From 4cc4f09eaa06178bfa8a5b2c753cefb56e1048c8 Mon Sep 17 00:00:00 2001 From: Jani Nikula Date: Mon, 29 Mar 2021 16:37:16 +0300 Subject: drm/displayid: add separate drm_displayid.c MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit We'll be adding more DisplayID specific functions going forward, so start off by splitting out a few functions to a separate file. We don't bother with exporting the functions; at least for now they should be needed solely within drm.ko. No functional changes. Reviewed-by: Ville Syrjälä Signed-off-by: Jani Nikula Link: https://patchwork.freedesktop.org/patch/msgid/07942d5011891b8e8f77245c78b34f4af97a9315.1617024940.git.jani.nikula@intel.com --- drivers/gpu/drm/drm_displayid.c | 59 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 59 insertions(+) create mode 100644 drivers/gpu/drm/drm_displayid.c (limited to 'drivers/gpu/drm/drm_displayid.c') diff --git a/drivers/gpu/drm/drm_displayid.c b/drivers/gpu/drm/drm_displayid.c new file mode 100644 index 000000000000..908bbe6feb61 --- /dev/null +++ b/drivers/gpu/drm/drm_displayid.c @@ -0,0 +1,59 @@ +// SPDX-License-Identifier: MIT +/* + * Copyright © 2021 Intel Corporation + */ + +#include +#include +#include + +static int validate_displayid(const u8 *displayid, int length, int idx) +{ + int i, dispid_length; + u8 csum = 0; + const struct displayid_hdr *base; + + base = (const struct displayid_hdr *)&displayid[idx]; + + DRM_DEBUG_KMS("base revision 0x%x, length %d, %d %d\n", + base->rev, base->bytes, base->prod_id, base->ext_count); + + /* +1 for DispID checksum */ + dispid_length = sizeof(*base) + base->bytes + 1; + if (dispid_length > length - idx) + return -EINVAL; + + for (i = 0; i < dispid_length; i++) + csum += displayid[idx + i]; + if (csum) { + DRM_NOTE("DisplayID checksum invalid, remainder is %d\n", csum); + return -EINVAL; + } + + return 0; +} + +const u8 *drm_find_displayid_extension(const struct edid *edid, + int *length, int *idx, + int *ext_index) +{ + const u8 *displayid = drm_find_edid_extension(edid, DISPLAYID_EXT, ext_index); + const struct displayid_hdr *base; + int ret; + + if (!displayid) + return NULL; + + /* EDID extensions block checksum isn't for us */ + *length = EDID_LENGTH - 1; + *idx = 1; + + ret = validate_displayid(displayid, *length, *idx); + if (ret) + return NULL; + + base = (const struct displayid_hdr *)&displayid[*idx]; + *length = *idx + sizeof(*base) + base->bytes; + + return displayid; +} -- cgit v1.2.3