieve the compatible string of the root
>>>>>>> node of the device tree.
>>>>>>>
>>>>>>
>>>>>> Rob has queued [1] and it's in -next today. You can reuse that if you
>>>>>> are planning to target this for v4.11 or just use open coding in your
>>>>>> driver for v4.10 and target this move for v4.11 to avoid cross tree
>>>>>> dependencies as I already mentioned in your previous thread.
>>>>>
>>>>> I dont have your original patch in my mailbox, but I wonder if
>>>>> returning a pointer to property string for a node whose reference has
>>>>> already been released is safe to do? Probably not an issue for the root
>>>>> node, but still feels counter-intuitive.
>>>>>
>>>>
>>>> I am not sure if I understand the issue here. Are you referring a case
>>>> where of_root is freed ?
>>>
>>> Yes, right, thats what I was hinting at. Since you are giving up the
>>> reference to the device node before the function returns, the user can
>>> be left with a dangling reference.
>>>
>>
>> Yes I agree.
>
> So, the if(!of_node_get()) is just an expensive NULL pointer check. I think
> it is better to be explicit about it by not using of_node_get/put() at all.
> How about:
>

Are we planning to use this in any time sensitive paths? Anyways I am
fine removing them.

> +int of_machine_get_model_name(const char **model)
> +{
> +       int error;
> +
> +       if (!of_root)
> +               return -EINVAL;
> +
> +       error = of_property_read_string(of_root, "model", model);
> +       if (error)
> +               error = of_property_read_string_index(of_root, "compatible",
> +                                                     0, model);
> +       return error;
> +}
> +EXPORT_SYMBOL(of_machine_get_model_name);
>
> I know the patch is already in -next so I guess it depends on how strongly
> Rob feels about this.

Frank expressed his concerns and it may be reverted.

-- 
Regards,
Sudeep

[PATCH 1/3] of: base: add support to get machine compatible string

[Sekhar Nori]

On Wednesday 23 November 2016 05:37 PM, Sudeep Holla wrote:
>> So, the if(!of_node_get()) is just an expensive NULL pointer check. I
>> think
>> it is better to be explicit about it by not using of_node_get/put() at
>> all.
>> How about:
>>
> 
> Are we planning to use this in any time sensitive paths? Anyways I am
> fine removing them.

Not worried about the time taken as much as it serving as a bad example
and getting carried over to other places where the impact might actually
be real.

> 
>> +int of_machine_get_model_name(const char **model)
>> +{
>> +       int error;
>> +
>> +       if (!of_root)
>> +               return -EINVAL;
>> +
>> +       error = of_property_read_string(of_root, "model", model);
>> +       if (error)
>> +               error = of_property_read_string_index(of_root,
>> "compatible",
>> +                                                     0, model);
>> +       return error;
>> +}
>> +EXPORT_SYMBOL(of_machine_get_model_name);
>>
>> I know the patch is already in -next so I guess it depends on how
>> strongly
>> Rob feels about this.
> 
> Frank expressed his concerns and it may be reverted.

Didn't notice that. I will check that thread. Thanks!

Regards,
Sekhar

[PATCH 1/3] of: base: add support to get machine compatible string

[Sudeep Holla]

On 23/11/16 12:13, Sekhar Nori wrote:
> On Wednesday 23 November 2016 05:37 PM, Sudeep Holla wrote:
>>> So, the if(!of_node_get()) is just an expensive NULL pointer check. I
>>> think
>>> it is better to be explicit about it by not using of_node_get/put() at
>>> all.
>>> How about:
>>>
>>
>> Are we planning to use this in any time sensitive paths? Anyways I am
>> fine removing them.
>
> Not worried about the time taken as much as it serving as a bad example
> and getting carried over to other places where the impact might actually
> be real.
>

Ah OK, sure.

-- 
Regards,
Sudeep

[PATCH 2/3] bus: da8xx-mstpri: drop the call to of_flat_dt_get_machine_name()

[Bartosz Golaszewski]

In order to avoid a section mismatch use of_machine_get_compatible()
instead of of_flat_dt_get_machine_name() when printing the error
message.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
 drivers/bus/da8xx-mstpri.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/bus/da8xx-mstpri.c b/drivers/bus/da8xx-mstpri.c
index 85f0b53..41cbbe6 100644
--- a/drivers/bus/da8xx-mstpri.c
+++ b/drivers/bus/da8xx-mstpri.c
@@ -227,7 +227,7 @@ static int da8xx_mstpri_probe(struct platform_device *pdev)
 	prio_list = da8xx_mstpri_get_board_prio();
 	if (!prio_list) {
 		dev_err(dev, "no master priotities defined for board '%s'\n",
-			of_flat_dt_get_machine_name());
+			of_machine_get_compatible());
 		return -EINVAL;
 	}
 
-- 
2.9.3

[PATCH 3/3] memory: da8xx-ddrctl: drop the call to of_flat_dt_get_machine_name()

[Bartosz Golaszewski]

In order to avoid a section mismatch use of_machine_get_compatible()
instead of of_flat_dt_get_machine_name() when printing the error
message.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
 drivers/memory/da8xx-ddrctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/memory/da8xx-ddrctl.c b/drivers/memory/da8xx-ddrctl.c
index a20e7bb..179f505 100644
--- a/drivers/memory/da8xx-ddrctl.c
+++ b/drivers/memory/da8xx-ddrctl.c
@@ -118,7 +118,7 @@ static int da8xx_ddrctl_probe(struct platform_device *pdev)
 	setting = da8xx_ddrctl_get_board_settings();
 	if (!setting) {
 		dev_err(dev, "no settings for board '%s'\n",
-			of_flat_dt_get_machine_name());
+			of_machine_get_compatible());
 		return -EINVAL;
 	}
 
-- 
2.9.3