Commit 1a24c364 authored by Jani Nikula's avatar Jani Nikula
Browse files

drm/displayid: add new displayid section/block iterators 



Iterating DisplayID blocks across sections (in EDID extensions) is
unnecessarily complicated for the caller. Implement DisplayID iterators
to go through all blocks in all sections.

Usage example:

	const struct displayid_block *block;
	struct displayid_iter iter;

	displayid_iter_edid_begin(edid, &iter);
	displayid_iter_for_each(block, &iter) {
		/* operate on block */
	}
	displayid_iter_end(&iter);

When DisplayID is stored in EDID extensions, the DisplayID sections map
to extensions as described in VESA DisplayID v1.3 Appendix B: DisplayID
as an EDID Extension. This is implemented here.

When DisplayID is stored in its dedicated DDC device 0xA4, according to
VESA E-DDC v1.3, different rules apply for the structure. This is not
implemented here, as we don't currently use it, but the idea is you'd
have a different call for beginning the iteration, for example simply:

	displayid_iter_begin(displayid, &iter);

instead of displayid_iter_edid_begin(), and everything else would be
hidden away in the iterator functions.

v2:
- sizeof(struct displayid_block) -> sizeof(*block) (Ville)
- remove __ prefix from displayid_iter_block

Reviewed-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: default avatarJani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/da3dead1752ab16c061f7bd248ac1a4268f7fefb.1617024940.git.jani.nikula@intel.com
parent 4cc4f09e

drivers/gpu/drm/drm_displayid.c

+74 −0
Original line number Diff line number Diff line
@@ -57,3 +57,77 @@ const u8 *drm_find_displayid_extension(const struct edid *edid, 


	return displayid;

}



void displayid_iter_edid_begin(const struct edid *edid,

			       struct displayid_iter *iter)

{

	memset(iter, 0, sizeof(*iter));



	iter->edid = edid;

}



static const struct displayid_block *

displayid_iter_block(const struct displayid_iter *iter)

{

	const struct displayid_block *block;



	if (!iter->section)

		return NULL;



	block = (const struct displayid_block *)&iter->section[iter->idx];



	if (iter->idx + sizeof(*block) <= iter->length &&

	    iter->idx + sizeof(*block) + block->num_bytes <= iter->length &&

	    block->num_bytes > 0)

		return block;



	return NULL;

}



const struct displayid_block *

__displayid_iter_next(struct displayid_iter *iter)

{

	const struct displayid_block *block;



	if (!iter->edid)

		return NULL;



	if (iter->section) {

		/* current block should always be valid */

		block = displayid_iter_block(iter);

		if (WARN_ON(!block)) {

			iter->section = NULL;

			iter->edid = NULL;

			return NULL;

		}



		/* next block in section */

		iter->idx += sizeof(*block) + block->num_bytes;



		block = displayid_iter_block(iter);

		if (block)

			return block;

	}



	for (;;) {

		iter->section = drm_find_displayid_extension(iter->edid,

							     &iter->length,

							     &iter->idx,

							     &iter->ext_index);

		if (!iter->section) {

			iter->edid = NULL;

			return NULL;

		}



		iter->idx += sizeof(struct displayid_hdr);



		block = displayid_iter_block(iter);

		if (block)

			return block;

	}

}



void displayid_iter_end(struct displayid_iter *iter)

{

	memset(iter, 0, sizeof(*iter));

}

include/drm/drm_displayid.h

+18 −0
Original line number Diff line number Diff line
@@ -108,4 +108,22 @@ const u8 *drm_find_displayid_extension(const struct edid *edid, 
				       int *length, int *idx,

				       int *ext_index);



/* DisplayID iteration */

struct displayid_iter {

	const struct edid *edid;



	const u8 *section;

	int length;

	int idx;

	int ext_index;

};



void displayid_iter_edid_begin(const struct edid *edid,

			       struct displayid_iter *iter);

const struct displayid_block *

__displayid_iter_next(struct displayid_iter *iter);

#define displayid_iter_for_each(__block, __iter) \

	while (((__block) = __displayid_iter_next(__iter)))

void displayid_iter_end(struct displayid_iter *iter);



#endif