Novena/EEPROM

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Revision as of 09:36, 12 October 2014 by Xobs (talk | contribs) (Feature bitmask)
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Novena has a utility EEPROM that can be used for storing device-specific data. This is optional, and default values will be used if it is blank / not present.

All multi-byte integers are in native host order.

Version 1 structure

EEPROM structure
Size Default Value Description Result if no EEPROM present
6 'Novena' Unterminated EEPROM signature The EEPROM contents will not be used
1 1 Version number of EEPROM structure The EEPROM contents will not be used
1 0 Reserved No change
4 0 Device serial number No change
6 (Random) Gigabit MAC address Random MAC address is generated on each boot
2 0 Feature bitmask No features are enabled

Version 2 structure

The actual structure is defined in novena-eeprom.h as "struct novena_eeprom_data".

EEPROM structure
Size Default Value Description Result if no EEPROM present
6 'Novena' Unterminated EEPROM signature The EEPROM contents will not be used
1 2 Version number of EEPROM structure The EEPROM contents will not be used
1 32 Length of EEPROM read/write page EEPROMOops may not be able to properly save panics
4 0 Device serial number No change
6 (Random) Gigabit MAC address Random MAC address is generated on each boot
2 0 Feature bitmask No features are enabled
4 0 LVDS channel 1 frequency No display
2 0 LVDS channel 1 display width No display
2 0 LVDS channel 1 display height No display
2 0 LVDS channel 1 horizontal back porch No display
2 0 LVDS channel 1 horizontal front porch No display
2 0 LVDS channel 1 horizontal sync length No display
2 0 LVDS channel 1 vertical back porch No display
2 0 LVDS channel 1 vertical front porch No display
2 0 LVDS channel 1 vertical sync length No display
4 0 LVDS channel 1 flags (see below) No display
4 0 LVDS channel 2 frequency No display
2 0 LVDS channel 2 display width No display
2 0 LVDS channel 2 display height No display
2 0 LVDS channel 2 horizontal back porch No display
2 0 LVDS channel 2 horizontal front porch No display
2 0 LVDS channel 2 horizontal sync length No display
2 0 LVDS channel 2 vertical back porch No display
2 0 LVDS channel 2 vertical front porch No display
2 0 LVDS channel 2 vertical sync length No display
4 0 LVDS channel 2 flags (see below) No display
4 0 HDMI default frequency No display
2 0 HDMI default display width No display
2 0 HDMI default display height No display
2 0 HDMI default horizontal back porch No display
2 0 HDMI default horizontal front porch No display
2 0 HDMI default horizontal sync length No display
2 0 HDMI default vertical back porch No display
2 0 HDMI default vertical front porch No display
2 0 HDMI default vertical sync length No display
4 0 HDMI default flags (see below) No display
4 4096 EEPROM capacity (in bytes) No change
4 4096 EEPROMoops offset (in bytes) EEPROMoops support will be disabled
4 61440 EEPROMoops length (in bytes) EEPROMoops support will be disabled

Feature bitmask

There is a bitmask field that defines various board features. In this way, a single image can be shipped that supports various components. For example, a router might not have a display, but a laptop would need to have its LCD turned on. A bit is "1" if the feature is present (and needs to be enabled), and "0" if it is not present. Note that some values are mutually-exclusive (e.g. you can only have one kind of LVDS display attached).

Feature list
Bit position Mask Feature
0 0x0001 ES8328 Audio Codec
1 0x0002 Senono-based battery board
2 0x0004 Retina LVDS display (flag ignored in version 2)
3 0x0008 (Reserved: Other LVDS display)
4 0x0010 mPCIe port
5 0x0020 Gigabit Ethernet
6 0x0040 HDMI Output (flag ignored in version 2)
7 0x0080 Root is on SATA (if 0, root is on internal MMC)

LVDS/HDMI flags bitmask

Feature list
Bit position Mask Feature
0 0x0001 Channel is present
1 0x0002 If 1, use both LVDS channels together
2 0x0004 Polarity of vsync signal
3 0x0008 Polarity of hsync signal
4 0x0010 1 if LVDS is JEIDA mapping, 0 if it's PSWG/SWPG
5 0x0020 1 if data is 8-bit (24 bpp), 0 if it's 6-bit (18 bpp)