linux-kernel - Re: [PATCH v5 5/7] dax: Introduce dax_cxl

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Message-ID: <aXkaDbpeqtABP3y7@aschofie-mobl2.lan>
Date: Tue, 27 Jan 2026 12:03:25 -0800
From: Alison Schofield <alison.schofield@...el.com>
To: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
CC: <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
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Subject: Re: [PATCH v5 5/7] dax: Introduce dax_cxl_mode for CXL coordination

On Thu, Jan 22, 2026 at 04:55:41AM +0000, Smita Koralahalli 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.

same as DaveJ comment. Fold into next patch that uses it and grow the
explanation of the state machine in that commit log. Also add in
code comments to this enum.

> 
> No functional changes.
> 
> Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@....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 {
> +	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) \
> -- 
> 2.17.1
>