of: Add of_get_memory_prop()
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Message ID 20190918184656.7633-1-rananta@codeaurora.org
State Changes Requested
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  • of: Add of_get_memory_prop()
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Commit Message

Raghavendra Rao Ananta Sept. 18, 2019, 6:46 p.m. UTC
On some embedded systems, the '/memory' dt-property gets updated
by the bootloader (for example, the DDR configuration) and then
gets passed onto the kernel. The device drivers may have to read
the properties at runtime to make decisions. Hence, add
of_get_memory_prop() for the device drivers to query the requested
properties.

Signed-off-by: Raghavendra Rao Ananta <rananta@codeaurora.org>
---
 drivers/of/fdt.c       | 27 +++++++++++++++++++++++++++
 include/linux/of_fdt.h |  1 +
 2 files changed, 28 insertions(+)

Comments

Rob Herring Sept. 18, 2019, 8:13 p.m. UTC | #1
On Wed, Sep 18, 2019 at 1:47 PM Raghavendra Rao Ananta
<rananta@codeaurora.org> wrote:
>
> On some embedded systems, the '/memory' dt-property gets updated
> by the bootloader (for example, the DDR configuration) and then
> gets passed onto the kernel. The device drivers may have to read
> the properties at runtime to make decisions. Hence, add
> of_get_memory_prop() for the device drivers to query the requested

Function name doesn't match. Device drivers don't need to access the FDT.

> properties.
>
> Signed-off-by: Raghavendra Rao Ananta <rananta@codeaurora.org>
> ---
>  drivers/of/fdt.c       | 27 +++++++++++++++++++++++++++
>  include/linux/of_fdt.h |  1 +
>  2 files changed, 28 insertions(+)

We don't add kernel api's without users.

>
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index 223d617ecfe1..925cf2852433 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -79,6 +79,33 @@ void __init of_fdt_limit_memory(int limit)
>         }
>  }
>
> +/**
> + * of_fdt_get_memory_prop - Return the requested property from the /memory node
> + *
> + * On match, returns a non-zero positive value which represents the property
> + * value. Otherwise returns -ENOENT.
> + */
> +int of_fdt_get_memory_prop(const char *pname)
> +{
> +       int memory;
> +       int len;
> +       fdt32_t *prop = NULL;
> +
> +       if (!pname)
> +               return -EINVAL;
> +
> +       memory = fdt_path_offset(initial_boot_params, "/memory");

Memory nodes should have a unit-address, so this won't work frequently.

