On Fri, 6 May 2005, Bryan Althouse wrote:
> All IDE drives should have the identical memory map. But, the kernel does
> not communicate directly with the drive, it communicates though an IDE host
> adaptor (which may have different implementations). If the host adaptor's
> memory map "matches" that of the IDE drive spec, then you consider it to be
> a "standard port layout"? Since my host adaptor will be implemented in an
> FPGA, if I give it the IDE memory map defined in ide.h, then your example
> code will be applicable.
>
> The memory map defined in ide.h makes sense to me (it seems to match the IDE
> drive memory map) until we get down to offset 6 (IDE_SELECT_OFFSET). From
> here down, I have trouble matching the #define names with the register
> names/descriptions from the IDE spec. Also, I am puzzled as to why there
> are 10 registers defined in ide.h when my IDE spec only shows 9. The IDE
> spec that I am referencing looks like this:
>
> CS0 CS1 DA2 DA1 DA0 READ WRITE
> A N 0 0 0 Data Data
> A N 0 0 1 Error Features
> A N 0 1 0 Sector Count Sector Count
> A N 0 1 1 Sector Number Sector Number
> A N 1 0 0 Cylinder Low Cylinder Low
> A N 1 0 1 Cylinder High Cylinder High
> A N 1 1 0 Device/Head Device/Head
> A N 1 1 1 Status Command
> N A 1 1 0 Alternate Status Device Control (IRQ en/dis)
>
>
> ide.h shows the following offsets:
>
> #define IDE_DATA_OFFSET (0)
> #define IDE_ERROR_OFFSET (1)
> #define IDE_NSECTOR_OFFSET (2)
> #define IDE_SECTOR_OFFSET (3)
> #define IDE_LCYL_OFFSET (4)
> #define IDE_HCYL_OFFSET (5)
> #define IDE_SELECT_OFFSET (6)
> #define IDE_STATUS_OFFSET (7)
> #define IDE_CONTROL_OFFSET (8)
> #define IDE_IRQ_OFFSET (9)
>
> Do you know of an IDE host adapter chipset which is standard? If someone
> knows of a part number, I could look up its datasheet. This would probably
> clear up my confusion. Thanks again!
This is not the direct `memory map' of the IDE drive's registers! It's an
indirect map, cfr. e.g.
#define IDE_DATA_REG (HWIF(drive)->io_ports[IDE_DATA_OFFSET])
So the actual register is found by looking up offset IDE_DATA_OFFSET in the
array HWIF(drive)->io_ports[].
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
