Re: [PATCH v4] mmc: core: allow detection of locked cards

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

On 2024-06-20 14:38, Ulf Hansson wrote:
> On Thu, 6 Jun 2024 at 15:12, <linux-mmc@danman.eu> wrote:
>> 
>> From: Daniel Kucera <linux-mmc@danman.eu>
>> 
>> Locked SD card will not reply to SEND_SCR or SD_STATUS commands
>> so it was failing to initialize previously. When skipped,
>> the card will get initialized and CMD42 can be sent using
>> ioctl to unlock the card or remove password protection.
>> For eMMC, this is not necessary because all initialization
>> commands are allowed in locked state.
>> Until unlocked, all read/write calls will timeout.
> 
> Skipping the commands above, only means the card gets partially
> initialized.

Correct, but it's an improvement in comparison to current state.

> Leaving a card in that state seems fragile.

Fragile in what sense? Nothing can happen to the card as it is locked.

> What will
> happen to upper block layers and filesystems when trying to access it?

Everything will simply time-out.

> 
> Several years ago Al Cooper made an attempt [1] to manage the
> unlocking of the card during initialization, by finding the password
> through the "keys" subsystem. The series didn't really make it to the
> upstream kernel, but overall the approach seemed to make sense to me.
> It should allow us to complete the initialization of the card inside
> the kernel and prevent unnecessary complexity for userspace to manage.

Yes, he did a great work but obviously no-one got too excited to 
review/merge
his work. His solution was complex.

Mine targets the smallest change possible to make it work at least.
I wanted to avoid a solution that would be hard to test, review and 
maintain.
Especially when there is only a small interest in the feature.

> Perhaps you can have a closer look at that series and see if it's
> possible to update it?

I don't think I have the skills to revive his work.

> 
> Kind regards
> Uffe

BR
Daniel

> 
> [1]
> https://lore.kernel.org/linux-mmc/1433526147-25941-1-git-send-email-alcooperx@gmail.com/
> 
>> 
>> Signed-off-by: Daniel Kucera <linux-mmc@danman.eu>
>> ---
>>  drivers/mmc/core/sd.c | 13 ++++++++++++-
>>  1 file changed, 12 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
>> index 1c8148cdd..ae821df7d 100644
>> --- a/drivers/mmc/core/sd.c
>> +++ b/drivers/mmc/core/sd.c
>> @@ -928,8 +928,19 @@ int mmc_sd_setup_card(struct mmc_host *host, 
>> struct mmc_card *card,
>>         bool reinit)
>>  {
>>         int err;
>> +       u32 card_status;
>> 
>> -       if (!reinit) {
>> +       err = mmc_send_status(card, &card_status);
>> +       if (err){
>> +               pr_err("%s: unable to get card status\n", 
>> mmc_hostname(host));
>> +               return err;
>> +       }
>> +
>> +       if (card_status & R1_CARD_IS_LOCKED){
>> +               pr_warn("%s: card is locked\n", mmc_hostname(host));
>> +       }
>> +
>> +       if (!reinit && !(card_status & R1_CARD_IS_LOCKED)) {
>>                 /*
>>                  * Fetch SCR from card.
>>                  */
>> --
>> 2.34.1
>>