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Re: [Qemu-devel] [RFC] ide: multi-profile DVD-ROM support v2.1

From: Thiemo Seufer
Subject: Re: [Qemu-devel] [RFC] ide: multi-profile DVD-ROM support v2.1
Date: Tue, 8 Jan 2008 14:42:11 +0000
User-agent: Mutt/1.5.17 (2007-11-01)

Carlo Marcelo Arenas Belon wrote:
> This is version 2.1 of the patch to re-implement the "GET CONFIGURATION"
> MMC-6 command as used by the IDE emulation to match the published SPEC
> and that was originally published in :
>   http://lists.gnu.org/archive/html/qemu-devel/2007-11/msg00849.html
> Important changes from the previous patches :
> * Use a 99min CD size as the bigger possible sector count for CD profile
> * Don't recalculate the number of sectors
> * Use an inline helper function to set the profiles in a cleaner way
> * Avoid extra computations from constants except for #define values
> * Reduce the use of magic numbers and use defines when possible
> Remaining issues that will need to be addressed in future versions :
> * MMC-6 also applies to SCSI devices and so the definitions might need
>   to be moved to a common header when that code is developed.
> * The use of the buffer might not be safe for unaligned access in some
>   architectures, but the same applies to all other commands that are
>   currently using the io_buffer directly as the hardware does.
> * The heuristic used tries to guess the kind of media from the size of
>   it and is not that reliable for really small DVDs that could fit in a
>   CD.
> * The response uses the io_buffer and is therefore limited to the size
>   of it (not really a problem now when the maximum response size will
>   be 20 bytes) but could be a problem when more features/profiles are
>   implemented.
> * When using the host_device driver media changes could go unnoticed
>   and result in the wrong profile being selected due to limitations
>   in the current implementation of the ide emulation.

Please add those caveats as comments to the source code.


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