Subject: Re: [PATCH 02/11] mux: core: Add support for getting a mux controller
 on a non DT platform
To: Hans de Goede <hdegoede@redhat.com>,
        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>
From: Peter Rosin <peda@axentia.se>
Organization: Axentia Technologies AB
Message-ID: <0c882d23-d008-3d61-27be-3fa22bf59521@axentia.se>
Date: Mon, 4 Sep 2017 13:19:14 +0200
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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?)

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

controllers?

> + */
> +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);

> +
> +	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.

> +
> +	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):

		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.

> +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);
> 

Cheers,
Peter