vfs/fs_stat: set st_size on EEPROM character drivers

[ajuckler]

Summary

The NuttX documentation states that it is possible to use an EEPROM character driver with a file system by converting it to a block device using the loop device (losetup). However, losetup() fails with message File is too small for blocksize because the st_size field is not populated by the stat() function when used on character drivers.

This MR fixes this error by:

• Allowing to retrieve the geometry of an EEPROM character driver using ioctl;
• Using this geometry to populate the st_size field on stat().

Impact

The eeprom_25xx_e enum contents have changed due to the addition of the sector size.

Testing

Tested on a custom target (STM32F7-based) with a Rhom BR25G256FVT EEPROM (equivalent to a Microchip 25xx256).

Following piece of code would fail before the changes in fs_stat:

ee25xx_initialize(spi_p, "/dev/ee25xx", EEPROM_25XX256, 0);
losetup("/dev/ee25blk", "/dev/ee25xx", 64, 0, 0);

[acassis]

@ajuckler I approved assuming you will submit the requested Documentation/

[acassis]

Pretty good Documentation! Thank you!

[ajuckler]

@acassis @xiaoxiang781216
I've just pushed a fix to the g_ee25xx_devices definition.
The location of the newly added sector size was wrong, I didn't notice it until now because I was not checking if a read call was returning what has been previously written.

The following has been tested on spi_xx25xx (in addition to the losetup):

• Retrieving the geometry using IOCTL
• Writing data at a fixed non-zero offset
• Reading back the written data