Documentation/admin-guide/devices.txt

Source file repositories/reference/linux-study-clean/Documentation/admin-guide/devices.txt

File Facts

System
Linux kernel
Corpus path
Documentation/admin-guide/devices.txt
Extension
.txt
Size
106521 bytes
Lines
3083
Domain
Support Tooling And Documentation
Bucket
Documentation
Inferred role
Support Tooling And Documentation: documentation
Status
atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

0		Unnamed devices (e.g. non-device mounts)
		  0 = reserved as null device number
		See block major 144, 145, 146 for expansion areas.

   1 char	Memory devices
		  1 = /dev/mem		Physical memory access
		  2 = /dev/kmem		OBSOLETE - replaced by /proc/kcore
		  3 = /dev/null		Null device
		  4 = /dev/port		I/O port access
		  5 = /dev/zero		Null byte source
		  6 = /dev/core		OBSOLETE - replaced by /proc/kcore
		  7 = /dev/full		Returns ENOSPC on write
		  8 = /dev/random	Nondeterministic random number gen.
		  9 = /dev/urandom	Faster, less secure random number gen.
		 10 = /dev/aio		Asynchronous I/O notification interface
		 11 = /dev/kmsg		Writes to this come out as printk's, reads
					export the buffered printk records.
		 12 = /dev/oldmem	OBSOLETE - replaced by /proc/vmcore

   1 block	RAM disk
		  0 = /dev/ram0		First RAM disk
		  1 = /dev/ram1		Second RAM disk
		    ...
		250 = /dev/initrd	Initial RAM disk

		Older kernels had /dev/ramdisk (1, 1) here.
		/dev/initrd refers to a RAM disk which was preloaded
		by the boot loader; newer kernels use /dev/ram0 for
		the initrd.

   2 char	Pseudo-TTY masters
		  0 = /dev/ptyp0	First PTY master
		  1 = /dev/ptyp1	Second PTY master
		    ...
		255 = /dev/ptyef	256th PTY master

		Pseudo-tty's are named as follows:
		* Masters are "pty", slaves are "tty";
		* the fourth letter is one of pqrstuvwxyzabcde indicating
		  the 1st through 16th series of 16 pseudo-ttys each, and
		* the fifth letter is one of 0123456789abcdef indicating
		  the position within the series.

		These are the old-style (BSD) PTY devices; Unix98
		devices are on major 128 and above and use the PTY
		master multiplex (/dev/ptmx) to acquire a PTY on
		demand.

   2 block	Floppy disks
		  0 = /dev/fd0		Controller 0, drive 0, autodetect
		  1 = /dev/fd1		Controller 0, drive 1, autodetect
		  2 = /dev/fd2		Controller 0, drive 2, autodetect
		  3 = /dev/fd3		Controller 0, drive 3, autodetect
		128 = /dev/fd4		Controller 1, drive 0, autodetect
		129 = /dev/fd5		Controller 1, drive 1, autodetect
		130 = /dev/fd6		Controller 1, drive 2, autodetect
		131 = /dev/fd7		Controller 1, drive 3, autodetect

		To specify format, add to the autodetect device number:
		  0 = /dev/fd?		Autodetect format
		  4 = /dev/fd?d360	5.25"  360K in a 360K  drive(1)
		 20 = /dev/fd?h360	5.25"  360K in a 1200K drive(1)
		 48 = /dev/fd?h410	5.25"  410K in a 1200K drive
		 64 = /dev/fd?h420	5.25"  420K in a 1200K drive
		 24 = /dev/fd?h720	5.25"  720K in a 1200K drive
		 80 = /dev/fd?h880	5.25"  880K in a 1200K drive(1)
		  8 = /dev/fd?h1200	5.25" 1200K in a 1200K drive(1)
		 40 = /dev/fd?h1440	5.25" 1440K in a 1200K drive(1)
		 56 = /dev/fd?h1476	5.25" 1476K in a 1200K drive
		 72 = /dev/fd?h1494	5.25" 1494K in a 1200K drive

Annotation

Implementation Notes