Re: [PATCH v5 5/7] dax: Introduce dax_cxl_mode for CXL coordination

[Jonathan Cameron <jonathan.cameron@huawei.com>]

On Thu, 22 Jan 2026 04:55:41 +0000
Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com> wrote:

> Introduce dax_cxl_mode to coordinate between dax_cxl and dax_hmem when
> handling CXL tagged memory ranges.
> 
> This patch defines the dax_cxl_mode enum and establishes a default policy.
> Subsequent patches will wire this into dax_cxl and dax_hmem to decide
> whether CXL tagged memory ranges should be deferred, registered or
> dropped.
> 
> No functional changes.
> 
> Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>
> ---
>  drivers/dax/bus.c | 3 +++
>  drivers/dax/bus.h | 8 ++++++++
>  2 files changed, 11 insertions(+)
> 
> diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
> index fde29e0ad68b..72bc5b76f061 100644
> --- a/drivers/dax/bus.c
> +++ b/drivers/dax/bus.c
> @@ -24,6 +24,9 @@ DECLARE_RWSEM(dax_region_rwsem);
>   */
>  DECLARE_RWSEM(dax_dev_rwsem);
>  
> +enum dax_cxl_mode dax_cxl_mode = DAX_CXL_MODE_DEFER;
> +EXPORT_SYMBOL_GPL(dax_cxl_mode);
> +
>  #define DAX_NAME_LEN 30
>  struct dax_id {
>  	struct list_head list;
> diff --git a/drivers/dax/bus.h b/drivers/dax/bus.h
> index cbbf64443098..a40cbbf1e26b 100644
> --- a/drivers/dax/bus.h
> +++ b/drivers/dax/bus.h
> @@ -41,6 +41,14 @@ struct dax_device_driver {
>  	void (*remove)(struct dev_dax *dev);
>  };
>  
> +enum dax_cxl_mode {
I'd suggest kernel-doc for these. Their meaning isn't entirely obvious
from the names.

> +	DAX_CXL_MODE_DEFER,
> +	DAX_CXL_MODE_REGISTER,
> +	DAX_CXL_MODE_DROP,
> +};
> +
> +extern enum dax_cxl_mode dax_cxl_mode;
> +
>  int __dax_driver_register(struct dax_device_driver *dax_drv,
>  		struct module *module, const char *mod_name);
>  #define dax_driver_register(driver) \