I was wondering, is it possible to have my Raspberry Pi mount the SD that is also mounted by an digital camera?
I have a scenario where I take pictures relatively fast (Raspberry Pi triggers the shutter), and sometimes the pictures get flushed out of the buffer before then end up on SD card. So, I would like to check the SD card's content upon every shutter release to be sure that picture is taken, so the mounting would be read-only, so maybe this can be done safely?
Maybe the answer is SD card extension cable?
I already have bought wireless Transcend SD card, but the polling for the directory's content is unreliable an can be slow.
Dmitry Grinberg, the person who hacked Transcend Wifi SD card claims that there is linux runnig on the SD card, and that SD's storage is simultaniously mounted by embedded linux runnig on SD and by digital camera (probably some kind of linux as well). He has his concerns about two devices mounting the same storage.
That is to say two operating systems (linux in the card and whatever is connected to it externally) both have the same FAT32 filesystem mounted read-write. If this does not scare you, it should - the external filesystem can cache reads and buffer writes at will, so no matter how clever the internal driver is, it can never have the whole picture. The lesson here is do NOT write to /mnt/sd without carefully considering the repercussions.
I am wondering if perhaps something similar could be done between raspberry pi and digital camera.