This adds clk_get_optional() and devm_clk_get_optional() functions to get
optional clocks.
They behave the same as (devm_)clk_get except where there is no clock
producer. In this case, instead of returning -ENOENT, the function
returns NULL. This makes error checking simpler and allows
clk_prepare_enable, etc to be called on the returned reference
without additional checks.
Signed-off-by: Phil Edworthy <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
---
v8:
- Remove else clause
v7:
- Instead of messing with the core functions, simply wrap them for the
_optional() versions. By putting clk_get_optional() inline in the header
file, we can get rid of the arch specific patches as well.
v6:
- Add doxygen style comment for devm_clk_get_optional() args
v5:
- No changes.
v4:
- No changes.
v3:
- No changes.
---
drivers/clk/clk-devres.c | 11 +++++++++++
include/linux/clk.h | 27 +++++++++++++++++++++++++++
2 files changed, 38 insertions(+)
diff --git a/drivers/clk/clk-devres.c b/drivers/clk/clk-devres.c
index 12c87457eca1..c6f4a1a92c5f 100644
--- a/drivers/clk/clk-devres.c
+++ b/drivers/clk/clk-devres.c
@@ -34,6 +34,17 @@ struct clk *devm_clk_get(struct device *dev, const char *id)
}
EXPORT_SYMBOL(devm_clk_get);
+struct clk *devm_clk_get_optional(struct device *dev, const char *id)
+{
+ struct clk *clk = devm_clk_get(dev, id);
+
+ if (clk == ERR_PTR(-ENOENT))
+ clk = NULL;
+
+ return clk;
+}
+EXPORT_SYMBOL(devm_clk_get_optional);
+
struct clk_bulk_devres {
struct clk_bulk_data *clks;
int num_clks;
diff --git a/include/linux/clk.h b/include/linux/clk.h
index a7773b5c0b9f..3ea3c78f62dd 100644
--- a/include/linux/clk.h
+++ b/include/linux/clk.h
@@ -383,6 +383,17 @@ int __must_check devm_clk_bulk_get_all(struct device *dev,
*/
struct clk *devm_clk_get(struct device *dev, const char *id);
+/**
+ * devm_clk_get_optional - lookup and obtain a managed reference to an optional
+ * clock producer.
+ * @dev: device for clock "consumer"
+ * @id: clock consumer ID
+ *
+ * Behaves the same as devm_clk_get except where there is no clock producer. In
+ * this case, instead of returning -ENOENT, the function returns NULL.
+ */
+struct clk *devm_clk_get_optional(struct device *dev, const char *id);
+
/**
* devm_get_clk_from_child - lookup and obtain a managed reference to a
* clock producer from child node.
@@ -718,6 +729,12 @@ static inline struct clk *devm_clk_get(struct device *dev, const char *id)
return NULL;
}
+static inline struct clk *devm_clk_get_optional(struct device *dev,
+ const char *id)
+{
+ return NULL;
+}
+
static inline int __must_check devm_clk_bulk_get(struct device *dev, int num_clks,
struct clk_bulk_data *clks)
{
@@ -862,6 +879,16 @@ static inline void clk_bulk_disable_unprepare(int num_clks,
clk_bulk_unprepare(num_clks, clks);
}
+static inline struct clk *clk_get_optional(struct device *dev, const char *id)
+{
+ struct clk *clk = clk_get(dev, id);
+
+ if (clk == ERR_PTR(-ENOENT))
+ clk = NULL;
+
+ return clk;
+}
+
#if defined(CONFIG_OF) && defined(CONFIG_COMMON_CLK)
struct clk *of_clk_get(struct device_node *np, int index);
struct clk *of_clk_get_by_name(struct device_node *np, const char *name);
--
2.17.1
Quoting Phil Edworthy (2018-11-20 06:14:45)
> This adds clk_get_optional() and devm_clk_get_optional() functions to get
> optional clocks.
> They behave the same as (devm_)clk_get except where there is no clock
> producer. In this case, instead of returning -ENOENT, the function
> returns NULL. This makes error checking simpler and allows
> clk_prepare_enable, etc to be called on the returned reference
> without additional checks.
Ok. I guess that works by virtue of how -ENOENT is returned by various
functions that are called deeper in the clk_get() path? I'm cautiously
optimistic. So cautious, we should probably add a comment to these
optional functions that indicate they rely on the functions they call to
return -ENOENT under the various conditions that make a clk optional.
