ref: d5fae5426816fee74b9323402ce3d67b9eedee06
dir: /sys/man/3/arch/
.TH ARCH 3 .SH NAME arch \- architecture-specific information and control .SH SYNOPSIS .nf .B bind -a #P /dev .sp 0.3v .B /dev/acpitbls .B /dev/archctl .B /dev/cputype .B /dev/ec .B /dev/ioalloc .B /dev/iob .B /dev/iol .B /dev/iow .B /dev/irqalloc .B /dev/msr .B /dev/realmodemem .SH DESCRIPTION This device presents textual information about PC hardware and allows user-level control of the I/O ports on x86-class machines. .PP Reads from .I cputype recover the processor type and clock rate in MHz. Reads from .I archctl yield at least data of this form: .IP .EX cpu AMD64 2201 pge pge on coherence mfence cmpswap cmpswap486 i8253set on cache default uc cache 0x0 1073741824 wb cache 0x3ff00000 1048576 uc .EE .LP Where .L AMD64 is the processor type, .L 2201 is the processor speed in MHz, and .L pge is present only if the `page global extension' capability is present; the next line reflects its setting. .L coherence is followed by one of .LR mb386 , .LR mb586 , .L mfence or .LR nop , showing the form of memory barrier used by the kernel. .L cmpswap is followed by .L cmpswap386 or .LR cmpswap486 , reflecting the form of `compare and swap' used by the kernel. .L i8253set is a flag, indicating the need to explicitly set the Intel 8253 or equivalent timer. There may be lines starting with .L cache that reflect the state of memory caching via MTRRs (memory-type region registers). The second word on the line is .L default or a C-style number which is the base physical address of the region; the third is a C-style length of the region; and the fourth is one of .LR uc (for uncachable), .LR wb (write-back), .LR wc (write-combining), .LR wp (write-protected), or .LR wt (write-through). A region may be a subset of another region, and the smaller region takes precedence. This may be used to make I/O registers uncachable in the midst of a write-combining region mostly used for a video framebuffer, for example. Control messages may be written to .I archctl and use the same syntax as the data read from .IR archctl . Known commands include .LR cache , .LR coherence , .LR i8253set , and .LR pge . . .PP Reads from .I ioalloc return I/O ranges used by each device, one line per range. Each line contains three fields separated by white space: first address in hexadecimal, last address, name of device. .PP Reads from .I irqalloc return the enabled interrupts, one line per interrupt. Each line contains three fields separated by white space: the trap number, the IRQ it is assigned to, and the name of the device using it. .PP Reads and writes to .IR iob , .IR iow , and .IR iol cause 8-bit wide, 16-bit wide, and 32-bit wide requests to I/O ports. The port accessed is determined by the byte offset of the file descriptor. .PP Reads and writes to .I msr go to the P4/P6/Core/Core2/AMD64 MSRs. .PP The .I realmodemem file provides access to the first megabyte of memory. This allows reading BIOS data structures and option ROMs. Writing is limited to the VGA framebuffer at [0xA0000-0xBFFFF]. .PP Reads and writes to .I ec transfer bytes from and to the embedded controller. .PP Reads from .I acpitbls return a concatenation of system ACPI tables. Each table is prefixed with a fixed size header that gives the name sigature and size of the table (see section .IR "5.2.6 System Description Table Header" in the ACPI specification). .SH EXAMPLE The following code reads from an x86 byte I/O port. .IP .EX uchar inportb(unsigned port) { uchar data; if(iobfd == -1) iobfd = open("#P/iob", ORDWR); seek(iobfd, port, 0); if(read(iobfd, &data, sizeof(data)) != sizeof(data)) sysfatal("inportb(0x%4.4ux): %r", port); return data; } .EE .SH SOURCE .B /sys/src/9/pc/devarch.c