microSD card detected with wrong size/capacity

[C M Reinehr]

On Sunday, July 05, 2015 05:44:15 PM Lonni J Friedman via Linux-users wrote:
> I've got a weird one here.  A microSD card which came with a junky old
> Android phone claims to be 4GB on its label, however there's some
> weird marketing nonsense about how "3GB reserved for music".  When I
> plug the card into a reader attached to a linux box, its always
> detected as a 1GB card:
> [3181684.541224] scsi 10:0:0:0: Direct-Access     Generic  STORAGE
> DEVICE   0207 PQ: 0 ANSI: 0
> [3181684.541593] sd 10:0:0:0: Attached scsi generic sg7 type 0
> [3181685.004787] sd 10:0:0:0: [sdg] 1934848 512-byte logical blocks:
> (990 MB/944 MiB)
> 
> 
> I'm guessing that there's something weird going on with the card that
> hides 3GB from the OS somehow.  Has anyone run into this before?  Any
> tips on how to unhide the missing 3GB?
> 
> thanks

I believe that this Wikipedia article may provide a clue:

https://en.wikipedia.org/wiki/Secure_Digital#Storage_capacity_and_incompatibilities

Per the article, a host o/s determines the capacity of an SD card by 
interogating the card for it's Card-Specific Data identification string. The 
article goes into some detail about the format of this string and different 
versions, but the important part is that the o/s knows the size of the card 
based upon the card provided CSD. In this case, I believe that the card 
intentionally is misreporting the size of the card.

HTH.

CMR
-- 
“Three millions of people, armed in the holy cause of liberty, and in such a 
country as that which we possess, are invincible by any force which our enemy 
can send against us. Beside, sir, we shall not fight our battles alone. There 
is a just God who presides over the destinies of Nations, and who will raise 
up friends to fight our battles for us. The battle, sir, is not to the strong 
alone; it is to the vigilant, the active, the brave.” -- Patrick Henry
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