On Fri, Dec 04, 2015 at 10:50:21AM -0800, Peter Crosthwaite wrote: > > FWIW, I don't think the SD card will be qdevified because it doesn't > > need a bus. It's similar indeed to SerialState, which was supposed to > > be the poster child of QOM embedding and never got QOMified. > > SD is a bus in its own right and should be busified and QOMified IMO. > SDHCI can talk to non-sd cards (SDIO). There is also a range of > incompatible cards that you can talk to - MMC/eMMC/SD(H|S|X)C. I think > anything that couples the controller to an SD card is a bug, the card > and device should be arranged as separate devices. > > > A host controller controls exactly one SD card, the SSI bridge is also > > for exactly one SD card, etc. > > I think you can RYO chip selects with a GPIO and control multiple SD > cards with one SDHCI.
In practice, the SDHCI controllers are one-to-one with cards. This is codified in the sdhci spec as it has a "card present" bit and "port location" information that is per controller. I suppose in theory, one could put an SDHCI contoller into SPI compatibility mode and "hot wire" it into a bus, but qemu doesn't support that anyway, and it is a lot of complexity for something that is not done in practice. -Kevin
