[PATCH] Add documentation for snd_ctl_elem_list_*

[Takashi Iwai]

On Sun, 16 Aug 2020 12:49:45 +0200,
Tanjeff Moos wrote:
> 
> On 16/08/2020 09:39, Takashi Iwai wrote:
> > The contents look good to me, but could you give your Signed-off-by
> > line for merging the patch?
> > 
> 
> Here we go:

Your embedded patch isn't cleanly applicable due to the line breaks
your MUA has put at reply.  Please fix your MUA setup, or submit via
git-send-email again.



thanks,

Takashi

> >From 731895b67fcae743551989a5dd04382003e66560 Mon Sep 17 00:00:00 2001
> From: "Tanjeff-N. Moos" <tanjeff at cccmz.de>
> Date: Fri, 14 Aug 2020 08:40:28 +0200
> Subject: [PATCH] Add documentation for snd_ctl_elem_list_*.
> 
> Signed-off-by: Tanjeff-N. Moos <tanjeff at cccmz.de>
> ---
>  include/control.h     | 81 +++++++++++++++++++++++++++++++++++++++++--
>  src/control/control.c | 80 ++++++++++++++++++++++++++++++++++++------
>  2 files changed, 148 insertions(+), 13 deletions(-)
> 
> diff --git a/include/control.h b/include/control.h
> index 02db72d4..9deec6f3 100644
> --- a/include/control.h
> +++ b/include/control.h
> @@ -56,7 +56,75 @@ typedef struct _snd_ctl_card_info snd_ctl_card_info_t;
>  /** CTL element identifier container */
>  typedef struct _snd_ctl_elem_id snd_ctl_elem_id_t;
> 
> -/** CTL element identifier list container */
> +/** CTL element list container
> + *
> + * This is a list of CTL elements. The list contains management
> + * information (e.g. how many elements the sound card has) as well as
> + * the element identifiers. All functions which operate on the list
> + * are named snd_ctl_elem_list_*().
> + *
> + * \par Memory management
> + *
> + * There are two memory areas to deal with: The list container itself
> + * and the memory for the element identifiers.
> + *
> + * To manage the area for the list container, the following functions
> + * are used:
> + *
> + * - snd_ctl_elem_list_malloc() / snd_ctl_elem_list_free() to allocate
> + *   and free memory on the heap, or
> + * - snd_ctl_elem_list_alloca() to allocate the memory on the
> + *   stack. This memory is auto-released when the stack is unwound.
> + *
> + * To manage the space for the element identifiers, the
> + * snd_ctl_elem_list_alloc_space() and snd_ctl_elem_list_free_space()
> + * are used. Allocating the right amount of space can be achieved by
> + * first obtaining the number of elements and then calling
> + * snd_ctl_elem_list_alloc_space():
> + *
> + * \code
> + *   snd_ctl_elem_list_t* list;
> + *   int count;
> + *
> + *   // Initialise list
> + *   snd_ctl_elem_list_malloc(&list);
> + *
> + *   // Get number of elements
> + *   snd_ctl_elem_list(ctl, list);
> + *   count = snd_ctl_elem_list_get_count(list);
> + *
> + *   // Allocate space for identifiers
> + *   snd_ctl_elem_list_alloc_space(list, count);
> + *
> + *   // Get identifiers
> + *   snd_ctl_elem_list(ctl, list); // yes, this is same as above :)
> + *
> + *   // Do something useful with the list...
> + *
> + *   // Cleanup
> + *   snd_ctl_elem_list_free_space(list);
> + *   snd_ctl_elem_list_free(list);
> + * \endcode
> + *
> + *
> + * \par The Elements
> + *
> + * The elements in the list are accessed using an index. This index is
> + * the location in the list; Don't confuse it with the 'index' of the
> + * element identifier. For example:
> + *
> + * \code
> + *     snd_ctl_elem_list_t list;
> + *     unsigned int element_index;
> + *
> + *     // Allocate space, fill list ...
> + *
> + *     element_index = snd_ctl_elem_list_get_index(&list, 2);
> + * \endcode
> + *
> + * This will access the 3rd element in the list (index=2) and get the
