drm_dp_dpcd_write_data(9)

✨ drm_dp_dpcd_write_data ✨

okay bestie so this is from the Kernel API Manual and it's giving "tiny function, big responsibilities" energy 💅 she writes a whole series of bytes to the DPCD and she does NOT do it casually.

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🌸 NAME 🌸

drm_dp_dpcd_write_data — write a series of bytes to the DPCD 🦋

like literally, a series of bytes, not just one, that's the whole point of her

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🎀 SYNOPSIS 🎀

int drm_dp_dpcd_write_data (struct drm_dp_aux *aux , unsigned int offset
, void *buffer , size_t size );

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💖 ARGUMENTS 💖

• aux — the DisplayPort AUX channel, and yes it can be SST or MST, both are welcome here 🫶
• offset — the address of the (first) register you're writing to, aka where the party starts
• buffer — the buffer holding the values you want to write, this is your payload bestie
• size — how many bytes are in buffer, don't lie to her about this 🌈

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👑 DESCRIPTION 👑

so here's the vibe check: she returns zero (0) on success 🎉, or a negative error code on failure, no cap.

• -EIO gets returned if the request was NAKed by the sink 😭 or if the retry count was exceeded (she tried, she really did)
• if not all bytes were transferred, this function returns -EPROTO — partial sends are not it fr fr
• errors coming from the underlying AUX channel transfer function get propagated to the caller, with one exception: -EBUSY, which just causes the transaction to be retried 🔁 (she's persistent like that)

ngl, keep an eye on those return codes — -EIO means the sink said no, -EPROTO means the bytes didn't all make it. both are real and both matter 💀

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🦋 SEE ALSO 🦋

okay this list is LONG but we're doing all of it, no skipping, periodt 💅

• Kernel file ./include/drm/display/drm_dp_helper.h
• struct drm_dp_vsc_sdp(9)
• struct drm_dp_as_sdp(9)
• drm_dp_dsc_sink_supports_format(9)
• drm_edp_backlight_supported(9)
• drm_dp_is_uhbr_rate(9)
• struct drm_dp_aux_msg(9)
• struct drm_dp_aux_cec(9)
• struct drm_dp_aux(9)
• drm_dp_dpcd_readb(9)
• drm_dp_dpcd_read_data(9)
• drm_dp_dpcd_writeb(9)
• drm_dp_dpcd_read_byte(9)
• drm_dp_dpcd_write_byte(9)
• struct drm_dp_desc(9)
• enum drm_dp_quirk(9)
• drm_dp_has_quirk(9)
• struct drm_edp_backlight_info(9)
• struct drm_dp_phy_test_params(9)

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and that's the whole page bestie, go write some bytes responsibly 💜

mwah 💋 this came from ./include/drm/display, dated October 2026 — that's the source and the date, and honestly? iconic of them to ship it like that ⭐