drm: use mem_is_zero() instead of !memchr_inv(s, 0, n)

Use the mem_is_zero() helper where possible.

Conversion done using cocci:

| @@
| expression PTR;
| expression SIZE;
| @@
|
|   <...
| (
| - memchr_inv(PTR, 0, SIZE) == NULL
| + mem_is_zero(PTR, SIZE)
| |
| - !memchr_inv(PTR, 0, SIZE)
| + mem_is_zero(PTR, SIZE)
| |
| - memchr_inv(PTR, 0, SIZE)
| + !mem_is_zero(PTR, SIZE)
| )
|   ...>
Reviewed-by: Kees Cook <kees@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240814100035.3100852-2-jani.nikula@intel.comSigned-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/drm_edid.c

@@ -1817,7 +1817,7 @@ static int edid_block_tag(const void *_block)
 
 static bool edid_block_is_zero(const void *edid)
 {
-	return !memchr_inv(edid, 0, EDID_LENGTH);
+	return mem_is_zero(edid, EDID_LENGTH);
 }
 
 static bool drm_edid_eq(const struct drm_edid *drm_edid,

drivers/gpu/drm/i915/display/intel_dp.c

@@ -5077,7 +5077,7 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp)
 			ack[3] |= DP_TUNNELING_IRQ;
 		}
 
-		if (!memchr_inv(ack, 0, sizeof(ack)))
+		if (mem_is_zero(ack, sizeof(ack)))
 			break;
 
 		if (!intel_dp_ack_sink_irq_esi(intel_dp, ack))

drivers/gpu/drm/i915/display/intel_opregion.c

@@ -1117,7 +1117,7 @@ const struct drm_edid *intel_opregion_get_edid(struct intel_connector *intel_con
 
 	/* Validity corresponds to number of 128-byte blocks */
 	len = (opregion->asle_ext->phed & ASLE_PHED_EDID_VALID_MASK) * 128;
-	if (!len || !memchr_inv(edid, 0, len))
+	if (!len || mem_is_zero(edid, len))
 		return NULL;
 
 	drm_edid = drm_edid_alloc(edid, len);

drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c

@@ -506,7 +506,7 @@ static int igt_dmabuf_export_vmap(void *arg)
 		goto out;
 	}
 
-	if (memchr_inv(ptr, 0, dmabuf->size)) {
+	if (!mem_is_zero(ptr, dmabuf->size)) {
 		pr_err("Exported object not initialised to zero!\n");
 		err = -EINVAL;
 		goto out;

drivers/gpu/drm/imagination/pvr_device.h

@@ -668,7 +668,7 @@ pvr_ioctl_union_padding_check(void *instance, size_t union_offset,
 	void *padding_start = ((u8 *)instance) + union_offset + member_size;
 	size_t padding_size = union_size - member_size;
 
-	return !memchr_inv(padding_start, 0, padding_size);
+	return mem_is_zero(padding_start, padding_size);
 }
 
 /**

drivers/gpu/drm/udl/udl_edid.c

@@ -69,7 +69,7 @@ bool udl_probe_edid(struct udl_device *udl)
 	 * The adapter sends all-zeros if no monitor has been
 	 * connected. We consider anything else a connection.
 	 */
-	return !!memchr_inv(hdr, 0, sizeof(hdr));
+	return !mem_is_zero(hdr, sizeof(hdr));
 }
 
 const struct drm_edid *udl_edid_read(struct drm_connector *connector)