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Subject: Re: [PATCH 02/11] mux: core: Add support for getting a mux controller
 on a non DT platform
To: Peter Rosin <peda@axentia.se>, MyungJoo Ham <myungjoo.ham@samsung.com>,
        Chanwoo Choi <cw00.choi@samsung.com>,
        Guenter Roeck <linux@roeck-us.net>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        Darren Hart <dvhart@infradead.org>,
        Andy Shevchenko <andy@infradead.org>,
        Mathias Nyman <mathias.nyman@intel.com>
Cc: platform-driver-x86@vger.kernel.org, devel@driverdev.osuosl.org,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        Sathyanarayanan Kuppuswamy Natarajan <sathyaosid@gmail.com>,
        linux-kernel@vger.kernel.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-usb@vger.kernel.org
References: <20170901214845.7153-1-hdegoede@redhat.com>
 <20170901214845.7153-3-hdegoede@redhat.com>
 <0c882d23-d008-3d61-27be-3fa22bf59521@axentia.se>
From: Hans de Goede <hdegoede@redhat.com>
Message-ID: <1e457bb5-a493-fb13-0dd2-efa0b019a8d2@redhat.com>
Date: Tue, 5 Sep 2017 12:58:12 +0200
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Hi,

On 04-09-17 13:19, Peter Rosin wrote:
> Hi!
> 
> Some comments inline...
> 
> On 2017-09-01 23:48, Hans de Goede wrote:
>> On non DT platforms we cannot get the mux_chip by pnode. Other subsystems
>> (regulator, clock, pwm) have the same problem and solve this by allowing
>> platform / board-setup code to add entries to a lookup table and then use
>> this table to look things up.
>>
>> This commit adds support for getting a mux controller on a non DT platform
>> following this pattern. It is based on a simplified version of the pwm
>> subsys lookup code, the dev_id and mux_name parts of a lookup table entry
>> are mandatory in the mux-core implementation.
>>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>>   drivers/mux/core.c           | 96 +++++++++++++++++++++++++++++++++++++++++++-
>>   include/linux/mux/consumer.h | 11 +++++
>>   2 files changed, 106 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mux/core.c b/drivers/mux/core.c
>> index 6142493c327b..8864cc745506 100644
>> --- a/drivers/mux/core.c
>> +++ b/drivers/mux/core.c
>> @@ -24,6 +24,9 @@
>>   #include <linux/of_platform.h>
>>   #include <linux/slab.h>
>>   
>> +static DEFINE_MUTEX(mux_lookup_lock);
>> +static LIST_HEAD(mux_lookup_list);
>> +
>>   /*
>>    * The idle-as-is "state" is not an actual state that may be selected, it
>>    * only implies that the state should not be changed. So, use that state
>> @@ -408,6 +411,23 @@ int mux_control_deselect(struct mux_control *mux)
>>   }
>>   EXPORT_SYMBOL_GPL(mux_control_deselect);
>>   
>> +static int parent_name_match(struct device *dev, const void *data)
>> +{
>> +	const char *parent_name = dev_name(dev->parent);
>> +	const char *name = data;
>> +
>> +	return strcmp(parent_name, name) == 0;
>> +}
>> +
>> +static struct mux_chip *mux_chip_get_by_name(const char *name)
>> +{
>> +	struct device *dev;
>> +
>> +	dev = class_find_device(&mux_class, NULL, name, parent_name_match);
>> +
>> +	return dev ? to_mux_chip(dev) : NULL;
>> +}
>> +
>>   static int of_dev_node_match(struct device *dev, const void *data)
>>   {
>>   	return dev->of_node == data;
>> @@ -479,6 +499,42 @@ static struct mux_control *of_mux_control_get(struct device *dev,
>>   }
>>   
>>   /**
>> + * mux_add_table() - register PWM device consumers
> 
> register mux controllers (because you are not registering consumers, right?
> someone is registering controllers so that they can be found by consumers?)


Actually what is being registered is a "consumer to mux-controller mapping",
I will update the kernel-doc comments to use that everywhere.

> 
>> + * @table: array of consumers to register
>> + * @num: number of consumers in table
> 
> controllers?

mappings :)

>> + */
>> +void mux_add_table(struct mux_lookup *table, size_t num)
>> +{
>> +	mutex_lock(&mux_lookup_lock);
>> +
>> +	while (num--) {
>> +		list_add_tail(&table->list, &mux_lookup_list);
>> +		table++;
>> +	}
> 
> I prefer
> 
> 	for (; num--; table++)
> 		list_add_tail(&table->list, &mux_lookup_list);

Sure, works for me.

