Erasing MMC partition from kernel module, what's best way to do that?

Erasing MMC partition from kernel module, what's best way to do that?

[JONGMAN HEO]

Hi all,
Please excuse me, I have some noob question regarding MMC.

I'd like to erase(discard) certain MMC partition from kernel space (i.e. kernel module).
I know this is quite ugly design, but I have no choice but to implement the feature (erasing given MMC partition) within kernel space for other reasons.

Assume /dev/mmcblk0p2 needs to be erased.

First, I tried to use BLKDISCARD ioctl. From user space, it works.
In kernel space, I had to use ugly code, like set_fs(), filp_open(), etc in order to access "/dev/mmcblk0p2" device.
I stuck at sys_ioctl(), which is not exported symbol so that I couldn't use the sys_ioctl() from my module for the BLKDISCARD ioctl.

Alternatively, I want to make a new exported API to execute the discard request for "/dev/mmcblk0p2" device (like mmc_test_area_erase() in mmc_test.c).
Here, it seems that I need to get "struct mmc_card *card" instance, which is a first parameter of mmc_erase().

How can I get the "card" instance for current MMC device? Is there any way to do that?

Thanks in advance,
Jongman.

Re: Erasing MMC partition from kernel module, what's best way to do that?

[Chris Ball]

Hi,

On Mon, Jan 09 2012, JONGMAN HEO wrote:
> Hi all,
> Please excuse me, I have some noob question regarding MMC.
>
> I'd like to erase(discard) certain MMC partition from kernel space
> (i.e. kernel module).
> I know this is quite ugly design, but I have no choice but to
> implement the feature (erasing given MMC partition) within kernel
> space for other reasons.
>
> Assume /dev/mmcblk0p2 needs to be erased.
>
> First, I tried to use BLKDISCARD ioctl. From user space, it works.
> In kernel space, I had to use ugly code, like set_fs(), filp_open(),
> etc in order to access "/dev/mmcblk0p2" device.
> I stuck at sys_ioctl(), which is not exported symbol so that I
> couldn't use the sys_ioctl() from my module for the BLKDISCARD ioctl.
>
> Alternatively, I want to make a new exported API to execute the
> discard request for "/dev/mmcblk0p2" device (like
> mmc_test_area_erase() in mmc_test.c).
> Here, it seems that I need to get "struct mmc_card *card" instance,
> which is a first parameter of mmc_erase().
>
> How can I get the "card" instance for current MMC device? Is there any
> way to do that?

I don't think we'll be interested in helping you with this -- as you
say, this is a very ugly design, and we already have the proper
userspace solution.

- Chris.
-- 
Chris Ball   <cjb@laptop.org>   <http://printf.net/>
One Laptop Per Child