Add the rt linux 4.1.3-rt3 as base

[kvmfornfv.git] / kernel / drivers / staging / iio / Documentation / ring.txt

diff --git a/kernel/drivers/staging/iio/Documentation/ring.txt b/kernel/drivers/staging/iio/Documentation/ring.txt
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+Buffer support within IIO
+
+This document is intended as a general overview of the functionality
+a buffer may supply and how it is specified within IIO.  For more
+specific information on a given buffer implementation, see the
+comments in the source code.  Note that some drivers allow buffer
+implementation to be selected at compile time via Kconfig options.
+
+A given buffer implementation typically embeds a struct
+iio_ring_buffer and it is a pointer to this that is provided to the
+IIO core. Access to the embedding structure is typically done via
+container_of functions.
+
+struct iio_ring_buffer contains a struct iio_ring_setup_ops *setup_ops
+which in turn contains the 4 function pointers
+(preenable, postenable, predisable and postdisable).
+These are used to perform device specific steps on either side
+of the core changing its current mode to indicate that the buffer
+is enabled or disabled (along with enabling triggering etc. as appropriate).
+
+Also in struct iio_ring_buffer is a struct iio_ring_access_funcs.
+The function pointers within here are used to allow the core to handle
+as much buffer functionality as possible. Note almost all of these
+are optional.
+
+store_to
+  If possible, push data to the buffer.
+
+read_last
+  If possible, get the most recent scan from the buffer (without removal).
+  This provides polling like functionality whilst the ring buffering is in
+  use without a separate read from the device.
+
+rip_first_n
+  The primary buffer reading function. Note that it may well not return
+  as much data as requested.
+
+request_update
+  If parameters have changed that require reinitialization or configuration of
+  the buffer this will trigger it.
+
+set_bytes_per_datum
+  Set the number of bytes for a complete scan. (All samples + timestamp)
+
+set_length
+  Set the number of complete scans that may be held by the buffer.
+