Re: [PATCH] drm/xe/xe_late_bind_fw: Initialize uval variable in xe_late_bind_fw_num_fans()

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Wed, Oct 01, 2025 at 06:39:33AM +0530, mallesh.koujalagi@intel.com wrote:
> From: Mallesh Koujalagi <mallesh.koujalagi@intel.com>
> 
> Initialize the uval variable to 0 in xe_late_bind_fw_num_fans() to fix
> a potential use of uninitialized variable warning and ensure predictable
> behavior.
> 
> The variable is passed by reference to xe_pcode_read() which should
> populate it on success, but initializing it to 0 provides a safe
> default value and follows kernel coding best practices.
> 
> v2:
> - uval = 0 which serves as both a safe default and the fallback
>   value when the pcode read operation fails.
> 
> Fixes: 45832bf9c10f3 ("drm/xe/xe_late_bind_fw: Initialize late binding firmware")
> Signed-off-by: Mallesh Koujalagi <mallesh.koujalagi@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_late_bind_fw.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_late_bind_fw.c b/drivers/gpu/drm/xe/xe_late_bind_fw.c
> index 38f3feb2aecd..46981a6f28ae 100644
> --- a/drivers/gpu/drm/xe/xe_late_bind_fw.c
> +++ b/drivers/gpu/drm/xe/xe_late_bind_fw.c
> @@ -188,13 +188,11 @@ static int xe_late_bind_fw_num_fans(struct xe_late_bind *late_bind)
>  {
>  	struct xe_device *xe = late_bind_to_xe(late_bind);
>  	struct xe_tile *root_tile = xe_device_get_root_tile(xe);
> -	u32 uval;
> +	u32 uval = 0;
>  
> -	if (!xe_pcode_read(root_tile,
> -			   PCODE_MBOX(FAN_SPEED_CONTROL, FSC_READ_NUM_FANS, 0), &uval, NULL))
> -		return uval;
> -	else
> -		return 0;
> +	xe_pcode_read(root_tile,
> +		      PCODE_MBOX(FAN_SPEED_CONTROL, FSC_READ_NUM_FANS, 0), &uval, NULL);
> +	return uval;

I'm afraid both code are wrong.

Although this version is cleaner and not returning garbage, you are still
returning 0 when MMIO operation failed. That propagates 0 and success upwards.

This function should probably return the error and make the uval as pointer-argument,
like the pcode_read.

Then also change the caller of this function to propagate the error upwards
if mmio failed.

>  }
>  
>  void xe_late_bind_wait_for_worker_completion(struct xe_late_bind *late_bind)
> -- 
> 2.34.1
>