Auf 10.03.2011 22:55, Jordan Justen schrieb: > On Thu, Mar 10, 2011 at 13:37, Carl-Daniel Hailfinger > <c-d.hailfinger.devel.2...@gmx.net> wrote: > >> Auf 10.03.2011 05:51, Jordan Justen schrieb: >> >>> I have documented a simple flash-like device which I think could be >>> useful for qemu/kvm in some cases. (Particularly for allowing >>> persistent UEFI non-volatile variables.) >>> >>> http://wiki.qemu.org/Features/System_Flash >>> >>> Let me know if you have any suggestions or concerns. >>> >>> >> Is there any reason why you chose to invent an interface for the flash >> chip which is more complicated than the interface used by common flash >> chips out there? >> Maybe some EFI requirement? >> > This is a simpler version than the flash devices I'm used to dealing > with for x86/x86-64 UEFI systems. Can you suggest an alternative real > interface that is simpler? >
Pseudocode for the real interface most common on x86 before SPI came along: Write a page (256 bytes) or a few bytes: chip_writeb(0xAA, bios_base + 0x5555); chip_writeb(0x55, bios_base + 0x2AAA); chip_writeb(0xA0, bios_base + 0x5555); chip_writeb(databyte0, bios_base + addr); chip_writeb(databyte1, bios_base + addr + 1); chip_writeb(databyte2, bios_base + addr + 2); chip_writeb(databyte3, bios_base + addr + 3); ... up to 256 databytes. chip_readb(bios_base); The last chip_readb(bios_base) is repeated until the result does not change anymore. For me, that looks pretty simple and straightforward, especially compared to other more exotic flash chip interfaces. Regards, Carl-Daniel -- http://www.hailfinger.org/
