Re: [PATCH 05/13] drm/xe/guc: Add object KLV encoding helper

["Michał Winiarski" <michal.winiarski@intel.com>]

On Tue, Jun 30, 2026 at 03:26:24PM +0200, Michal Wajdeczko wrote:
> We plan to encode larger objects as single KLV or set of KLVs.
> Add helper for that.
> 
> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_guc_klv_helpers.c | 36 +++++++++++++++++++++++++
>  drivers/gpu/drm/xe/xe_guc_klv_helpers.h |  2 ++
>  2 files changed, 38 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_guc_klv_helpers.c b/drivers/gpu/drm/xe/xe_guc_klv_helpers.c
> index a5fcfc4a6c37..53a8beb9af04 100644
> --- a/drivers/gpu/drm/xe/xe_guc_klv_helpers.c
> +++ b/drivers/gpu/drm/xe/xe_guc_klv_helpers.c
> @@ -274,3 +274,39 @@ u32 *xe_guc_klv_encode_string(u32 *klvs, u32 avail, u16 key, const char *s)
>  	strscpy_pad((void *)klvs, s, to_num_bytes(len));
>  	return klvs + len;
>  }
> +
> +/**
> + * xe_guc_klv_encode_object() - Encode object using custom encoder as single KLV.
> + * @klvs: the buffer where to place KLV
> + * @avail: number of dwords (u32) available in the buffer
> + * @key: key to be used
> + * @obj: opaque object pointer
> + * @encoder: function pointer to the custom encoder
> + *
> + * Return: pointer to the buffer location past the encoded KLV or
> + *         an ERR_PTR if there was no space to encode the KLV.
> + */
> +u32 *xe_guc_klv_encode_object(u32 *klvs, u32 avail, u16 key, const void *obj,
> +			      u32 *(*encoder)(u32 *klvs, u32 avail, const void *obj))
> +{
> +	u32 *end;
> +
> +	if (IS_ERR(klvs))
> +		return klvs;
> +
> +	if (avail < GUC_KLV_LEN_MIN)
> +		return ERR_PTR(-ENOSPC);
> +
> +	end = encoder(klvs + GUC_KLV_LEN_MIN, avail - GUC_KLV_LEN_MIN, obj);
> +	if (IS_ERR(end))
> +		return end;

Similar to string helper - we might want to error out if the object
would get truncated (also spotted by sashiko).

Thanks,
-Michał

> +
> +	if (WARN_ON(end < klvs + GUC_KLV_LEN_MIN))
> +		return ERR_PTR(-EPIPE);
> +
> +	if (WARN_ON(end > klvs + avail))
> +		return ERR_PTR(-EFBIG);
> +
> +	*klvs = PREP_GUC_KLV(key, end - (klvs + GUC_KLV_LEN_MIN));
> +	return end;
> +}
> diff --git a/drivers/gpu/drm/xe/xe_guc_klv_helpers.h b/drivers/gpu/drm/xe/xe_guc_klv_helpers.h
> index 1c576456efc5..855805f4463d 100644
> --- a/drivers/gpu/drm/xe/xe_guc_klv_helpers.h
> +++ b/drivers/gpu/drm/xe/xe_guc_klv_helpers.h
> @@ -20,6 +20,8 @@ int xe_guc_klv_count(const u32 *klvs, u32 num_dwords);
>  u32 *xe_guc_klv_encode_u32(u32 *klvs, u32 avail, u16 key, u32 value);
>  u32 *xe_guc_klv_encode_u64(u32 *klvs, u32 avail, u16 key, u64 value);
>  u32 *xe_guc_klv_encode_string(u32 *klvs, u32 avail, u16 key, const char *s);
> +u32 *xe_guc_klv_encode_object(u32 *klvs, u32 avail, u16 key, const void *obj,
> +			      u32 *(*encoder)(u32 *klvs, u32 avail, const void *obj));
>  
>  /**
>   * PREP_GUC_KLV - Prepare KLV header value based on provided key and len.
> -- 
> 2.47.1
>