>
> diff --git a/include/linux/clk.h b/include/linux/clk.h
> index a7773b5c0b9f..3ea3c78f62dd 100644
> --- a/include/linux/clk.h
> +++ b/include/linux/clk.h
> @@ -383,6 +383,17 @@ int __must_check devm_clk_bulk_get_all(struct device *dev,
> */
> struct clk *devm_clk_get(struct device *dev, const char *id);
>
> +/**
> + * devm_clk_get_optional - lookup and obtain a managed reference to an optional
> + * clock producer.
> + * @dev: device for clock "consumer"
> + * @id: clock consumer ID
> + *
> + * Behaves the same as devm_clk_get except where there is no clock producer. In
Please add () around devm_clk_get() so we know it's a function.
> + * this case, instead of returning -ENOENT, the function returns NULL.
> + */
> +struct clk *devm_clk_get_optional(struct device *dev, const char *id);
> +
> /**
> * devm_get_clk_from_child - lookup and obtain a managed reference to a
> * clock producer from child node.
> @@ -718,6 +729,12 @@ static inline struct clk *devm_clk_get(struct device *dev, const char *id)
> return NULL;
> }
>
> +static inline struct clk *devm_clk_get_optional(struct device *dev,
> + const char *id)
> +{
> + return NULL;
> +}
> +
> static inline int __must_check devm_clk_bulk_get(struct device *dev, int num_clks,
> struct clk_bulk_data *clks)
> {
> @@ -862,6 +879,16 @@ static inline void clk_bulk_disable_unprepare(int num_clks,
> clk_bulk_unprepare(num_clks, clks);
> }
>
> +static inline struct clk *clk_get_optional(struct device *dev, const char *id)
Any kernel doc for this function?
> +{
> + struct clk *clk = clk_get(dev, id);
> +
> + if (clk == ERR_PTR(-ENOENT))
> + clk = NULL;
> +
> + return clk;
> +}
> +
Hi Stephen,
On 30 November 2018 09:09 Stephen Boyd wrote:
> Quoting Phil Edworthy (2018-11-20 06:14:45)
> > This adds clk_get_optional() and devm_clk_get_optional() functions to
> > get optional clocks.
> > They behave the same as (devm_)clk_get except where there is no clock
> > producer. In this case, instead of returning -ENOENT, the function
> > returns NULL. This makes error checking simpler and allows
> > clk_prepare_enable, etc to be called on the returned reference without
> > additional checks.
>
> Ok. I guess that works by virtue of how -ENOENT is returned by various
> functions that are called deeper in the clk_get() path? I'm cautiously
> optimistic. So cautious, we should probably add a comment to these optional
> functions that indicate they rely on the functions they call to return -ENOENT
> under the various conditions that make a clk optional.
Yes, it does indeed rely on how clk_get() is implemented.
Specifically, that if __of_clk_get_by_name() returns -EINVAL, the error is
superseded by clk_get_sys() returning -ENOENT.
As you say, a comment may help here.
> >
> > diff --git a/include/linux/clk.h b/include/linux/clk.h index
> > a7773b5c0b9f..3ea3c78f62dd 100644
> > --- a/include/linux/clk.h
> > +++ b/include/linux/clk.h
> > @@ -383,6 +383,17 @@ int __must_check devm_clk_bulk_get_all(struct
> device *dev,
> > */
> > struct clk *devm_clk_get(struct device *dev, const char *id);
> >
> > +/**
> > + * devm_clk_get_optional - lookup and obtain a managed reference to an
> optional
> > + * clock producer.
> > + * @dev: device for clock "consumer"
> > + * @id: clock consumer ID
> > + *
> > + * Behaves the same as devm_clk_get except where there is no clock
> > +producer. In
>
> Please add () around devm_clk_get() so we know it's a function.
Will do.
> > + * this case, instead of returning -ENOENT, the function returns NULL.
> > + */
> > +struct clk *devm_clk_get_optional(struct device *dev, const char
> > +*id);
> > +
> > /**
> > * devm_get_clk_from_child - lookup and obtain a managed reference to a
> > * clock producer from child node.
> > @@ -718,6 +729,12 @@ static inline struct clk *devm_clk_get(struct device
> *dev, const char *id)
> > return NULL;
> > }
> >
> > +static inline struct clk *devm_clk_get_optional(struct device *dev,
> > + const char *id) {
> > + return NULL;
> > +}
> > +
> > static inline int __must_check devm_clk_bulk_get(struct device *dev, int
> num_clks,
> > struct clk_bulk_data
> > *clks) { @@ -862,6 +879,16 @@ static inline void
> > clk_bulk_disable_unprepare(int num_clks,
> > clk_bulk_unprepare(num_clks, clks); }
> >
> > +static inline struct clk *clk_get_optional(struct device *dev, const
> > +char *id)
>
> Any kernel doc for this function?