>> +
>> +	mutex_unlock(&mux_lookup_lock);
>> +}
>> +EXPORT_SYMBOL_GPL(mux_add_table);
>> +
>> +/**
>> + * mux_remove_table() - unregister PWM device consumers
> 
> unregister mux controllers(?)
> 
>> + * @table: array of consumers to unregister
>> + * @num: number of consumers in table
> 
> controllers?
> 
>> + */
>> +void mux_remove_table(struct mux_lookup *table, size_t num)
>> +{
>> +	mutex_lock(&mux_lookup_lock);
>> +
>> +	while (num--) {
>> +		list_del(&table->list);
>> +		table++;
>> +	}
> 
> for() loop here as well.

Ack.

>> +
>> +	mutex_unlock(&mux_lookup_lock);
>> +}
>> +EXPORT_SYMBOL_GPL(mux_remove_table);
>> +
>> +/**
>>    * mux_control_get() - Get the mux-control for a device.
>>    * @dev: The device that needs a mux-control.
>>    * @mux_name: The name identifying the mux-control.
>> @@ -487,11 +543,49 @@ static struct mux_control *of_mux_control_get(struct device *dev,
>>    */
>>   struct mux_control *mux_control_get(struct device *dev, const char *mux_name)
>>   {
>> +	struct mux_lookup *m, *chosen = NULL;
>> +	const char *dev_id = dev_name(dev);
>> +	struct mux_chip *mux_chip;
>> +
>>   	/* look up via DT first */
>>   	if (IS_ENABLED(CONFIG_OF) && dev->of_node)
>>   		return of_mux_control_get(dev, mux_name);
>>   
>> -	return ERR_PTR(-ENODEV);
>> +	/*
>> +	 * For non DT we look up the provider in the static table typically
>> +	 * provided by board setup code.
>> +	 *
>> +	 * If a match is found, the provider mux chip is looked up by name
>> +	 * and a mux-control is requested using the table provided index.
>> +	 */
>> +	mutex_lock(&mux_lookup_lock);
>> +	list_for_each_entry(m, &mux_lookup_list, list) {
>> +		if (WARN_ON(!m->dev_id || !m->mux_name || !m->provider))
>> +			continue;
>> +
>> +		if (strcmp(m->dev_id, dev_id) == 0 &&
>> +		    strcmp(m->mux_name, mux_name) == 0) {
> 
> I want the below format (with ! instead of == 0 and the brace on the next line
> when the condition has a line break):

Ok, I think checkpatch is going to not like that "{" there, but
I'm fine with putting it there.

> 		if (!strcmp(m->dev_id, dev_id) &&
> 		    !strcmp(m->mux_name, mux_name))
> 		{
> 
>> +			chosen = m;
>> +			break;
>> +		}
>> +	}
>> +	mutex_unlock(&mux_lookup_lock);
>> +
>> +	if (!chosen)
>> +		return ERR_PTR(-ENODEV);
>> +
>> +	mux_chip = mux_chip_get_by_name(chosen->provider);
>> +	if (!mux_chip)
>> +		return ERR_PTR(-EPROBE_DEFER);
>> +
>> +	if (chosen->index >= mux_chip->controllers) {
>> +		dev_err(dev, "Mux lookup table index out of bounds %u >= %u\n",
>> +			chosen->index, mux_chip->controllers);
>> +		put_device(&mux_chip->dev);
>> +		return ERR_PTR(-EINVAL);
>> +	}
>> +
>> +	return &mux_chip->mux[chosen->index];
>>   }
>>   EXPORT_SYMBOL_GPL(mux_control_get);
>>   
>> diff --git a/include/linux/mux/consumer.h b/include/linux/mux/consumer.h
>> index ea96d4c82be7..912dd48a3a5d 100644
>> --- a/include/linux/mux/consumer.h
>> +++ b/include/linux/mux/consumer.h
>> @@ -18,6 +18,17 @@
>>   struct device;
>>   struct mux_control;
>>   
> 
> I want a kernel-doc comment here, describing the structure.

Ok.

>> +struct mux_lookup {
>> +	struct list_head list;
>> +	const char *provider;
>> +	unsigned int index;
>> +	const char *dev_id;
>> +	const char *mux_name;
>> +};
>> +
>> +void mux_add_table(struct mux_lookup *table, size_t num);
>> +void mux_remove_table(struct mux_lookup *table, size_t num);
>> +
> 
> I'm not sure if consumer.h is the right place for this, but it can
> be moved when I think of something better. Which I can't for the
> moment...
> 
>>   unsigned int mux_control_states(struct mux_control *mux);
>>   int __must_check mux_control_select(struct mux_control *mux,
>>   				    unsigned int state);
>>
> 

I will address all comments for v2 of series.

Regards,

Hans