Re: [PATCH RFC 1/3] iio: Add symlink to triggers in the device's trigger folder

[Jonathan Cameron]

On 16/04/15 05:01, Robert Dolca wrote:
> This patch adds a new function called iio_trigger_register_with_dev
> which is a wrapper for iio_trigger_register. Besides the iio_trigger
> struct this function requires iio_dev struct. It adds the trigger in
> the device's trigger list and saves a reference to the device in the
> trigger's struct.
> 
> When the device is registered, in the trigger folder of the device
> (where current_trigger file resides) a symlink is being created for
> each trigger that was registered width iio_trigger_register_with_dev.
> 
>  # ls -l /sys/bus/iio/devices/iio:device0/trigger/
> total 0
> -rw-r--r--    1 root     root          4096 Apr 16 08:33 current_trigger
> lrwxrwxrwx    1 root     root             0 Apr 16 08:33 trigger0 -> ../../trigg
> er0
> 
> This should be used for device specific triggers. Doing this the user space
> applications can figure out what if the trigger registered by a specific device
> and what should they write in the current_trigger file. Currently some
> applications rely on the trigger name and this does not always work.
> 
> This implementation assumes that the trigger is registered before the device is
> registered. If the order is not this the symlink will not be created but
> everything else will work as before.
> 
> Signed-off-by: Robert Dolca <robert.dolca@xxxxxxxxx>
I was rather hoping we'd get a few more comments on this.
In principle I like the idea, but it's new ABI and does make life
a tiny bit more complex, so what do people think?

Few trivial code comments inline.

