Add some helpers to figure out the EDID extension block count, block
count, size, pointers to blocks.

Unfortunately, we'll need to cast away the const in a few places where
we actually need to access the data.

v2: fix s/j/i/ introduced in a rebase

Signed-off-by: Jani Nikula <jani.nik...@intel.com>
---
 drivers/gpu/drm/drm_edid.c | 80 +++++++++++++++++++++++++++-----------
 1 file changed, 57 insertions(+), 23 deletions(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 90615e30eaf5..c09ff1efdbc8 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -1568,6 +1568,38 @@ static const struct drm_display_mode edid_4k_modes[] = {
 
 /*** DDC fetch and block validation ***/
 
+static int edid_extension_block_count(const struct edid *edid)
+{
+       return edid->extensions;
+}
+
+static int edid_block_count(const struct edid *edid)
+{
+       return edid_extension_block_count(edid) + 1;
+}
+
+static int edid_size_by_blocks(int num_blocks)
+{
+       return num_blocks * EDID_LENGTH;
+}
+
+static int edid_size(const struct edid *edid)
+{
+       return edid_size_by_blocks(edid_block_count(edid));
+}
+
+static const void *edid_block_data(const struct edid *edid, int index)
+{
+       BUILD_BUG_ON(sizeof(*edid) != EDID_LENGTH);
+
+       return edid + index;
+}
+
+static const void *edid_extension_block_data(const struct edid *edid, int 
index)
+{
+       return edid_block_data(edid, index + 1);
+}
+
 static const u8 edid_header[] = {
        0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00
 };
@@ -1654,8 +1686,8 @@ bool drm_edid_are_equal(const struct edid *edid1, const 
struct edid *edid2)
                return false;
 
        if (edid1) {
-               edid1_len = EDID_LENGTH * (1 + edid1->extensions);
-               edid2_len = EDID_LENGTH * (1 + edid2->extensions);
+               edid1_len = edid_size(edid1);
+               edid2_len = edid_size(edid2);
 
                if (edid1_len != edid2_len)
                        return false;
@@ -1865,14 +1897,16 @@ EXPORT_SYMBOL(drm_edid_block_valid);
 bool drm_edid_is_valid(struct edid *edid)
 {
        int i;
-       u8 *raw = (u8 *)edid;
 
        if (!edid)
                return false;
 
-       for (i = 0; i <= edid->extensions; i++)
-               if (!drm_edid_block_valid(raw + i * EDID_LENGTH, i, true, NULL))
+       for (i = 0; i < edid_block_count(edid); i++) {
+               void *block = (void *)edid_block_data(edid, i);
+
+               if (!drm_edid_block_valid(block, i, true, NULL))
                        return false;
+       }
 
        return true;
 }
@@ -1885,13 +1919,13 @@ static struct edid *edid_filter_invalid_blocks(const 
struct edid *edid,
        int valid_extensions = edid->extensions - invalid_blocks;
        int i;
 
-       new = kmalloc_array(valid_extensions + 1, EDID_LENGTH, GFP_KERNEL);
+       new = kmalloc(edid_size_by_blocks(valid_extensions + 1), GFP_KERNEL);
        if (!new)
                goto out;
 
        dest_block = new;
-       for (i = 0; i <= edid->extensions; i++) {
-               const void *block = edid + i;
+       for (i = 0; i < edid_block_count(edid); i++) {
+               const void *block = edid_block_data(edid, i);
 
                if (edid_block_valid(block, i == 0))
                        memcpy(dest_block++, block, EDID_LENGTH);
@@ -2101,7 +2135,7 @@ struct edid *drm_do_get_edid(struct drm_connector 
*connector,
                             void *context)
 {
        enum edid_block_status status;
-       int j, invalid_blocks = 0;
+       int i, invalid_blocks = 0;
        struct edid *edid, *new;
 
        edid = drm_get_override_edid(connector);
@@ -2133,20 +2167,20 @@ struct edid *drm_do_get_edid(struct drm_connector 
*connector,
                goto fail;
        }
 
-       if (edid->extensions == 0)
+       if (!edid_extension_block_count(edid) == 0)
                goto ok;
 
-       new = krealloc(edid, (edid->extensions + 1) * EDID_LENGTH, GFP_KERNEL);
+       new = krealloc(edid, edid_size(edid), GFP_KERNEL);
        if (!new)
                goto fail;
        edid = new;
 
-       for (j = 1; j <= edid->extensions; j++) {
-               void *block = edid + j;
+       for (i = 1; i < edid_block_count(edid); i++) {
+               void *block = (void *)edid_block_data(edid, i);
 
-               status = edid_block_read(block, j, read_block, context);
+               status = edid_block_read(block, i, read_block, context);
 
-               edid_block_status_print(status, block, j);
+               edid_block_status_print(status, block, i);
 
                if (!edid_block_status_valid(status, edid_block_tag(block))) {
                        if (status == EDID_BLOCK_READ_FAIL)
@@ -2156,7 +2190,7 @@ struct edid *drm_do_get_edid(struct drm_connector 
*connector,
        }
 
        if (invalid_blocks) {
-               connector_bad_edid(connector, edid, edid->extensions + 1);
+               connector_bad_edid(connector, edid, edid_block_count(edid));
 
                edid = edid_filter_invalid_blocks(edid, invalid_blocks);
        }
@@ -2321,7 +2355,7 @@ EXPORT_SYMBOL(drm_get_edid_switcheroo);
  */
 struct edid *drm_edid_duplicate(const struct edid *edid)
 {
-       return kmemdup(edid, (edid->extensions + 1) * EDID_LENGTH, GFP_KERNEL);
+       return kmemdup(edid, edid_size(edid), GFP_KERNEL);
 }
 EXPORT_SYMBOL(drm_edid_duplicate);
 
@@ -2505,8 +2539,8 @@ drm_for_each_detailed_block(const struct edid *edid, 
detailed_cb *cb, void *clos
        for (i = 0; i < EDID_DETAILED_TIMINGS; i++)
                cb(&(edid->detailed_timings[i]), closure);
 
-       for (i = 1; i <= edid->extensions; i++) {
-               const u8 *ext = (const u8 *)edid + (i * EDID_LENGTH);
+       for (i = 0; i < edid_extension_block_count(edid); i++) {
+               const u8 *ext = edid_extension_block_data(edid, i);
 
                switch (*ext) {
                case CEA_EXT:
@@ -3476,17 +3510,17 @@ const u8 *drm_find_edid_extension(const struct edid 
*edid,
        int i;
 
        /* No EDID or EDID extensions */
-       if (edid == NULL || edid->extensions == 0)
+       if (!edid || !edid_extension_block_count(edid))
                return NULL;
 
        /* Find CEA extension */
-       for (i = *ext_index; i < edid->extensions; i++) {
-               edid_ext = (const u8 *)edid + EDID_LENGTH * (i + 1);
+       for (i = *ext_index; i < edid_extension_block_count(edid); i++) {
+               edid_ext = edid_extension_block_data(edid, i);
                if (edid_block_tag(edid_ext) == ext_id)
                        break;
        }
 
-       if (i >= edid->extensions)
+       if (i >= edid_extension_block_count(edid))
                return NULL;
 
        *ext_index = i + 1;
-- 
2.30.2

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