[v2,1/2] doc: bbdev device discovery clarification

  Adding more context and information related the data exposed
through device discovery notably for FEC and FFT operations.

Signed-off-by: Nicolas Chautru <nicolas.chautru@intel.com>
---
 doc/guides/prog_guide/bbdev.rst | 60 ++++++++++++++++++++++++++++-----
 lib/bbdev/rte_bbdev.h           |  6 ++++
 2 files changed, 57 insertions(+), 9 deletions(-)
  

On 10/13/23 23:42, Nicolas Chautru wrote:
> Adding more context and information related the data exposed
> through device discovery notably for FEC and FFT operations.
> 
> Signed-off-by: Nicolas Chautru <nicolas.chautru@intel.com>
> ---
>   doc/guides/prog_guide/bbdev.rst | 60 ++++++++++++++++++++++++++++-----
>   lib/bbdev/rte_bbdev.h           |  6 ++++
>   2 files changed, 57 insertions(+), 9 deletions(-)
> 
> diff --git a/doc/guides/prog_guide/bbdev.rst b/doc/guides/prog_guide/bbdev.rst
> index c43e478eda..01a8a6d79b 100644
> --- a/doc/guides/prog_guide/bbdev.rst
> +++ b/doc/guides/prog_guide/bbdev.rst
> @@ -261,16 +261,58 @@ information:
>     structure, this is where capabilities reside along with other specifics like:
>     maximum queue sizes and priority level.
>   
> -.. code-block:: c
> +.. literalinclude:: ../../../lib/bbdev/rte_bbdev.h
> +   :language: c
> +   :start-after: Structure rte_bbdev_driver_info 8<
> +   :end-before: >8 End of structure rte_bbdev_driver_info.
>   
> -    struct rte_bbdev_info {
> -        int socket_id;
> -        const char *dev_name;
> -        const struct rte_device *device;
> -        uint16_t num_queues;
> -        bool started;
> -        struct rte_bbdev_driver_info drv;
> -    };
> +.. literalinclude:: ../../../lib/bbdev/rte_bbdev.h
> +   :language: c
> +   :start-after: Structure rte_bbdev_info 8<
> +   :end-before: >8 End of structure rte_bbdev_info.
> +
> +Capabilities details for LDPC Decoder
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +On top of the ``RTE_BBDEV_LDPC_<*>`` capabilities the device also exposes the LLR numerical
> +representation expected by the decoder as a fractional fixed-point representation.
> +For instance, when the representation (``llr_size``, ``llr_decimals``) = (8, 2) respectively,
> +this means that each input LLR in the data provided by the application must be computed as 8 total
> +bits (including sign bit) where 2 of these are fractions bits (also referred to as S8.2 format).
> +It is up to the user application during LLR generation to scale the LLR according to this
> +optimal numerical representation. Any mis-scaled LLR would cause wireless performance degradation.
> +
> +The ``harq_buffer_size`` exposes the amount of dedicated DDR made available for the device operation.
> +This is specific for accelerator non-integrated on the CPU (separate PCIe device) which may
> +include separate on-card memory.
> +
> +Capabilities details for FFT function
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +The total number of distinct time windows supported for the post-FFT point-wise multiplication is
> +exposed as ``fft_windows_num``. The ``window_index`` provided for each cyclic shift in each
> +``rte_bbdev_op_fft`` operation is expected to be limited to that size.
> +
> +The information related to the width of each of these pre-configured window is also exposed
> +using the ``fft_window_width`` array. This provides the number of non-null samples used for each
> +window index when scaling back the size to a reference of 1024 FFT. The actual shape size is
> +effectively scaled up or down based on the dynamic size of the FFT operation being used.
> +
> +This allows to distinguish different version of the flexible pointwise windowing applied to the
> +FFT and exposes this platform configuration to the application.
> +
> +Other optional capabilities exposed during device discovery
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +The device status can be used to expose additional information related to the state of the
> +platform notably based on its configuration state or related to error management
> +(correctable or non).
> +
> +The queue topology exposed to the device is provided on top of the capabilities. This provides
> +the number of queues available for the exposed bbdev device (the physical device may have more)
> +for each operation as well as the different level of priority available for arbitration.
> +These are based on the arrays and parameters ``num_queues``, ``queue_priority``,
> +``max_num_queues``, ``queue_size_lim``.
>   
>   
>   Operation Processing
> diff --git a/lib/bbdev/rte_bbdev.h b/lib/bbdev/rte_bbdev.h
> index d12e2e7fbc..925c78cae1 100644
> --- a/lib/bbdev/rte_bbdev.h
> +++ b/lib/bbdev/rte_bbdev.h
> @@ -313,6 +313,8 @@ int
>   rte_bbdev_stats_reset(uint16_t dev_id);
>   
>   /** Device information supplied by the device's driver */
> +
> +/* Structure rte_bbdev_driver_info 8< */
>   struct rte_bbdev_driver_info {
>   	/** Driver name */
>   	const char *driver_name;
> @@ -352,6 +354,7 @@ struct rte_bbdev_driver_info {
>   	/** FFT windowing width for 2048 FFT - size defined in capability. */
>   	uint16_t *fft_window_width;
>   };
> +/* >8 End of structure rte_bbdev_driver_info. */
>   
>   /** Macro used at end of bbdev PMD list */
>   #define RTE_BBDEV_END_OF_CAPABILITIES_LIST() \
> @@ -361,6 +364,8 @@ struct rte_bbdev_driver_info {
>    * Device information structure used by an application to discover a devices
>    * capabilities and current configuration
>    */
> +
> +/* Structure rte_bbdev_info 8< */
>   struct rte_bbdev_info {
>   	int socket_id;  /**< NUMA socket that device is on */
>   	const char *dev_name;  /**< Unique device name */
> @@ -369,6 +374,7 @@ struct rte_bbdev_info {
>   	bool started;  /**< Set if device is currently started */
>   	struct rte_bbdev_driver_info drv;  /**< Info from device driver */
>   };
> +/* >8 End of structure rte_bbdev_info. */
>   
>   /**
>    * Retrieve information about a device.

Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

Thanks,
Maxime