Re: [Qemu-devel] [PATCH 0/3] Drop default SD card creation

[Markus Armbruster]

Peter Maydell <address@hidden> writes:

> On 16 August 2012 15:11, Markus Armbruster <address@hidden> wrote:
>> Peter Maydell <address@hidden> writes:
>>> As suggested in the recent discussion on Markus' patchset to suppress
>>> unused default drives, this patchset cleans up the omap and pxa2xx
>>> SD card controllers to behave like the other controllers:
>>>  * the init function looks for the next IF_SD drive
>>>  * if there isn't one, we start up as a controller with no card
>>>    present
>
>> Isn't this an incompatible change?  Before, you get an SD card reader
>> backed by an empty BDS default.  You can load/unload cards in the
>> monitor.  After, you get an SD card reader that isn't backed by a BDS by
>> default.  Device models prepared for that can treat it as permanently
>> empty.
>
> Hmm, yes, but most of our SD controllers already act that way.
> We should probably fix them all...
>
> So what's the block layer equivalent of drive_get_next() that always
> returns us something we can get a bdrv from?

I figure you need a variant of drive_get(type, bus, unit) that creates
and returns a default drive instead of null when

1. the user didn't suppress default drives with -nodefaults, and

2. (type, index) are (IF_FLOPPY, 0), (use_scsi ? IF_SCSI : IF_IDE, 2),
or (IF_SD, 0), where index satisfies drive_index_to_bus_id(type, index)
== bus and drive_index_to_unit_id(type, index) == unit.

Happy coding :)


PS: I hate drive_get_next(), because it makes which device model gets
which drive depend on initialization order.