Re: [PATCH 04/13] drm/xe/guc: Add string KLV encoding helper

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

On Tue, Jun 30, 2026 at 03:26:23PM +0200, Michal Wajdeczko wrote:
> We also plan to encode a text data as KLV. Add helper for that too.
> 
> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_guc_klv_helpers.c | 31 +++++++++++++++++++++++++
>  drivers/gpu/drm/xe/xe_guc_klv_helpers.h |  1 +
>  2 files changed, 32 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_guc_klv_helpers.c b/drivers/gpu/drm/xe/xe_guc_klv_helpers.c
> index e84d1f5f5c56..a5fcfc4a6c37 100644
> --- a/drivers/gpu/drm/xe/xe_guc_klv_helpers.c
> +++ b/drivers/gpu/drm/xe/xe_guc_klv_helpers.c
> @@ -188,6 +188,11 @@ int xe_guc_klv_count(const u32 *klvs, u32 num_dwords)
>  	return num_dwords ? -ENODATA : num_klvs;
>  }
>  
> +static size_t to_num_bytes(u16 dwords)
> +{
> +	return dwords * sizeof(u32);
> +}
> +
>  static u16 to_num_dwords(size_t size)
>  {
>  	return round_up(size, sizeof(u32)) / sizeof(u32);
> @@ -243,3 +248,29 @@ u32 *xe_guc_klv_encode_u64(u32 *klvs, u32 avail, u16 key, u64 value)
>  	*klvs++ = upper_32_bits(value);
>  	return klvs;
>  }
> +
> +/**
> + * xe_guc_klv_encode_string() - Encode string as KLV.
> + * @klvs: the buffer where to place KLV
> + * @avail: number of dwords (u32) available in the buffer
> + * @key: key to be used
> + * @s: string to be encoded
> + *
> + * 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_string(u32 *klvs, u32 avail, u16 key, const char *s)
> +{
> +	size_t size = strnlen(s, FIELD_MAX(GUC_KLV_0_LEN) - 1) + 1; /* \0 */

We're mixing up units (dwords / bytes) here.
Also - should we error out if the string would get truncated?

Thanks,
-Michał

> +	u16 len = to_num_dwords(size);
> +
> +	if (IS_ERR(klvs))
> +		return klvs;
> +
> +	if (avail < GUC_KLV_LEN_MIN + len)
> +		return ERR_PTR(-ENOSPC);
> +
> +	*klvs++ = PREP_GUC_KLV(key, len);
> +	strscpy_pad((void *)klvs, s, to_num_bytes(len));
> +	return klvs + len;
> +}
> diff --git a/drivers/gpu/drm/xe/xe_guc_klv_helpers.h b/drivers/gpu/drm/xe/xe_guc_klv_helpers.h
> index 713ef7f7b9f2..1c576456efc5 100644
> --- a/drivers/gpu/drm/xe/xe_guc_klv_helpers.h
> +++ b/drivers/gpu/drm/xe/xe_guc_klv_helpers.h
> @@ -19,6 +19,7 @@ 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);
>  
>  /**
>   * PREP_GUC_KLV - Prepare KLV header value based on provided key and len.
> -- 
> 2.47.1
>