Re: [PATCH v20 2/6] phy: core: Add phy_get_by_of_node()

[johannes . goede]

Hi Neil,

On 18-Sep-26 16:10, Neil Armstrong wrote:
> On 9/18/26 15:56, Bryan O'Donoghue wrote:
>> Add new function phy_get_by_of_node() allowing lookup of a phy by
>> device_node. Separates existing logic in _of_phy_get() into an internal
>> helper method _of_phy_get_with_args() to allow for reuse in new method.
>>
>> Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@xxxxxxxxxx>
>> ---
>>   drivers/phy/phy-core.c  | 83 ++++++++++++++++++++++++++++++++++++++-----------
>>   include/linux/phy/phy.h |  6 ++++
>>   2 files changed, 71 insertions(+), 18 deletions(-)
>>
>> diff --git a/drivers/phy/phy-core.c b/drivers/phy/phy-core.c
>> index 89addd732bff3..42c27a2b45159 100644
>> --- a/drivers/phy/phy-core.c
>> +++ b/drivers/phy/phy-core.c
>> @@ -606,6 +606,38 @@ int phy_validate(struct phy *phy, enum phy_mode mode, int submode,
>>   }
>>   EXPORT_SYMBOL_GPL(phy_validate);
>>   +/**
>> + * _of_phy_get_with_args() - lookup and obtain a reference to a phy by of_phandle_args
>> + * @args: of_phandle_args to the phy
>> + *
>> + * Returns: the phy from the provider's of_xlate, -ENODEV if disabled,
>> + * -EPROBE_DEFER if the provider is not yet registered.
>> + */
>> +static struct phy *_of_phy_get_with_args(struct of_phandle_args *args)
>> +{
>> +    struct phy *phy;
>> +    struct phy_provider *phy_provider;
>> +
>> +    lockdep_assert_held(&phy_provider_mutex);
>> +
>> +    phy_provider = of_phy_provider_lookup(args->np);
>> +    if (IS_ERR(phy_provider) || !try_module_get(phy_provider->owner))
>> +        return ERR_PTR(-EPROBE_DEFER);
>> +
>> +    if (!of_device_is_available(args->np)) {
>> +        dev_warn(phy_provider->dev, "Requested PHY is disabled\n");
>> +        phy = ERR_PTR(-ENODEV);
>> +        goto out_put_module;
>> +    }
>> +
>> +    phy = phy_provider->of_xlate(phy_provider->dev, args);
>> +
>> +out_put_module:
>> +    module_put(phy_provider->owner);
>> +
>> +    return phy;
>> +}
>> +
>>   /**
>>    * _of_phy_get() - lookup and obtain a reference to a phy by phandle
>>    * @np: device_node for which to get the phy
>> @@ -620,8 +652,7 @@ EXPORT_SYMBOL_GPL(phy_validate);
>>   static struct phy *_of_phy_get(struct device_node *np, int index)
>>   {
>>       int ret;
>> -    struct phy_provider *phy_provider;
>> -    struct phy *phy = NULL;
>> +    struct phy *phy;
>>       struct of_phandle_args args;
>>         lockdep_assert_held(&phy_provider_mutex);
>> @@ -637,22 +668,7 @@ static struct phy *_of_phy_get(struct device_node *np, int index)
>>           goto out_put_node;
>>       }
>>   -    phy_provider = of_phy_provider_lookup(args.np);
>> -    if (IS_ERR(phy_provider) || !try_module_get(phy_provider->owner)) {
>> -        phy = ERR_PTR(-EPROBE_DEFER);
>> -        goto out_put_node;
>> -    }
>> -
>> -    if (!of_device_is_available(args.np)) {
>> -        dev_warn(phy_provider->dev, "Requested PHY is disabled\n");
>> -        phy = ERR_PTR(-ENODEV);
>> -        goto out_put_module;
>> -    }
>> -
>> -    phy = phy_provider->of_xlate(phy_provider->dev, &args);
>> -
>> -out_put_module:
>> -    module_put(phy_provider->owner);
>> +    phy = _of_phy_get_with_args(&args);
>>     out_put_node:
>>       of_node_put(args.np);
>> @@ -1001,6 +1017,37 @@ struct phy *devm_of_phy_get_by_index(struct device *dev, struct device_node *np,
>>   }
>>   EXPORT_SYMBOL_GPL(devm_of_phy_get_by_index);
>>   +/**
>> + * phy_get_by_of_node() - lookup and obtain a reference to a phy by device_node
>> + * @np: node containing the phy
>> + *
>> + * Returns: the phy associated with the device node or ERR_PTR.
>> + */
>> +struct phy *phy_get_by_of_node(struct device_node *np)
>> +{
>> +    struct of_phandle_args args = { .np = np, .args_count = 0 };
>> +    struct phy *phy;
>> +
>> +    mutex_lock(&phy_provider_mutex);
> 
> I don't really understand the usage of lockdep_assert_held(), but why
> does _of_phy_get() uses lockdep_assert_held() and here you use mutex_lock()
> like before patch 1 ?

