Re: [RFC PATCH 11/17] hw/sd: Add eMMC support

["Philippe Mathieu-Daudé via" <qemu-devel@nongnu.org>]

On 31/5/22 07:58, Cédric Le Goater wrote:
> On 5/30/22 19:40, Philippe Mathieu-Daudé wrote:
>> On 18/3/22 14:28, Cédric Le Goater wrote:
>>> The initial eMMC support from Vincent Palatin was largely reworked to
>>> match the current SD framework. The parameters mimick a real 4GB eMMC,
>>> but it can be set to various sizes.
>>>
>>> This adds a new QOM object class for EMMC devices.
>>>
>>> Signed-off-by: Vincent Palatin <vpalatin@chromium.org>
>>> Link: 
>>> https://lore.kernel.org/r/1311635951-11047-5-git-send-email-vpalatin@chromium.org 
>>>
>>> [ jms: - Forward ported to QEMU 5.2 ]
>>> Signed-off-by: Joel Stanley <joel@jms.id.au>
>>> [ clg: - ported on aspeed-7.0 patchset
>>>         - HPI activation ]
>>> Signed-off-by: Cédric Le Goater <clg@kaod.org>
>>> ---
>>>   hw/sd/sdmmc-internal.h |  97 +++++++++++++++++++
>>>   include/hw/sd/sd.h     |   9 ++
>>>   hw/sd/sd.c             | 205 ++++++++++++++++++++++++++++++++++++++++-
>>>   hw/sd/sdmmc-internal.c |   2 +-
>>>   4 files changed, 311 insertions(+), 2 deletions(-)
>>
>>
>>> +static void emmc_class_init(ObjectClass *klass, void *data)
>>> +{
>>> +    DeviceClass *dc = DEVICE_CLASS(klass);
>>> +    SDCardClass *sc = SD_CARD_CLASS(klass);
>>> +
>>> +    dc->desc = "eMMC";
>>> +    sc->proto = &sd_proto_emmc;
>>> +    sc->spec_version = SD_PHY_SPECv3_01_VERS; /* eMMC requirement */
>>> +    sc->set_csd = sd_emmc_set_csd;
>>> +}
>>> +
>>> +static const TypeInfo emmc_info = {
>>> +    .name = TYPE_EMMC,
>>> +    .parent = TYPE_SD_CARD,
>>
>> Hmm this is odd to have the model inheriting features from SD_CARD but 
>> then behaving differently (one could enumerate QDEV objects implementing
>> TYPE_SD_CARD then use them expecting they match the SD card protocol).
>>
>> Why do you need to have TYPE_SD_CARD as parent?
> 
> Simply for the initialization.
>> Could we simply duplicate sd_class_init() assignations instead? That
>> would likely make it easier to modify eMMC handlers.
> 
> May be we lack a base abstract class ?

I've been thinking about it but maybe not enough. I'll revisit.

> It would clean up this section in the realize routine :
> 
>     sd->proto = sd->spi ? &sd_proto_spi : &sd_proto_sd;
> 
>      if (sc->proto) {
>          sd->proto = sc->proto;
>      }

In v2 I moved the 'proto' field from instance to class, so we don't need
this hack anymore.