[U-Boot] U-boot Driver Model - MMC - missing uclass implementation?

[Philipp Rossak]

Hi,

I would like to develop an mmc driver for the STM32 boards with the new
driver model.

I already built up the basic structure and I discovered some strange
behaviour compared to net or serial drivers:

When I place only the following statement in the driver .c file:

U_BOOT_DRIVER(sdhci_stm32) = {
    .name        = "stm32_sdhci",
    .id              = UCLASS_MMC,
    .ops           = &stm32_mmc_ops,
    .probe        = stm32_mmc_probe,
...
};

I receive the following Message when i perform the "dm uclass" command in
u-boot:

Cannot find uclass for id 31: please add the UCLASS_DRIVER() declaration
for this UCLASS_... id

But when I had a look at the sources, i found some UCLASS_DRIVER()
declaration in drivers/mmc/mmc-uclass.c for the mmc driver.

The driver is copied from the sandbox_mmc driver. I only renamed the
functions and added some debug messages.

When i add this statement to my driver:

UCLASS_DRIVER(sdhci_stm32) = {
    .name        = "stm32_sdhci",
    .id        = UCLASS_MMC,
};

And I perform the dm uclass command in u-boot i receive the following:

uclass 31: stm32_sdhci

Do you have any idea what i'm doing wrong / what i missed?

Is there maybe some UCLASS implementation missing or not linked?

Best,
Philipp