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     altera_avgen — driver for generic Altera Avalon-bus-attached, memory-mapped devices


     device altera_avgen

     In /boot/device.hints:"nexus0"


     The altera_avgen device driver provides generic support for memory-mapped devices on the
     Altera Avalon bus.  device.hints entries configure the address, size, I/O disposition, and
     /dev device node name that will be used.  The open(2), read(2), write(2), and mmap(2) system
     calls (and variations) may be used on altera_avgen device nodes, subject to constraints
     imposed using device.hints entries.  Although reading and writing mapped memory is
     supported, altera_avgen does not currently support directing device interrupts to userspace.

     A number of device.hints sub-fields are available to configure altera_avgen device

     maddr    base physical address of the memory region to export; must be aligned to width

     msize    length of the memory region export; must be aligned to width

     width    Granularity at which read(2) and write(2) operations will be performed.  Larger
              requests will be broken down into width -sized operations; smaller requests will be
              rejected.  I/O operations must be aligned to width.

     fileio   allowed file descriptor operations; r authorizes read(2); w authorizes write(2).

     mmapio   allowed mmap(2) permissions; w authorizes PROT_WRITE; r authorizes PROT_READ; x
              authorizes PROT_EXEC.

     devname  specifies a device name relative to /dev.

     devunit  specifies a device unit number; no unit number is used if this is unspecified.


     mmap(2), open(2), read(2), write(2)


     The altera_avgen device driver first appeared in FreeBSD 10.0.


     The altera_avgen device driver and this manual page were developed by SRI International and
     the University of Cambridge Computer Laboratory under DARPA/AFRL contract (FA8750-10-C-0237)
     (“CTSRD”), as part of the DARPA CRASH research programme.  This device driver was written by
     Robert N. M. Watson.


     altera_avgen is intended to support the writing of userspace device drivers; however, it
     does not permit directing interrupts to userspace, only memory-mapped I/O.

     altera_avgen supports only a nexus bus attachment, which is appropriate for system-on-chip
     busses such as Altera's Avalon bus.  If the target device is off of another bus type, then
     additional bus attachments will be required.