There are currently two main choices available for ident() callouts: one for CFI and another for non-CFI. Most modern flash chips support the common flash interface (CFI) specification, a common method of identifying a flash chip and its capabilities. If your flash chip supports CFI, then you should always use the CFI-specific ident() callout. The alternative is to use a hard-coded table of recognized flash IDs. These non-CFI-specific ident() callouts usually require some customization and should be used as a last resort.