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Re: [Qemu-devel] [PATCH] ahci: SATA FIS is 20 bytes, not 0x20
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From: |
Kevin Wolf |
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Subject: |
Re: [Qemu-devel] [PATCH] ahci: SATA FIS is 20 bytes, not 0x20 |
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Date: |
Wed, 23 May 2012 12:04:03 +0200 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1 |
Am 23.05.2012 11:53, schrieb Alexander Graf:
>
>
> Am 23.05.2012 um 11:13 schrieb Kevin Wolf <address@hidden>:
>
>> Am 23.05.2012 01:26, schrieb Daniel Verkamp:
>>> As in the SATA and AHCI specifications, a FIS is 5 Dwords of 4 bytes
>>> each, which comes to 20 bytes (decimal), not 0x20.
>
> Not sure I understand. FISs can have different sizes depending on the payload
> they are. The one you are looking at here is the d2h init FIS.
>
> From the SATA 1.0a spec:
>
> FIS Type - Set to a value of 34h. Defines the rest of the FIS fields. Defines
> the length of the
> FIS as five Dwords.
>
> So yes, you are right. The register FIS is 20 bytes, not 0x20 bytes long.
>
> Does this fix some actual breakage for you?
In theory the SDBFIS could be overwritten with zeros. No idea what this
means or if it matters in practice.
Kevin