> ---
>  drivers/iio/industrialio-core.c    | 20 ++++++++++++
>  drivers/iio/industrialio-trigger.c | 64 ++++++++++++++++++++++++++++++++++++++
>  include/linux/iio/iio.h            |  1 +
>  include/linux/iio/trigger.h        | 24 ++++++++++++++
>  4 files changed, 109 insertions(+)
> 
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index 69feb91..94bcd54 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -26,6 +26,7 @@
>  #include <linux/anon_inodes.h>
>  #include <linux/debugfs.h>
>  #include <linux/iio/iio.h>
> +#include <linux/iio/trigger.h>
>  #include "iio_core.h"
>  #include "iio_core_trigger.h"
>  #include <linux/iio/sysfs.h>
> @@ -988,6 +989,7 @@ struct iio_dev *iio_device_alloc(int sizeof_priv)
>  		}
>  		dev_set_name(&dev->dev, "iio:device%d", dev->id);
>  		INIT_LIST_HEAD(&dev->buffer_list);
> +		INIT_LIST_HEAD(&dev->triggers);
>  	}
>  
>  	return dev;
> @@ -1166,6 +1168,8 @@ static const struct iio_buffer_setup_ops noop_ring_setup_ops;
>  int iio_device_register(struct iio_dev *indio_dev)
>  {
>  	int ret;
> +	struct iio_trigger *trig_info;
> +	struct list_head *pos;
>  
>  	/* If the calling driver did not initialize of_node, do it here */
>  	if (!indio_dev->dev.of_node && indio_dev->dev.parent)
> @@ -1222,6 +1226,13 @@ int iio_device_register(struct iio_dev *indio_dev)
>  	if (ret < 0)
>  		goto error_cdev_del;
>  
> +	list_for_each(pos, &indio_dev->triggers) {
> +		trig_info = list_entry(pos, struct iio_trigger, indio_dev_list);
> +		ret = iio_trigger_link(trig_info);
> +		if (ret < 0)
> +			goto error_cdev_del;
> +	}
> +
>  	return 0;
>  error_cdev_del:
>  	cdev_del(&indio_dev->chrdev);
> @@ -1243,8 +1254,17 @@ EXPORT_SYMBOL(iio_device_register);
>   **/
>  void iio_device_unregister(struct iio_dev *indio_dev)
>  {
> +	struct list_head *pos, *safe;
> +	struct iio_trigger *trig_info;
> +
>  	mutex_lock(&indio_dev->info_exist_lock);
>  
> +	list_for_each_safe(pos, safe, &indio_dev->triggers) {
> +		trig_info = list_entry(pos, struct iio_trigger, indio_dev_list);
> +		list_del(pos);
> +		iio_trigger_unlink(trig_info);
> +	}
> +
>  	device_del(&indio_dev->dev);
>  
>  	if (indio_dev->chrdev.dev)
> diff --git a/drivers/iio/industrialio-trigger.c b/drivers/iio/industrialio-trigger.c
> index d31098e..cebdd10 100644
> --- a/drivers/iio/industrialio-trigger.c
> +++ b/drivers/iio/industrialio-trigger.c
> @@ -57,6 +57,24 @@ static struct attribute *iio_trig_dev_attrs[] = {
>  };
>  ATTRIBUTE_GROUPS(iio_trig_dev);
>  
> +int iio_trigger_register_with_dev(struct iio_dev *indio_dev,
> +				  struct iio_trigger *trig_info)
> +{
> +	int ret;
> +
> +	ret = iio_trigger_register(trig_info);
> +	if (ret < 0)
> +		goto error;
> +
> +	trig_info->indio_dev = indio_dev;
> +	list_add(&trig_info->indio_dev_list, &indio_dev->triggers);
> +
> +	return 0;
> +error:
> +	return ret;
> +}
> +EXPORT_SYMBOL(iio_trigger_register_with_dev);
> +
>  int iio_trigger_register(struct iio_trigger *trig_info)
>  {
>  	int ret;
> @@ -88,6 +106,11 @@ EXPORT_SYMBOL(iio_trigger_register);
>  
>  void iio_trigger_unregister(struct iio_trigger *trig_info)
>  {
> +	if (trig_info->indio_dev) {
> +		iio_trigger_unlink(trig_info);
> +		list_del(&trig_info->indio_dev_list);
> +	}
> +
>  	mutex_lock(&iio_trigger_list_lock);
>  	list_del(&trig_info->list);
>  	mutex_unlock(&iio_trigger_list_lock);
> @@ -98,6 +121,47 @@ void iio_trigger_unregister(struct iio_trigger *trig_info)
>  }
>  EXPORT_SYMBOL(iio_trigger_unregister);
>  
> +int iio_trigger_link(struct iio_trigger *trig_info)
> +{
> +	int ret;
> +	char *name;
> +	struct iio_dev *indio_dev;
> +
> +	indio_dev = trig_info->indio_dev;
> +	if (!indio_dev)
> +		return -EINVAL;
> +
> +	name = kasprintf(GFP_KERNEL, "trigger%d", trig_info->id);
> +	if (!name)
> +		return -ENOMEM;
> +
> +	ret = sysfs_add_link_to_group(&indio_dev->dev.kobj, "trigger",
> +				      &trig_info->dev.kobj, name);
> +	kfree(name);
blank line here.
> +	return ret;
> +}
> +EXPORT_SYMBOL(iio_trigger_link);
> +
> +int iio_trigger_unlink(struct iio_trigger *trig_info)
> +{
> +	char *name;
> +	struct iio_dev *indio_dev;
> +
> +	indio_dev = trig_info->indio_dev;
> +	if (!trig_info->indio_dev)
> +		return -EINVAL;
> +
> +	name = kasprintf(GFP_KERNEL, "trigger%d", trig_info->id);
> +	if (!name)
> +		return -ENOMEM;
> +
> +	sysfs_remove_link_from_group(&indio_dev->dev.kobj, "trigger", name);
> +	kfree(name);
> +	trig_info->indio_dev = NULL;
and another blank line here.
> +	return 0;
> +}
> +EXPORT_SYMBOL(iio_trigger_unlink);
> +
>  static struct iio_trigger *iio_trigger_find_by_name(const char *name,
>  						    size_t len)
>  {
> diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
> index 878d861..9ff54ef 100644
> --- a/include/linux/iio/iio.h
> +++ b/include/linux/iio/iio.h
> @@ -495,6 +495,7 @@ struct iio_dev {
>  	struct dentry			*debugfs_dentry;
>  	unsigned			cached_reg_addr;
>  #endif
> +	struct list_head		triggers;
>  };
>  
>  const struct iio_chan_spec
> diff --git a/include/linux/iio/trigger.h b/include/linux/iio/trigger.h
> index fa76c79..4001e44 100644
> --- a/include/linux/iio/trigger.h
> +++ b/include/linux/iio/trigger.h
> @@ -70,6 +70,9 @@ struct iio_trigger {
>  	struct iio_subirq subirqs[CONFIG_IIO_CONSUMERS_PER_TRIGGER];
>  	unsigned long pool[BITS_TO_LONGS(CONFIG_IIO_CONSUMERS_PER_TRIGGER)];
>  	struct mutex			pool_lock;
> +
> +	struct iio_dev			*indio_dev;
> +	struct list_head		indio_dev_list;
>  };
>  
>  
> @@ -117,6 +120,15 @@ static inline void *iio_trigger_get_drvdata(struct iio_trigger *trig)
>  }
>  
>  /**
> + * iio_trigger_register_width_dev() - register a trigger with the IIO core
> + * and associate it with a device
> + * @iio_dev: device to associate the trigger with
> + * @trig_info:	trigger to be registered
> + **/
> +int iio_trigger_register_with_dev(struct iio_dev *indio_dev,
> +				  struct iio_trigger *trig_info);
> +
> +/**
>   * iio_trigger_register() - register a trigger with the IIO core
>   * @trig_info:	trigger to be registered
>   **/
> @@ -129,6 +141,18 @@ int iio_trigger_register(struct iio_trigger *trig_info);
>  void iio_trigger_unregister(struct iio_trigger *trig_info);
>  
>  /**
> + * Add a symlink to the trigger in the devices' trigger folder
> + * @trig_info:  symlink destination trigger
> + */
> +int iio_trigger_link(struct iio_trigger *trig_info);
> +
> +/**
> + * Remove the trigger's symlink from the device's trigger folder
> + * @trig_info: symlink destination trigger
> + */
> +int iio_trigger_unlink(struct iio_trigger *trig_info);
> +
> +/**
>   * iio_trigger_poll() - called on a trigger occurring
>   * @trig:	trigger which occurred
>   *
> 

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