Hi, not Bryan but I can answer this question.

lockdep_assert_held() check that the mutex is lock and triggers
a WARN() when not held.

So lockdep_assert_held() is used in functions which expect to
be called with the mutex already locked, like the new
_of_phy_get_with_args() helper which is added here.

This new helper factors out bits of _of_phy_get(), which itself
already has lockdep_assert_held(), but since this new helper
also is directly called from the new phy_get_by_of_node() it
is good for it to also check the mutex is locked itself.

And since the new phy_get_by_of_node() calls this new helper
it must lock the mutex.

Note that _of_phy_get() is already always called with the mutex
locked from of_phy_get(), phy_get(), or devm_of_phy_get_by_index().

Regards,

Hans




> 
> Neil
> 
>> +
>> +    phy = _of_phy_get_with_args(&args);
>> +    if (IS_ERR(phy))
>> +        goto out_unlock;
>> +
>> +    if (!try_module_get(phy->ops->owner)) {
>> +        phy = ERR_PTR(-EPROBE_DEFER);
>> +        goto out_unlock;
>> +    }
>> +
>> +    get_device(&phy->dev);
>> +
>> +out_unlock:
>> +    mutex_unlock(&phy_provider_mutex);
>> +
>> +    return phy;
>> +}
>> +EXPORT_SYMBOL_GPL(phy_get_by_of_node);
>> +
>>   /**
>>    * phy_create() - create a new phy
>>    * @dev: device that is creating the new phy
>> diff --git a/include/linux/phy/phy.h b/include/linux/phy/phy.h
>> index ea47975e288ae..71c2e16397130 100644
>> --- a/include/linux/phy/phy.h
>> +++ b/include/linux/phy/phy.h
>> @@ -284,6 +284,7 @@ struct phy *devm_of_phy_optional_get(struct device *dev, struct device_node *np,
>>                        const char *con_id);
>>   struct phy *devm_of_phy_get_by_index(struct device *dev, struct device_node *np,
>>                        int index);
>> +struct phy *phy_get_by_of_node(struct device_node *np);
>>   void of_phy_put(struct phy *phy);
>>   void phy_put(struct device *dev, struct phy *phy);
>>   void devm_phy_put(struct device *dev, struct phy *phy);
>> @@ -493,6 +494,11 @@ static inline struct phy *devm_of_phy_get_by_index(struct device *dev,
>>       return ERR_PTR(-ENOSYS);
>>   }
>>   +static inline struct phy *phy_get_by_of_node(struct device_node *np)
>> +{
>> +    return ERR_PTR(-ENOSYS);
>> +}
>> +
>>   static inline void of_phy_put(struct phy *phy)
>>   {
>>   }
>>
> 
>