Re: [Qemu-devel] [RFC PATCH] ssi-sd: Make devices picking up backends unavailable with -device

[Philippe Mathieu-Daudé]

Hi Markus,

On 9/26/18 11:00 AM, Markus Armbruster wrote:
> Device models aren't supposed to go on fishing expeditions for
> backends.  They should expose suitable properties for the user to set.
> For onboard devices, board code sets them.
> 
> Device ssi-sd picks up its block backend in its init() method with
> drive_get_next() instead.  This mistake is already marked FIXME since
> commit af9e40a.
> 
> Unset user_creatable to remove the mistake from our external
> interface.  Since the SSI bus doesn't support hotplug, only -device
> can be affected.  Only certain ARM machines provide an SSI bus.

There is also a MicroBlaze machine.

Note that out of those target, we could model SSI buses on
southbridges/LPC devices but there is no interest.

I'm also spending some hobby time on a MIPS SoC which exposes a SSI bus.

> Signed-off-by: Markus Armbruster <address@hidden>
> ---
> Are there valid uses of -device ssi-sd?  If no, this patch is fine.
> If yes, this patch breaks them.  But fixing the FIXME will also break
> them.  What should we do?

This device was probably orphan (not used) for a long time, and seems
unusable in it current state to me, see:
http://lists.nongnu.org/archive/html/qemu-devel/2018-06/msg01757.html

I have to address Peter's comment to my patch noted in my TODO (low
priority), so I'm OK to get ride of the FIXME.

I suppose it is easier for you to get your patch in, then let me clean
that later.

Regards,

Phil.

> 
>  hw/sd/ssi-sd.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/hw/sd/ssi-sd.c b/hw/sd/ssi-sd.c
> index 95a143bfba..ec7c7e6dbf 100644
> --- a/hw/sd/ssi-sd.c
> +++ b/hw/sd/ssi-sd.c
> @@ -284,6 +284,8 @@ static void ssi_sd_class_init(ObjectClass *klass, void 
> *data)
>      k->cs_polarity = SSI_CS_LOW;
>      dc->vmsd = &vmstate_ssi_sd;
>      dc->reset = ssi_sd_reset;
> +    /* Reason: init() method uses drive_get_next() */
> +    dc->cannot_instantiate_with_device_add_yet = true;
>  }
>  
>  static const TypeInfo ssi_sd_info = {
>