> + * elements index from the driver (which might be 13, for example).
> + */
>  typedef struct _snd_ctl_elem_list snd_ctl_elem_list_t;
> 
>  /** CTL element info container */
> @@ -354,11 +422,18 @@ void snd_ctl_event_copy(snd_ctl_event_t *dst,
> const snd_ctl_event_t *src);
>  snd_ctl_event_type_t snd_ctl_event_get_type(const snd_ctl_event_t *obj);
> 
>  size_t snd_ctl_elem_list_sizeof(void);
> +
>  /** \hideinitializer
> - * \brief allocate an invalid #snd_ctl_elem_list_t using standard alloca
> - * \param ptr returned pointer
> + *
> + * \brief Allocate a #snd_ctl_elem_list_t using standard alloca.
> + *
> + * The memory is allocated on the stack and will automatically be
> + * released when the stack unwinds (i.e. no free() is needed).
> + *
> + * \param ptr Pointer to allocated memory.
>   */
>  #define snd_ctl_elem_list_alloca(ptr) __snd_alloca(ptr, snd_ctl_elem_list)
> +
>  int snd_ctl_elem_list_malloc(snd_ctl_elem_list_t **ptr);
>  void snd_ctl_elem_list_free(snd_ctl_elem_list_t *obj);
>  void snd_ctl_elem_list_clear(snd_ctl_elem_list_t *obj);
> diff --git a/src/control/control.c b/src/control/control.c
> index e21e8f1d..1bcf1ab2 100644
> --- a/src/control/control.c
> +++ b/src/control/control.c
> @@ -280,6 +280,21 @@ int snd_ctl_card_info(snd_ctl_t *ctl,
> snd_ctl_card_info_t *info)
> 
>  /**
>   * \brief Get a list of element identifiers
> + *
> + * Before calling this function, memoru must be allocated using
> + * snd_ctl_elem_list_malloc().
> + *
> + * This function obtains data from the sound card driver and puts it
> + * into the list.
> + *
> + * If there was space allocated for the element identifiers (using
> + * snd_ctl_elem_list_alloc_space()), information will be filled in. If
> + * too little space was allocated, only a part of the elements will be
> + * queried. If there was too much space allocated, some of it remains
> + * unused. Use snd_ctl_elem_list_get_count() and
> + * snd_ctl_elem_list_get_used() to obtain information about space
> + * usage. See #snd_ctl_elem_list_t to learn more.
> + *
>   * \param ctl CTL handle
>   * \param list CTL element identifiers list pointer
>   * \return 0 on success otherwise a negative error code
> @@ -1508,9 +1523,14 @@ const char
> *snd_ctl_event_type_name(snd_ctl_event_type_t type)
> 
>  /**
>   * \brief allocate space for CTL element identifiers list
> - * \param obj CTL element identifiers list
> - * \param entries Entries to allocate
> - * \return 0 on success otherwise a negative error code
> + *
> + * The space can be released with snd_ctl_elem_list_free_space().
> + *
> + * \param obj CTL element identifiers list.
> + * \param entries How many entries to allocate. See
> + *        #snd_ctl_elem_list_t to learn how to obtain
> + *        this number in advance.
> + * \return 0 on success otherwise a negative error code.
>   */
>  int snd_ctl_elem_list_alloc_space(snd_ctl_elem_list_t *obj, unsigned
> int entries)
>  {
> @@ -1526,6 +1546,10 @@ int
> snd_ctl_elem_list_alloc_space(snd_ctl_elem_list_t *obj, unsigned int entries
> 
>  /**
>   * \brief free previously allocated space for CTL element identifiers list
> + *
> + * Releases space previously allocated using
> + * snd_ctl_elem_list_alloc_space().
> + *
>   * \param obj CTL element identifiers list
>   */
>  void snd_ctl_elem_list_free_space(snd_ctl_elem_list_t *obj)
> @@ -2016,7 +2040,7 @@ snd_ctl_event_type_t snd_ctl_event_get_type(const
> snd_ctl_event_t *obj)
>  }
> 
>  /**
> - * \brief get size of #snd_ctl_elem_list_t
> + * \brief get size of #snd_ctl_elem_list_t.
>   * \return size in bytes
>   */
