vfs_fat_link opened two files to perform copy operation. File structures
were allocated on the stack. When _MAX_SS setting was increased in
ffconf.h due to wear levelling feature, the size of these structures
increased to ~4k each (~8k total). This exceeds stack size allocated for
tasks in most typical cases.
This change makes file structures dynamically allocated.
Originally, prepend_drive_to_path was designed to be a macro, and it
modified local path variables to point to a temporary buffers.
When it was converted into a function, modification to path variables
were no longer visible outside of this function.
In addition to that, prepend_drive_to_path allocated 2k bytes on the
stack for temporary path buffers. This is replaced with path buffers
allocated as part of vfs_fat context object. Locking is added around
parts of code which use these temporary buffers.
Additionally, _lock member of vfs_fat_ctx_t was placed after the
variable-sized files array, which caused the first entry in the
array to be never used. This change fixes the order of members
and adds comments.
FATFS enable support for multiple drives
Current implementation has drive numbers and paths hardcoded to support
only one FATFS drive. Arduino has it's own SPI driver to allow
compatibility and flexibility. With the MR it is possible to have up to
```_VOLUMES``` drives connected (SPI, SDMMC and others) at the same
time and accessed through VFS
See merge request !478
Current implementation has drive numbers and paths hardcoded to support
only one FATFS drive. Arduino has it's own SPI driver to allow
compatibility and flexibility. With the MR it is possible to have up to
```_VOLUMES``` drives connected (SPI, SDMMC and others) at the same
time and accessed through VFS
