[RFC PATCH 1/3] fastboot: Allow runtime determination of MMC device

Simon Glass sjg at chromium.org
Thu May 27 15:44:17 CEST 2021

Hi Andre,

On Sun, 23 May 2021 at 18:37, Andre Przywara <andre.przywara at arm.com> wrote:
> At the moment the fastboot code relies on the Kconfig variable
> CONFIG_FASTBOOT_FLASH_MMC_DEV to point to the MMC device to use for the
> flash command. This value needs to be the *U-Boot device number*, which
> recently got more dynamic, and depends on other MMC nodes in the
> devicetree, but also on mmc aliases defined. This leads to situations
> where it's hard to fix this number at compile time, because a WiFi
> device might enumerate before the wanted eMMC device, for instance.
> To avoid this fragile situation, allow this value to be determined at
> runtime. This decision is probably platform specific, so introduce a
> weak function that returns the needed number, and use that everywhere
> instead of the Kconfig variable.
> For now the default implementation just returns this very Kconfig
> variable, but this can be overwritten by platforms later.
> No functional change at this point.
> Signed-off-by: Andre Przywara <andre.przywara at arm.com>
> ---
>  drivers/fastboot/fb_command.c |  6 +++---
>  drivers/fastboot/fb_common.c  |  3 ++-
>  drivers/fastboot/fb_mmc.c     | 12 ++++++++----
>  include/fastboot.h            |  7 +++++++
>  4 files changed, 20 insertions(+), 8 deletions(-)

I wonder if this would be better done using a sysinfo driver? Then it
could be hard-coded, picked up from the DT, probed at runtime, etc.,
just as with a weak function.


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