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drm/dp: add helper for reading DP sink/branch device desc from DPCD

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Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/acba54da7d80eafea9e59a893e27e3c31028c0ba.1495105635.git.jani.nikula@intel.com
This commit is contained in:
Jani Nikula
2017-05-18 14:10:22 +03:00
parent 5ed02dbb49
commit 118b90f3f1
2 changed files with 54 additions and 0 deletions
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35
drivers/gpu/drm/drm_dp_helper.c
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@@ -1208,3 +1208,38 @@ int drm_dp_stop_crc(struct drm_dp_aux *aux)
return 0;
}
EXPORT_SYMBOL(drm_dp_stop_crc);
/**
* drm_dp_read_desc - read sink/branch descriptor from DPCD
* @aux: DisplayPort AUX channel
* @desc: Device decriptor to fill from DPCD
* @is_branch: true for branch devices, false for sink devices
*
* Read DPCD 0x400 (sink) or 0x500 (branch) into @desc. Also debug log the
* identification.
*
* Returns 0 on success or a negative error code on failure.
*/
int drm_dp_read_desc(struct drm_dp_aux *aux, struct drm_dp_desc *desc,
bool is_branch)
{
struct drm_dp_dpcd_ident *ident = &desc->ident;
unsigned int offset = is_branch ? DP_BRANCH_OUI : DP_SINK_OUI;
int ret, dev_id_len;
ret = drm_dp_dpcd_read(aux, offset, ident, sizeof(*ident));
if (ret < 0)
return ret;
dev_id_len = strnlen(ident->device_id, sizeof(ident->device_id));
DRM_DEBUG_KMS("DP %s: OUI %*phD dev-ID %*pE HW-rev %d.%d SW-rev %d.%d\n",
is_branch ? "branch" : "sink",
(int)sizeof(ident->oui), ident->oui,
dev_id_len, ident->device_id,
ident->hw_rev >> 4, ident->hw_rev & 0xf,
ident->sw_major_rev, ident->sw_minor_rev);
return 0;
}
EXPORT_SYMBOL(drm_dp_read_desc);