'\" t
.\"     Title: struct drm_dp_aux
.\"    Author: 
.\" Generator: DocBook XSL Stylesheets v1.78.1 <http://docbook.sf.net/>
.\"      Date: May 2018
.\"    Manual: DRM Core
.\"    Source: Kernel Hackers Manual 3.16.56
.\"  Language: English
.\"
.TH "STRUCT DRM_DP_AUX" "9" "May 2018" "Kernel Hackers Manual 3\&.16\&" "DRM Core"
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.el       .ds Aq '
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.SH "NAME"
struct_drm_dp_aux \- DisplayPort AUX channel
.SH "SYNOPSIS"
.sp
.nf
struct drm_dp_aux {
  const char * name;
  struct i2c_adapter ddc;
  struct device * dev;
  struct mutex hw_mutex;
  ssize_t (* transfer) (struct drm_dp_aux *aux,struct drm_dp_aux_msg *msg);
};  
.fi
.SH "MEMBERS"
.PP
name
.RS 4
user\-visible name of this AUX channel and the I2C\-over\-AUX adapter
.RE
.PP
ddc
.RS 4
I2C adapter that can be used for I2C\-over\-AUX communication
.RE
.PP
dev
.RS 4
pointer to struct device that is the parent for this AUX channel
.RE
.PP
hw_mutex
.RS 4
internal mutex used for locking transfers
.RE
.PP
transfer
.RS 4
transfers a message representing a single AUX transaction
.RE
.SH "DESCRIPTION"
.PP
The \&.dev field should be set to a pointer to the device that implements the AUX channel\&.
.PP
The \&.name field may be used to specify the name of the I2C adapter\&. If set to NULL,
\fBdev_name\fR
of \&.dev will be used\&.
.PP
Drivers provide a hardware\-specific implementation of how transactions are executed via the \&.\fBtransfer\fR
function\&. A pointer to a drm_dp_aux_msg structure describing the transaction is passed into this function\&. Upon success, the implementation should return the number of payload bytes that were transferred, or a negative error\-code on failure\&. Helpers propagate errors from the \&.\fBtransfer\fR
function, with the exception of the \-EBUSY error, which causes a transaction to be retried\&. On a short, helpers will return \-EPROTO to make it simpler to check for failure\&.
.PP
An AUX channel can also be used to transport I2C messages to a sink\&. A typical application of that is to access an EDID that\*(Aqs present in the sink device\&. The \&.\fBtransfer\fR
function can also be used to execute such transactions\&. The
\fBdrm_dp_aux_register_i2c_bus\fR
function registers an I2C adapter that can be passed to
\fBdrm_probe_ddc\fR\&. Upon removal, drivers should call
\fBdrm_dp_aux_unregister_i2c_bus\fR
to remove the I2C adapter\&.
.PP
Note that the aux helper code assumes that the \&.\fBtransfer\fR
function only modifies the reply field of the drm_dp_aux_msg structure\&. The retry logic and i2c helpers assume this is the case\&.
.SH "AUTHORS"
.PP
\fBJesse Barnes\fR <\&jesse.barnes@intel.com\&>
.br
Intel Corporation, 
	    
	  
.RS 4
Initial version
.RE
.PP
\fBLaurent Pinchart\fR <\&laurent.pinchart@ideasonboard.com\&>
.br
Ideas on board SPRL, 
	    
	  
.RS 4
Driver internals
.RE
.PP
\fBDaniel Vetter\fR <\&daniel.vetter@ffwll.ch\&>
.br
Intel Corporation, 
	    
	  
.RS 4
Contributions all over the place
.RE
.SH "COPYRIGHT"
.br