STRUCT DRM_DP_AUX(9)

NAME
struct_drm_dp_aux - DisplayPort AUX channel

SYNOPSIS

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);
};

MEMBERS

name
    user-visible name of this AUX channel and the I2C-over-AUX adapter

ddc
    I2C adapter that can be used for I2C-over-AUX communication

dev
    pointer to struct device that is the parent for this AUX channel

hw_mutex
    internal mutex used for locking transfers

transfer
    transfers a message representing a single AUX transaction

DESCRIPTION

The .dev field should be set to a pointer to the device that implements the AUX channel.

The .name field may be used to specify the name of the I2C adapter. If set to NULL, dev_name of .dev will be used.

Drivers provide a hardware-specific implementation of how transactions are executed via the .transfer 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 .transfer 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.

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's present in the sink device. The .transfer function can also be used to execute such transactions. The drm_dp_aux_register_i2c_bus function registers an I2C adapter that can be passed to drm_probe_ddc. Upon removal, drivers should call drm_dp_aux_unregister_i2c_bus to remove the I2C adapter.

Note that the aux helper code assumes that the .transfer function only modifies the reply field of the drm_dp_aux_msg structure. The retry logic and i2c helpers assume this is the case.

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

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