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

[Daniel Baluta <daniel.baluta@intel.com>]

On Thu, Apr 16, 2015 at 12:01 PM, Robert Dolca <robert.dolca@intel.com> 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.

s/width/with

>
>  # 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

s/what if/what is

> 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.

This patch is very useful. Also I think that the userspace ABI is good. We need
to work on the in-kernel API because I think we can do better.

We should create a separate function that "attaches" a trigger with
a device.

So, the sequence at probe will be:

indio = iio_device_alloc();
trig = iio_trigger_alloc();

iio_trigger_attach(indio, trig);

iio_trigger_register();
iio_device_register();

The sequence at remove will be in reverse order, where we
would introduce iio_trigger_detach().

We might want document the ABI here:
http://lxr.free-electrons.com/source/Documentation/ABI/testing/sysfs-bus-iio

>
> Signed-off-by: Robert Dolca <robert.dolca@intel.com>
> ---
>  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);
> +       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;
> +       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;

Better name for this would be trigger_list (see buffer_list or chan_attr_list
in the same structure).

Also, please update the doc string above.

>  };
>
>  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;
>  };

The same observation about the doc string.

>
>
> @@ -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
>   *
> --
> 1.9.1
>
> --
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