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Diffstat (limited to 'drivers/staging/iio/Documentation/ring.txt')
| -rw-r--r-- | drivers/staging/iio/Documentation/ring.txt | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/drivers/staging/iio/Documentation/ring.txt b/drivers/staging/iio/Documentation/ring.txt new file mode 100644 index 000000000000..d2ca6834c169 --- /dev/null +++ b/drivers/staging/iio/Documentation/ring.txt @@ -0,0 +1,61 @@ +Ring buffer support within IIO + +This document is intended as a general overview of the functionality +a ring buffer may supply and how it is specified within IIO. For more +specific information on a given ring buffer implementation, see the +comments in the source code. Note that the intention is to allow +some drivers to specify ring buffers choice at probe or runtime, but +for now the selection is hard coded within a given driver. + +A given ring buffer implementation typically embedded 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 4 function pointers +(preenable, postenable, predisable, postdisable). +These are used to perform implementation specific steps on either side +of the core changing it's current mode to indicate that the ring 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 ring buffer functionality as possible. Note almost all of these +are optional. + +mark_in_use, unmark_in_use + Basically indicate that not changes should be made to the ring + buffer state that will effect the form of the data being captures + (e.g. scan elements or length) + +store_to + If possible, push data to ring buffer. + +read_last + If possible get the most recent entry 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_lots + The primary ring buffer reading function. Note that it may well not return + as much data as requested. The deadoffset is used to indicate that some + initial data in the data array is not guaranteed to be valid. + +mark_param_changed + Used to indicate that something has changed. Used in conjunction with +request_update + If parameters have changed that require reinitialization or configuration of + the ring buffer this will trigger it. + +get_bpd, set_bpd + Get/set the number of bytes for a given reading (single element, not sample set) + The value of bps (bytes per set) is created from a combination of this and the + enabled scan elements. + +get_length / set_length + Get/set the number of sample sets that may be held by the buffer. + +is_enabled + Query if ring buffer is in use +enable + Start the ring buffer. |