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On Thursday 19 April 2007 03:53, Iain Buchanan wrote: |
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> > > hda: 39070080 sectors (20003 MB) w/1740KiB Cache, |
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> > > CHS=16383/255/63<6>hda: hw_config=600d, UDMA(100) |
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> > > |
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> > > What's the hw_config part? |
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> > |
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> > Any more (useful) ideas on this? |
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Seems a kind of hardware config register (part of a struct hd_driveid |
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object), whose value is used by the ide drivers to adjust the drive |
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speed, depending on the type of cable used. The function that checks its |
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value (and prints the "hda: hw_config=600d" message you are seeing) |
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seems to be in drivers/ide/ide-iops.c, and is defined as follows: |
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/* |
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* All hosts that use the 80c ribbon must use! |
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* The name is derived from upper byte of word 93 and the 80c ribbon. |
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*/ |
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u8 eighty_ninty_three (ide_drive_t *drive) |
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That function is called from various pci ide drivers code (for example |
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drivers/ide/pci/it821x.c, drivers/ide/pci/siimage.c, |
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drivers/ide/pci/piix.c, drivers/ide/pci/sis5513.c), from a function |
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whose name is composed appending "_ratemask" to the driver name (eg, |
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piix_ratemask, sis5513_ratemask, etc.) in a way similar to this: |
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if (!eighty_ninty_three(drive)) |
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mode = min(mode, (u8)1); |
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So, if eighty_ninty_three returns 0, "mode" (which I suppose indicates |
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the DMA/UDMA mode) is set to 1 if it wasn't already. |
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This value is then used as an argument to the ide_rate_filter function |
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(along with the xferspeed). The comments in the code for ide_rate_filter |
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are as follows (drivers/ide/ide-lib.c): |
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/** |
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* ide_rate_filter - return best speed for mode |
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* @mode: modes available |
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* @speed: desired speed |
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* |
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* Given the available DMA/UDMA mode this function returns |
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* the best available speed at or below the speed requested. |
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*/ |
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Bottom line: the message you see is an informational message printed |
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during ide initialization, and the value of hw_config is used by the |
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kernel to set drive speed. |
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Keep in mind that I'm definitely no kernel guru, and did my searches by |
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simply grepping through the code, so something might be wrong in what I |
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said. Anyway, I think the general idea is correct. |
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But don't worry, because your value for hw_config is "600d"! :) |
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-- |
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