Re: [PATCH] Add commandline partitions for block devices v2

From: Ulf Hansson
Date: Wed Jun 23 2010 - 04:46:28 EST


Andries E. Brouwer wrote:
On Tue, Jun 22, 2010 Andrew Morton wrote:
On Tue, 8 Jun 2010 Linus Walleij wrote:

From: Ulf Hansson <ulf.hansson@xxxxxxxxxxxxxx>

This adds an option to pass in block device partitions from the kernel
cmdline.

The rationale is that in embedded systems we sometimes have no standard
partition table available: often due to the fact that raw binary data is
read out from the first sectors of the device by ROM code in ASICs. We
have for a long time supplied custom partition information to embedded
flash memories through the MTDparts interface which has similar
semantics, and with the advent of embedded MMC block devices this now
comes to standard block devices.

There exist ioctls BLKPG_ADD_PARTITION and BLKPG_DEL_PARTITION that
allow one to add or remove partitions at run time, without having
a partition table, or without having a partition table in a format
understood by the kernel. Things can be done in user space.

In general there are many things one would like the kernel to do at
init time, and it is a bad idea to do all of this from the kernel
command line. So adding options like these should be done only
if it would be really awkward to do the same from an initial
ramdisk.

Andries

I see your point!

Although, in an embedded system it is not always convenient to use an initial ramdisk. Instead your init program will be found directy from your rootfs, which means the kernel must itself be able to setup the partitions.

Regards
Uffe

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