Why do reads from the last byte address on my EPCQ device fail?

Description

Due to a problem in the Altera Nios® II HAL driver for the Altera EPCQ IP, you may be not be able to read the last byte of EPCQ devices using the following command:
alt_read_flash (fd, 0xFFFFFF, ch, 1);  where  (0xFFFFFF is last byte address of EPCQ)

The function will error with a return value off -22 when reading last byte of EPCQ. (If the command is successful, the return value is 0).

Resolution

The Nios II HAL driver for the code of the EPCQ driver has a variable called end_address. This variable was incorrectly assumed non-inclusive.

To fix this problem:

In the Quartus® Prime software 15.0 and above change line 730,  In Quartus Prime software
14.1 and below change line 611 as follows to remove the = in the compare:

 end_address > epcq_flash_info->data  

This problem is scheduled to be fixed in a future release of the Quartus software.