>  size_t snd_ctl_elem_list_sizeof()
> @@ -2025,7 +2049,10 @@ size_t snd_ctl_elem_list_sizeof()
>  }
> 
>  /**
> - * \brief allocate an invalid #snd_ctl_elem_list_t using standard malloc
> + * \brief allocate a #snd_ctl_elem_list_t using standard malloc.
> + *
> + * The memory can be released using snd_ctl_elem_list_free().
> + *
>   * \param ptr returned pointer
>   * \return 0 on success otherwise negative error code
>   */
> @@ -2039,7 +2066,15 @@ int snd_ctl_elem_list_malloc(snd_ctl_elem_list_t
> **ptr)
>  }
> 
>  /**
> - * \brief frees a previously allocated #snd_ctl_elem_list_t
> + * \brief frees a previously allocated #snd_ctl_elem_list_t.
> + *
> + * Release memory previously allocated using
> + * snd_ctl_elem_list_malloc().
> + *
> + * If you used snd_ctl_elem_list_alloc_space() on the list, you must
> + * use snd_ctl_elem_list_free_space() \em before calling this
> + * function.
> + *
>   * \param obj pointer to object to free
>   */
>  void snd_ctl_elem_list_free(snd_ctl_elem_list_t *obj)
> @@ -2048,7 +2083,15 @@ void snd_ctl_elem_list_free(snd_ctl_elem_list_t *obj)
>  }
> 
>  /**
> - * \brief clear given #snd_ctl_elem_list_t object
> + * \brief Clear given #snd_ctl_elem_list_t object.
> + *
> + * This will make the stored identifiers inaccessible without freeing
> + * their space.
> + *
> + * \warning The element identifier space cannot be freed after calling
> + *          this function. Therefore, snd_ctl_elem_list_free_space()
> + *          must be called in advance.
> + *
>   * \param obj pointer to object to clear
>   */
>  void snd_ctl_elem_list_clear(snd_ctl_elem_list_t *obj)
> @@ -2057,7 +2100,11 @@ void snd_ctl_elem_list_clear(snd_ctl_elem_list_t
> *obj)
>  }
> 
>  /**
> - * \brief copy one #snd_ctl_elem_list_t to another
> + * \brief copy one #snd_ctl_elem_list_t to another.
> + *
> + * This performs a shallow copy. That means the both lists will share
> + * the same space for the elements.  The elements will not be copied.
> + *
>   * \param dst pointer to destination
>   * \param src pointer to source
>   */
> @@ -2080,6 +2127,12 @@ void
> snd_ctl_elem_list_set_offset(snd_ctl_elem_list_t *obj, unsigned int val)
> 
>  /**
>   * \brief Get number of used entries in CTL element identifiers list
> + *
> + * This function returns how many entries are actually filled with
> + * useful information.
> + *
> + * See also snd_ctl_elem_list_get_count().
> + *
>   * \param obj CTL element identifier list
>   * \return number of used entries
>   */
> @@ -2090,7 +2143,14 @@ unsigned int snd_ctl_elem_list_get_used(const
> snd_ctl_elem_list_t *obj)
>  }
> 
>  /**
> - * \brief Get total count of elements present in CTL device
> (information present in every filled CTL element identifiers list)
> + * \brief Get total count of elements present in CTL device
> + *
> + * This function returns how many entries were allocated using
> + * snd_ctl_elem_list_alloc_space(). This information is present after
> + * snd_ctl_elem_list() was called.
> + *
> + * See also snd_ctl_elem_list_get_used().
> + *
>   * \param obj CTL element identifier list
>   * \return total number of elements
>   */
> @@ -2140,7 +2200,7 @@ snd_ctl_elem_iface_t
> snd_ctl_elem_list_get_interface(const snd_ctl_elem_list_t *
>  }
> 
>  /**
> - * \brief Get device part of CTL element identifier for an entry of a
> CTL element identifiers list
> + * \brief Get the device part of CTL element identifier for an entry of
> a CTL element identifiers list
>   * \param obj CTL element identifier list
>   * \param idx Index of entry
>   * \return CTL element related device
> -- 
> 2.17.1
>