I've not tried it, but why don’t you try using the system() function. If it is available you could run Linux commands in the IDE and you should be able to read and write into the SD card without any problems.
system() is tested to work fine.
The FAT partition is required for booting. It's also exposed as mass storage device via USB.
Rather than putting rootfs as a raw image file within the boot partition there is a 2nd ext4 partition for the rootfs.
Sure, I know I can access the SD using Linux commands through system(), but I'm porting to Galileo a project that I developed on Arduino and I'd like to keep it as much Arduino-compliant as possible in order to be able to deploy my library on both boards...
Using the original Yocto image I had no problem while accessing the SD fs through the SD library. If I run the same code on the IoT Yocto image the file can't be read. Anyway if there's no solution, I'll give a shot to the Linux-based way ...
OK, thanks for bringing this up. Hope I can find some time to look into it.
Ok thanks! Meanwhile I tested the Linux-based way and it works fine!