[PATCH v2 04/13] drm/xe/guc: Add string KLV encoding helper

[Michal Wajdeczko <michal.wajdeczko@intel.com>]

We also plan to encode a text data as KLV. Add helper for that too.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
---
v2: don't mix units, report too long string (Michal/Sashiko)
---
 drivers/gpu/drm/xe/xe_guc_klv_helpers.c | 35 +++++++++++++++++++++++++
 drivers/gpu/drm/xe/xe_guc_klv_helpers.h |  1 +
 2 files changed, 36 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_guc_klv_helpers.c b/drivers/gpu/drm/xe/xe_guc_klv_helpers.c
index 5f94852a906f..45471738c150 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 +248,33 @@ 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 longest = to_num_bytes(FIELD_MAX(GUC_KLV_0_LEN));
+	size_t size = strnlen(s, longest) + 1; /* \0 */
+	u16 len = to_num_dwords(size);
+
+	if (IS_ERR(klvs))
+		return klvs;
+
+	if (size > longest)
+		return ERR_PTR(-E2BIG);
+
+	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