[GTALUG] long war story: growing the ESP (/boot/efi)

[D. Hugh Redelmeier]

| From: Trevor Woerner via talk <talk at gtalug.org>

| On Thu 2021-07-15 @ 10:37:03 AM, D. Hugh Redelmeier via talk wrote:

| > NAND flash

| > - erases can only be done in large blocks.  The size of these blocks is
| >   generally secret but I think that they are in the range of 128KiB to
| >   1MiB.
| 
| The size of the erase block is *always* stated in each device's datasheet.
| Otherwise how else would we be able to configure the SoC's NAND controller? An
| SoC's NAND controller needs to know the size of the erase block in order to
| work with the NAND correctly.

This is not the case for flash that is included in ordinary PCs.
Well, it might be the case for SPI flash, but the OS generally doesn't
deal with it.

The flash devices we buy for the PC world are

- USB flash memory stick (lots of firmware between out OS and the flash)

- SD cards and the like (including eMMC) (looks like a disk; commands
  are ATA / SCSI)

- SATA flash SSD (the OS sees a SATA HDD with a very few
  enhancements)

- m.2 / NVMe flash SSD (again, the OS sees an HDD as far as I know)

In each case, the device hides behind a controller and the
characteristics of the raw flash chips is not specified by the package
manufacturer.

As you point out, the embedded world has more choices, some of which are raw flash.