> +       if (memory > 0)
> +               prop = fdt_getprop_w(initial_boot_params, memory,
> +                                 pname, &len);
> +
> +       if (!prop || len != sizeof(u32))
> +               return -ENOENT;
> +
> +       return fdt32_to_cpu(*prop);
> +}
> +EXPORT_SYMBOL_GPL(of_fdt_get_memory_prop);
> +
>  static bool of_fdt_device_is_available(const void *blob, unsigned long node)
>  {
>         const char *status = fdt_getprop(blob, node, "status", NULL);
> diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
> index acf820e88952..537f29373358 100644
> --- a/include/linux/of_fdt.h
> +++ b/include/linux/of_fdt.h
> @@ -38,6 +38,7 @@ extern char __dtb_end[];
>  /* Other Prototypes */
>  extern u64 of_flat_dt_translate_address(unsigned long node);
>  extern void of_fdt_limit_memory(int limit);
> +extern int of_fdt_get_memory_prop(const char *pname);
>  #endif /* CONFIG_OF_FLATTREE */
>
>  #ifdef CONFIG_OF_EARLY_FLATTREE
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>
Raghavendra Rao Ananta Sept. 18, 2019, 10:32 p.m. UTC | #2
On 2019-09-18 13:13, Rob Herring wrote:
> On Wed, Sep 18, 2019 at 1:47 PM Raghavendra Rao Ananta
> <rananta@codeaurora.org> wrote:
>> 
>> On some embedded systems, the '/memory' dt-property gets updated
>> by the bootloader (for example, the DDR configuration) and then
>> gets passed onto the kernel. The device drivers may have to read
>> the properties at runtime to make decisions. Hence, add
>> of_get_memory_prop() for the device drivers to query the requested
> 
> Function name doesn't match. Device drivers don't need to access the 
> FDT.
> 
>> properties.
>> 
>> Signed-off-by: Raghavendra Rao Ananta <rananta@codeaurora.org>
>> ---
>>  drivers/of/fdt.c       | 27 +++++++++++++++++++++++++++
>>  include/linux/of_fdt.h |  1 +
>>  2 files changed, 28 insertions(+)
> 
> We don't add kernel api's without users.
> 
>> 
>> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
>> index 223d617ecfe1..925cf2852433 100644
>> --- a/drivers/of/fdt.c
>> +++ b/drivers/of/fdt.c
>> @@ -79,6 +79,33 @@ void __init of_fdt_limit_memory(int limit)
>>         }
>>  }
>> 
>> +/**
>> + * of_fdt_get_memory_prop - Return the requested property from the 
>> /memory node
>> + *
>> + * On match, returns a non-zero positive value which represents the 
>> property
>> + * value. Otherwise returns -ENOENT.
>> + */
>> +int of_fdt_get_memory_prop(const char *pname)
>> +{
>> +       int memory;
>> +       int len;
>> +       fdt32_t *prop = NULL;
>> +
>> +       if (!pname)
>> +               return -EINVAL;
>> +
>> +       memory = fdt_path_offset(initial_boot_params, "/memory");
> 
> Memory nodes should have a unit-address, so this won't work frequently.
Sorry, can you please elaborate more on this? What do you mean by 
unit-address and working frequently?
> 
>> +       if (memory > 0)
>> +               prop = fdt_getprop_w(initial_boot_params, memory,
>> +                                 pname, &len);
>> +
>> +       if (!prop || len != sizeof(u32))
>> +               return -ENOENT;
>> +
>> +       return fdt32_to_cpu(*prop);
>> +}
>> +EXPORT_SYMBOL_GPL(of_fdt_get_memory_prop);
>> +
>>  static bool of_fdt_device_is_available(const void *blob, unsigned 
>> long node)
>>  {
>>         const char *status = fdt_getprop(blob, node, "status", NULL);
>> diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
>> index acf820e88952..537f29373358 100644
>> --- a/include/linux/of_fdt.h
>> +++ b/include/linux/of_fdt.h
>> @@ -38,6 +38,7 @@ extern char __dtb_end[];
>>  /* Other Prototypes */
>>  extern u64 of_flat_dt_translate_address(unsigned long node);
>>  extern void of_fdt_limit_memory(int limit);
>> +extern int of_fdt_get_memory_prop(const char *pname);
>>  #endif /* CONFIG_OF_FLATTREE */
>> 
>>  #ifdef CONFIG_OF_EARLY_FLATTREE
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
>> Forum,
>> a Linux Foundation Collaborative Project
>> 
- Raghavendra
Rob Herring Oct. 1, 2019, 10:09 p.m. UTC | #3
On Wed, Sep 18, 2019 at 03:32:14PM -0700, rananta@codeaurora.org wrote:
> On 2019-09-18 13:13, Rob Herring wrote:
> > On Wed, Sep 18, 2019 at 1:47 PM Raghavendra Rao Ananta
> > <rananta@codeaurora.org> wrote:
> > > 
> > > On some embedded systems, the '/memory' dt-property gets updated
> > > by the bootloader (for example, the DDR configuration) and then
> > > gets passed onto the kernel. The device drivers may have to read
> > > the properties at runtime to make decisions. Hence, add
> > > of_get_memory_prop() for the device drivers to query the requested
> > 
> > Function name doesn't match. Device drivers don't need to access the
> > FDT.
> > 
> > > properties.
> > > 
> > > Signed-off-by: Raghavendra Rao Ananta <rananta@codeaurora.org>
> > > ---
> > >  drivers/of/fdt.c       | 27 +++++++++++++++++++++++++++
> > >  include/linux/of_fdt.h |  1 +
> > >  2 files changed, 28 insertions(+)
> > 
> > We don't add kernel api's without users.
> > 
> > > 
> > > diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> > > index 223d617ecfe1..925cf2852433 100644
> > > --- a/drivers/of/fdt.c
> > > +++ b/drivers/of/fdt.c
> > > @@ -79,6 +79,33 @@ void __init of_fdt_limit_memory(int limit)
> > >         }
> > >  }
> > > 
> > > +/**
> > > + * of_fdt_get_memory_prop - Return the requested property from the
> > > /memory node
> > > + *
> > > + * On match, returns a non-zero positive value which represents the
> > > property
> > > + * value. Otherwise returns -ENOENT.
> > > + */
> > > +int of_fdt_get_memory_prop(const char *pname)
> > > +{
> > > +       int memory;
> > > +       int len;
> > > +       fdt32_t *prop = NULL;
> > > +
> > > +       if (!pname)
> > > +               return -EINVAL;
> > > +
> > > +       memory = fdt_path_offset(initial_boot_params, "/memory");
> > 
> > Memory nodes should have a unit-address, so this won't work frequently.
> Sorry, can you please elaborate more on this? What do you mean by
> unit-address and working frequently?

A memory node is typically going to be something like: /memory@80000000. 
So your function will not work for any of those cases. And just 
'/memory' generates a dtc warning.

Rob
Frank Rowand Oct. 17, 2019, 6:35 p.m. UTC | #4
Hi Raghavendra,

I have not received your emails in this conversation, and I do not see
them in my spam folder.  I see some replies from Rob, so I am guessing
he added me to the CC: list.

