CONFIG_NVRAM: /dev/nvram support

General informations

The Linux kernel configuration item CONFIG_NVRAM has multiple definitions:

/dev/nvram support found in drivers/char/Kconfig

The configuration item CONFIG_NVRAM:

• prompt: /dev/nvram support
• type: tristate
• depends on: CONFIG_X86 || CONFIG_HAVE_ARCH_NVRAM_OPS
• defined in drivers/char/Kconfig
• found in Linux kernels: 2.5.45–2.5.75, 2.6.0–2.6.39, 3.0–3.19, 4.0–4.20, 5.0–5.19, 6.0–6.8, 6.9-rc+HEAD
• modules built: chrp_nvram, nvram, pmac_nvram

Help text

If you say Y here and create a character special file /dev/nvram with major number 10 and minor number 144 using mknod ("man mknod"), you get read and write access to the non-volatile memory.

/dev/nvram may be used to view settings in NVRAM or to change them (with some utility). It could also be used to frequently save a few bits of very important data that may not be lost over power-off and for which writing to disk is too insecure. Note however that most NVRAM space in a PC belongs to the BIOS and you should NEVER idly tamper with it. See Ralf Brown's interrupt list for a guide to the use of CMOS bytes by your BIOS.

This memory is conventionally called "NVRAM" on PowerPC machines, "CMOS RAM" on PCs, "NVRAM" on Ataris and "PRAM" on Macintoshes.

To compile this driver as a module, choose M here: the module will be called nvram.

found in arch/m68k/Kconfig

The configuration item CONFIG_NVRAM:

• prompt:
• type: bool
• depends on: CONFIG_ATARI
• defined in arch/m68k/Kconfig
• found in Linux kernels: 2.5.45–2.5.75, 2.6.0–2.6.3
• modules built: chrp_nvram, nvram, pmac_nvram

Help text

If you say Y here and create a character special file /dev/nvram with major number 10 and minor number 144 using mknod ("man mknod"), you get read and write access to the 50 bytes of non-volatile memory in the real time clock (RTC), which is contained in every PC and most Ataris.

This memory is conventionally called "CMOS RAM" on PCs and "NVRAM" on Ataris. /dev/nvram may be used to view settings there, or to change them (with some utility). It could also be used to frequently save a few bits of very important data that may not be lost over power-off and for which writing to disk is too insecure. Note however that most NVRAM space in a PC belongs to the BIOS and you should NEVER idly tamper with it. See Ralf Brown's interrupt list for a guide to the use of CMOS bytes by your BIOS.

On Atari machines, /dev/nvram is always configured and does not need to be selected.

To compile this driver as a module, choose M here: the module will be called nvram.

Hardware

LKDDb

Raw data from LKDDb:

• lkddb module chrp_nvram CONFIG_NVRAM : drivers/char/Kconfig : "/dev/nvram support" # in 2.6.16
• lkddb module nvram CONFIG_NVRAM : drivers/char/Kconfig : "/dev/nvram support" # in 2.6.17–2.6.39, 3.0–3.19, 4.0–4.20, 5.0–5.19, 6.0–6.8, 6.9-rc+HEAD
• lkddb module pmac_nvram CONFIG_NVRAM : drivers/char/Kconfig : "/dev/nvram support" # in 2.5.45–2.5.75, 2.6.0–2.6.15

Sources

This page is automaticly generated with free (libre, open) software lkddb(see lkddb-sources).

The data is retrived from:

• Linux kernel
• Linux Kernel Driver DataBase (LKDDb)

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