I took my cue from the surrounding functions, let me know if I have to add it.
Thanks
Phil
> > +{
> > + struct clk *clk = clk_get(dev, id);
> > +
> > + if (clk == ERR_PTR(-ENOENT))
> > + clk = NULL;
> > +
> > + return clk;
> > +}
> > +
On Fri, Nov 30, 2018 at 10:25:37AM +0000, Phil Edworthy wrote:
> Hi Stephen,
>
> On 30 November 2018 09:09 Stephen Boyd wrote:
> > Quoting Phil Edworthy (2018-11-20 06:14:45)
> > > This adds clk_get_optional() and devm_clk_get_optional() functions to
> > > get optional clocks.
> > > They behave the same as (devm_)clk_get except where there is no clock
> > > producer. In this case, instead of returning -ENOENT, the function
> > > returns NULL. This makes error checking simpler and allows
> > > clk_prepare_enable, etc to be called on the returned reference without
> > > additional checks.
> >
> > Ok. I guess that works by virtue of how -ENOENT is returned by various
> > functions that are called deeper in the clk_get() path? I'm cautiously
> > optimistic. So cautious, we should probably add a comment to these optional
> > functions that indicate they rely on the functions they call to return -ENOENT
> > under the various conditions that make a clk optional.
> Yes, it does indeed rely on how clk_get() is implemented.
> Specifically, that if __of_clk_get_by_name() returns -EINVAL, the error is
> superseded by clk_get_sys() returning -ENOENT.
> As you say, a comment may help here.
Each time the question of the optional clk_get() stuff comes up, we go
around the same discussions time and time again. So far, each time
has ended up flopping.
Yes, clk_get() can only ever return -ENOENT if it falls back to the
non-DT methods, because it assumes that the clk tables are complete
(it can do nothing else.)
I don't think it needs a comment because it's obvious from the code
and also from the implementation point of view.
> > > +static inline struct clk *clk_get_optional(struct device *dev, const
> > > +char *id)
> >
> > Any kernel doc for this function?
> I took my cue from the surrounding functions, let me know if I have to add it.
I don't see you need to - this is an internal function by way of the
"static inline" you have before it. It's not an API function.
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Quoting Russell King - ARM Linux (2018-11-30 03:04:46)
> On Fri, Nov 30, 2018 at 10:25:37AM +0000, Phil Edworthy wrote:
> > On 30 November 2018 09:09 Stephen Boyd wrote:
> > > Quoting Phil Edworthy (2018-11-20 06:14:45)
> > > > This adds clk_get_optional() and devm_clk_get_optional() functions to
> > > > get optional clocks.
> > > > They behave the same as (devm_)clk_get except where there is no clock
> > > > producer. In this case, instead of returning -ENOENT, the function
> > > > returns NULL. This makes error checking simpler and allows
> > > > clk_prepare_enable, etc to be called on the returned reference without
> > > > additional checks.
> > >
> > > Ok. I guess that works by virtue of how -ENOENT is returned by various
> > > functions that are called deeper in the clk_get() path? I'm cautiously
> > > optimistic. So cautious, we should probably add a comment to these optional
> > > functions that indicate they rely on the functions they call to return -ENOENT
> > > under the various conditions that make a clk optional.
> > Yes, it does indeed rely on how clk_get() is implemented.
> > Specifically, that if __of_clk_get_by_name() returns -EINVAL, the error is
> > superseded by clk_get_sys() returning -ENOENT.
> > As you say, a comment may help here.
>
> Each time the question of the optional clk_get() stuff comes up, we go
> around the same discussions time and time again. So far, each time
> has ended up flopping.
>
> Yes, clk_get() can only ever return -ENOENT if it falls back to the
> non-DT methods, because it assumes that the clk tables are complete
> (it can do nothing else.)
>
> I don't think it needs a comment because it's obvious from the code
> and also from the implementation point of view.
Ok. I would still suggest a comment on of_clk_get_by_name() that
indicates what types of return values happen in there. Otherwise it's
obvious from the code after reading 3 or 4 functions deep
(__of_clk_get_by_name -> __of_clk_get -> of_parse_phandle_with_args and
__of_clk_get_from_provider) that this is what happens.
>
> > > > +static inline struct clk *clk_get_optional(struct device *dev, const
> > > > +char *id)
> > >
> > > Any kernel doc for this function?
> > I took my cue from the surrounding functions, let me know if I have to add it.
>
> I don't see you need to - this is an internal function by way of the
> "static inline" you have before it. It's not an API function.
It's static inline in a header file. That is an API function as far as I
can tell.