Please add me to future Devicetree emails.

Digging a little deeper, in the devicetree mail list archive, I see
myself on the CC: list of your "Date: Wed, 18 Sep 2019 15:32:14 -0700"
reply to Rob.  I'm not sure why that email did not get through to me.

So just a heads up that something may be interfering with delivery of email
from you to me.  I've seen disappearing email problem from other senders,
even when most of their emails get through.

Thanks,

Frank


On 10/01/2019 17:09, Rob Herring wrote:
> On Wed, Sep 18, 2019 at 03:32:14PM -0700, rananta@codeaurora.org wrote:
>> On 2019-09-18 13:13, Rob Herring wrote:
>>> On Wed, Sep 18, 2019 at 1:47 PM Raghavendra Rao Ananta
>>> <rananta@codeaurora.org> wrote:
>>>>
>>>> On some embedded systems, the '/memory' dt-property gets updated
>>>> by the bootloader (for example, the DDR configuration) and then
>>>> gets passed onto the kernel. The device drivers may have to read
>>>> the properties at runtime to make decisions. Hence, add
>>>> of_get_memory_prop() for the device drivers to query the requested
>>>
>>> Function name doesn't match. Device drivers don't need to access the
>>> FDT.
>>>
>>>> properties.
>>>>
>>>> Signed-off-by: Raghavendra Rao Ananta <rananta@codeaurora.org>
>>>> ---
>>>>  drivers/of/fdt.c       | 27 +++++++++++++++++++++++++++
>>>>  include/linux/of_fdt.h |  1 +
>>>>  2 files changed, 28 insertions(+)
>>>
>>> We don't add kernel api's without users.
>>>
>>>>
>>>> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
>>>> index 223d617ecfe1..925cf2852433 100644
>>>> --- a/drivers/of/fdt.c
>>>> +++ b/drivers/of/fdt.c
>>>> @@ -79,6 +79,33 @@ void __init of_fdt_limit_memory(int limit)
>>>>         }
>>>>  }
>>>>
>>>> +/**
>>>> + * of_fdt_get_memory_prop - Return the requested property from the
>>>> /memory node
>>>> + *
>>>> + * On match, returns a non-zero positive value which represents the
>>>> property
>>>> + * value. Otherwise returns -ENOENT.
>>>> + */
>>>> +int of_fdt_get_memory_prop(const char *pname)
>>>> +{
>>>> +       int memory;
>>>> +       int len;
>>>> +       fdt32_t *prop = NULL;
>>>> +
>>>> +       if (!pname)
>>>> +               return -EINVAL;
>>>> +
>>>> +       memory = fdt_path_offset(initial_boot_params, "/memory");
>>>
>>> Memory nodes should have a unit-address, so this won't work frequently.
>> Sorry, can you please elaborate more on this? What do you mean by
>> unit-address and working frequently?
> 
> A memory node is typically going to be something like: /memory@80000000. 
> So your function will not work for any of those cases. And just 
> '/memory' generates a dtc warning.
> 
> Rob
> 
>

Patch
diff mbox series

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 223d617ecfe1..925cf2852433 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -79,6 +79,33 @@  void __init of_fdt_limit_memory(int limit)
 	}
 }
 
+/**
+ * of_fdt_get_memory_prop - Return the requested property from the /memory node
+ *
+ * On match, returns a non-zero positive value which represents the property
+ * value. Otherwise returns -ENOENT.
+ */
+int of_fdt_get_memory_prop(const char *pname)
+{
+	int memory;
+	int len;
+	fdt32_t *prop = NULL;
+
+	if (!pname)
+		return -EINVAL;
+
+	memory = fdt_path_offset(initial_boot_params, "/memory");
+	if (memory > 0)
+		prop = fdt_getprop_w(initial_boot_params, memory,
+				  pname, &len);
+
+	if (!prop || len != sizeof(u32))
+		return -ENOENT;
+
+	return fdt32_to_cpu(*prop);
+}
+EXPORT_SYMBOL_GPL(of_fdt_get_memory_prop);
+
 static bool of_fdt_device_is_available(const void *blob, unsigned long node)
 {
 	const char *status = fdt_getprop(blob, node, "status", NULL);
diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
index acf820e88952..537f29373358 100644
--- a/include/linux/of_fdt.h
+++ b/include/linux/of_fdt.h
@@ -38,6 +38,7 @@  extern char __dtb_end[];
 /* Other Prototypes */
 extern u64 of_flat_dt_translate_address(unsigned long node);
 extern void of_fdt_limit_memory(int limit);
+extern int of_fdt_get_memory_prop(const char *pname);
 #endif /* CONFIG_OF_FLATTREE */
 
 #ifdef CONFIG_OF_EARLY_FLATTREE