---
name: "drm_dp_dpcd_read"
section: "9"
platform: "linux"
package: "linux-manual-3.16"
version: "3.16.56-1+deb8u1"
release: "Debian 8 (Jessie)"
platforms: ["linux"]
url: "https://new.carta.tech/drm_dp_dpcd_read"
---

# drm\_dp\_dpcd\_read(9)

read a series of bytes from the DPCD

## NAME

drm\_dp\_dpcd\_read - read a series of bytes from the DPCD

## SYNOPSIS

**ssize\_t drm\_dp\_dpcd\_read(struct drm\_dp\_aux \*** *aux***, unsigned int** *offset***, void \*** *buffer***, size\_t** *size***);**

## ARGUMENTS

*aux*

DisplayPort AUX channel

*offset*

address of the (first) register to read

*buffer*

buffer to store the register values

*size*

number of bytes in *buffer*

## DESCRIPTION

Returns the number of bytes transferred on success, or a negative error code on failure. -EIO is returned if the request was NAKed by the sink or if the retry count was exceeded. If not all bytes were transferred, this function returns -EPROTO. Errors from the underlying AUX channel transfer function, with the exception of -EBUSY (which causes the transaction to be retried), are propagated to the caller.

## AUTHORS

**Jesse Barnes** \<jesse.barnes@intel.com\>\
 Intel Corporation,

Initial version

**Laurent Pinchart** \<laurent.pinchart@ideasonboard.com\>\
 Ideas on board SPRL,

Driver internals

**Daniel Vetter** \<daniel.vetter@ffwll.ch\>\
 Intel Corporation,

Contributions all over the place

## COPYRIGHT