[SPI Flash] Add interface to fetch flash size

[mizhka]

Summary

Right now there is no way to fetch serial flash size. To fix it, new
interface is proposed and implementation for known serial flash
implementations: mx25l and at45d

Test Plan

Tested on ASUS RT-N53 (SPI flash) and ASUS RT-N16 (CFI flash)

[adrian]

Wait, why can't we get the size via a GEOM call?

[mizhka]

In D6243#132906, @adrian wrote:

Wait, why can't we get the size via a GEOM call?

I'm newbie with geom, but geom_flashmap fetches device_t from consumer and pass it to callback. So there is only information about device_t in slicer function callback.

But I think it's easy to implement geom_disk function to fetch disk by device softc. Is it similar to what you expect?

Thanks!

[mizhka]

In D6243#132906, @adrian wrote:

Wait, why can't we get the size via a GEOM call?

D6400 to add geom call for this purpose

[mizhka]

I would like to resurrect this revision due to new discovered issues. WiFi & ethernet drivers requires information from NVRAM which is part of flash device. To scan & parse it, we need to know flash size before GEOM is initialized.

So we need this flash interface to fetch sizing.

[adrian]

hi warner,

Michael requests this so he can get the flash size for doing SPROM parsing before GEOM is up (ie, very very early in device boot.) How's this look?

[mizhka]

Hi Warner

Could you have a look at this revision?

Thank you in advance

(to trigger notifications: @imp @adrian )