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Re: [PATCH v2 01/13] hw/sd/ssi-sd: Do not create SD card within controll

From: Peter Maydell
Subject: Re: [PATCH v2 01/13] hw/sd/ssi-sd: Do not create SD card within controller's realize
Date: Mon, 6 Dec 2021 13:05:26 +0000

On Mon, 6 Dec 2021 at 12:35, Markus Armbruster <armbru@redhat.com> wrote:
> Philippe Mathieu-Daudé <f4bug@amsat.org> writes:
> > I guess a already asked this once but don't remember now... What is the
> > point of creating a SD card without drive? Is this due to the old design
> > issue we hotplug the drive to the SD card and not the SD card on the SD
> > bus?
> Device model "sd-card" implements BlockdevOps method change_media_cb().
> This menas it models a device with a removable medium.  No drive behaves
> like no medium.  I guess it's an SD card reader.

No, device sd-card really is the SD card -- the protocol between
the SD controller device and the sd-card device is (a slightly
abstracted version of) the protocol that goes between the card
and the controller in hardware. I think the reason it's implemented
as a "device with a removable medium" is historical -- back in
2007 that was the only way to support runtime ejecting and
insertion. We'd implement it differently today, but we've wanted
to preserve the user-facing compatibility of how the monitor
commands for ejecting and inserting an sd card work.

(Side note, the initial sd implementation actually tells the block
layer that it's BDRV_TYPE_FLOPPY as a "reasonable approximation"...)

-- PMM

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