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

[Nicolas Chautru <nicolas.chautru@intel.com>]

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.
-- 
2.34.1