Re: [PATCH v4 07/12] drm/xe/pat: Return error from xe_pat_init_early() on unknown platform

["Mallesh, Koujalagi" <mallesh.koujalagi@intel.com>]

On 28-09-2026 02:51 pm, Dnyaneshwar Bhadane wrote:
> xe_pat_init_early() currently only logs an error when the platform's
> graphics version doesn't match any known PAT table, but continues
> probing with an uninitialized pat.ops. This can lead to a NULL
> pointer dereference later when pat.ops is used.
>
> Change xe_pat_init_early() to return an int and propagate -ENODATA
> to xe_device_probe() so the driver fails to load cleanly instead of
> continuing in a broken state.
>
> Fixes: 152d7f2db978 ("drm/xe/pat: Handle unicast vs MCR PAT registers")
> Signed-off-by: Dnyaneshwar Bhadane <dnyaneshwar.bhadane@intel.com>
LGTM,
Reviewed-by: Mallesh Koujalagi <mallesh.koujalagi@intel.com>
> ---
> v2:
>   - Update kernel-doc for xe_pat_init_early. (Michal)
> ---
> ---
>   drivers/gpu/drm/xe/xe_device.c |  4 +++-
>   drivers/gpu/drm/xe/xe_pat.c    | 13 ++++++++++++-
>   drivers/gpu/drm/xe/xe_pat.h    |  4 +++-
>   3 files changed, 18 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
> index 44975e7823be..327f018fe15e 100644
> --- a/drivers/gpu/drm/xe/xe_device.c
> +++ b/drivers/gpu/drm/xe/xe_device.c
> @@ -879,7 +879,9 @@ int xe_device_probe(struct xe_device *xe)
>   	int err;
>   	u8 id;
>   
> -	xe_pat_init_early(xe);
> +	err = xe_pat_init_early(xe);
> +	if (err)
> +		return err;
>   
>   	err = xe_sriov_init(xe);
>   	if (err)
> diff --git a/drivers/gpu/drm/xe/xe_pat.c b/drivers/gpu/drm/xe/xe_pat.c
> index a5fe1beec652..519f7d5a2765 100644
> --- a/drivers/gpu/drm/xe/xe_pat.c
> +++ b/drivers/gpu/drm/xe/xe_pat.c
> @@ -590,7 +590,13 @@ static const struct xe_pat_ops xe3p_xpc_pat_ops = {
>   	.entry_dump = xe3p_xpc_pat_entry_dump,
>   };
>   
> -void xe_pat_init_early(struct xe_device *xe)
> +/**
> + * xe_pat_init_early() - Init early pat table operation.
> + * @xe: the &xe_device
> + *
> + * Return: 0 on success or a negative error code on failure.
> + */
> +int xe_pat_init_early(struct xe_device *xe)
>   {
>   	xe->pat.idx[XE_CACHE_WB_COMPRESSION] = XE_PAT_INVALID_IDX;
>   	xe->pat.idx[XE_CACHE_NONE_COMPRESSION] = XE_PAT_INVALID_IDX;
> @@ -686,14 +692,19 @@ void xe_pat_init_early(struct xe_device *xe)
>   		 * raise an error rather than trying to silently inherit the
>   		 * most recent platform's behavior.
>   		 */
> +
>   		drm_err(&xe->drm, "Missing PAT table for platform with graphics version %d.%02d!\n",
>   			GRAPHICS_VER(xe), GRAPHICS_VERx100(xe) % 100);
> +		return -ENODATA;
> +
>   	}
>   
> +	xe_assert(xe, xe->pat.ops);
>   	xe_assert(xe, xe->pat.ops->dump);
>   	xe_assert(xe, xe->pat.ops->program_graphics);
>   	xe_assert(xe, MEDIA_VER(xe) < 13 || xe->pat.ops->program_media);
>   	xe_assert(xe, GRAPHICS_VER(xe) < 20 || xe->pat.ops->entry_dump);
> +	return 0;
>   }
>   
>   void xe_pat_init(struct xe_gt *gt)
> diff --git a/drivers/gpu/drm/xe/xe_pat.h b/drivers/gpu/drm/xe/xe_pat.h
> index 7060f66e1d63..6398c3ab4805 100644
> --- a/drivers/gpu/drm/xe/xe_pat.h
> +++ b/drivers/gpu/drm/xe/xe_pat.h
> @@ -42,8 +42,10 @@ struct xe_pat_table_entry {
>   /**
>    * xe_pat_init_early - SW initialization, setting up data based on device
>    * @xe: xe device
> + *
> + * Return: 0 on success or a negative error code on failure.
>    */
> -void xe_pat_init_early(struct xe_device *xe);
> +int xe_pat_init_early(struct xe_device *xe);
>   
>   /**
>    * xe_pat_init - Program HW PAT table