Re: [PATCH] mmc-utils: implemented CMD42 locking/unlocking

[Daniel Kucera <linux-mmc@danman.eu>]

On 2024-05-20 11:08, Christian Loehle wrote:
> On 5/19/24 08:08, linux-mmc@danman.eu wrote:
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>> From: Daniel Kucera <linux-mmc@danman.eu>
>> 
>> Implemented locking/unlocking using CMD42 according to Micron
>> Technical Note
>> 
>> original link 
>> https://media-www.micron.com/-/media/client/global/documents/products/technical-note/sd-cards/tnsd01_enable_sd_lock_unlock_in_linux.pdf?rev=03f03a6bc0f8435fafa93a8fc8e88988
>> currently available at 
>> https://github.com/danielkucera/esp32-sdcard/blob/master/tnsd01_enable_sd_lock_unlock_in_linux.pdf
> 
> You explained it nicely in v1 why this feature is indeed more
> dangerous than a simple erase:
> https://lore.kernel.org/linux-mmc/DM6PR04MB6575AC22506EDEBB7C7E9310FCE82@DM6PR04MB6575.namprd04.prod.outlook.com/T/#m4241fce85459336e2ca4d2abbcccf6d6227e9501
> 
> Locking a card will essentially brick it for all practical purposes if
> it is removed (or the system shuts down)
> between locking and unlocking until mmcblk supports initialization of
> locked cards.
> I'd upstream that first, I had a similar patch like you mentioned, but
> didn't get around to it.

I think this is a chicken-egg problem:
If you don't have the tools to lock you cannot test correct detection 
with kernel.
If you don't have kernel supporting locked cards you cannot unlock (but 
can lock).

Regarding the potential damage: what can cause a bigger damage? Loosing 
data or loosing the medium?

But anyway, I will prepare the kernel patch shortly.

D.