On 4/10/24 15:44, Tom Rini wrote:
On Wed, Apr 10, 2024 at 07:27:17PM +0200, Heinrich Schuchardt wrote:
Am 10. April 2024 19:06:57 MESZ schrieb Caleb Connolly caleb.connolly@linaro.org:
Introduce support for a uclass to provide a fallback/stub driver which can be used when no device is found for a given node. This might be useful for handling non-essential clock controllers like the RPMh on Qualcomm platforms, or during early bringup to get UART output before a real clock driver has been created.
Signed-off-by: Caleb Connolly caleb.connolly@linaro.org
drivers/core/Kconfig | 10 ++++++++++ drivers/core/uclass.c | 24 +++++++++++++++++++++++- include/dm/uclass.h | 3 +++ 3 files changed, 36 insertions(+), 1 deletion(-)
diff --git a/drivers/core/Kconfig b/drivers/core/Kconfig index 1081d61fcf01..09075b9b7a15 100644 --- a/drivers/core/Kconfig +++ b/drivers/core/Kconfig @@ -466,5 +466,15 @@ config BOUNCE_BUFFER
A second possible use of bounce buffers is their ability to provide aligned buffers for DMA operations.+menuconfig FALLBACK_DRIVERS
Wouldn't it be preferable to mark individual drivers as fallback drivers in their declaration?
This would allow alternative fallback drivers and would not require any definitions at uclass level.
Just by building a fallback driver you would enable the fallback behavior for its uclass.
I think some of this is addressed in the cover letter. My concern / questions come down to I think just a matter of naming. Both "fallback" and "stub" are used at times. As a concept, we have some areas where we need a no-op driver because whereas the DT describes a relationship in the hardware, here in U-Boot we can just accept things as configured. To me "fallback" implies more functionality of the driver when it's really just a generic no-op driver to fill in the dependencies within the tree. Can we rename things a bit along those lines?
I would rather just have a stub driver with compatibles for all clocks we want it to match. I think having a generic fallback driver could cause issues in the future if we need to switch over to using a real driver.
--Sean