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10 - Introduction
11 -- Background
12 -- Xillybus Overview
14 - Usage
15 -- User interface
16 -- Synchronization
17 -- Seekable pipes
19 - Internals
20 -- Source code organization
21 -- Pipe attributes
22 -- Host never reads from the FPGA
23 -- Channels, pipes, and the message channel
24 -- Data streaming
25 -- Data granularity
26 -- Probing
27 -- Buffer allocation
28 -- The "nonempty" message (supporting poll)
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44 special functionality is needed, and the production volume is relatively low
47 The challenge with FPGAs is that everything is implemented at a very low
50 again, pre-designed building blocks, IP cores, are often used. These are the
59 low-level bus protocol and the somewhat higher-level interface with the host
61 function is a well-known one (e.g. a video adapter card, or a NIC), it can
63 A special driver is then written to present the FPGA as a well-known interface
67 It's however common that the desired data communication doesn't fit any well-
73 interface logic for the FPGA, and write a simple ad-hoc driver for the kernel.
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79 elementary data transport between an FPGA and the host, providing pipe-like
80 data streams with a straightforward user interface. It's intended as a low-
81 effort solution for mixed FPGA-host projects, for which it makes sense to
82 have the project-specific part of the driver running in a user-space program.
91 communication to the user. At the host side, a character device file is used
92 just like any pipe file. On the FPGA side, hardware FIFOs are used to stream
93 the data. This is contrary to a common method of communicating through fixed-
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125 possibly pressing CTRL-C as some stage, even though the xillybus_* pipes have
130 * Supporting non-blocking I/O (by setting O_NONBLOCK on open() ).
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175 FPGA side to the seekable stream. Reading or writing to a certain address in
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194 which execute the DMA-related operations on the bus.
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204 * is_writebuf: The pipe's direction. A non-zero value means it's an FPGA to
212 * allowpartial: A non-zero value means that a read() or write() (whichever
214 choice is a non-zero value, to match standard UNIX behavior.
216 * synchronous: A non-zero value means that the pipe is synchronous. See
223 * exclusive_open: A non-zero value forces exclusive opening of the associated
227 * seekable: A non-zero value indicates that the pipe is seekable. See
230 * supports_nonempty: A non-zero value (which is typical) indicates that the
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253 This mechanism is used on non-PCIe buses as well for the sake of uniformity.
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261 and pipes is necessary only because of channel 0, which is used for interrupt-
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267 Even though a non-segmented data stream is presented to the user at both
279 This is not good enough for creating a TCP/IP-like stream: If the data flow
291 filled buffers being sent) and a latency held fairly low for tails of data.
300 and yet enjoy a stream-like interface.
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373 FPGA side has sent data, but a select() call would still block, because the