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altera_avgen — driver for generic Altera Avalon-bus-attached, memory-mapped devices
device altera_avgen In /boot/device.hints: hint.altera_avgen.0.at="nexus0" hint.altera_avgen.0.maddr=0x7f00a000 hint.altera_avgen.0.msize=20 hint.altera_avgen.0.width=4 hint.altera_avgen.0.fileio="rw" hint.altera_avgen.0.devname="berirom"
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 instances: 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.
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.