Re: [PATCH] mmc: boot partition ro lock support

[Chris Ball <cjb@laptop.org>]

Hi Linus,

On Sat, Oct 22 2011, Linus Walleij wrote:
> So what about a cmdline approach? That makes it possible
> for people who are willingly recompiling and hacking their kernels
> to tinker with this if they absolutely want to go in on that
> partition, make it rw and change stuff.
>
> ...org have I just got all this backwards...?

Regarding this patch, we're not so worried that someone will take a
read-only boot partition and make it read-write and do something wrong;
sysfs is good enough to protect against that happening (at least by
mistake).

What we're worried about is someone issuing the perm read-only command,
and not realizing that it really means that they can never ever write
any more changes to their eMMC -- it's a one-time fuse -- and perhaps
further not realizing that this may make their expensive cell phone
become a brick of some sort, depending on how much the bootloader or
OS depends on having r/w access.

I don't even know that I'd want to make such an option available via a
boot argument, since boot arguments are often misunderstood.  As Andrei
says, it doesn't sound like something a regular user (as opposed to an
OEM) should ever have reason to do.  I'd rather leave it to specialized
manufacturing equipment.

Does that make sense?  Thanks,

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