This is a superset of the current i2c_dp_aux bus functionality and can
be used to transfer native AUX in addition to I2C-over-AUX messages.
Helpers are provided to read and write the DPCD, either blockwise or
byte-wise. Many of the existing helpers for DisplayPort take a copy of a
portion of the DPCD and operate on that, without a way to write data
back to the DPCD (e.g. for configuration of the link).
Subsequent patches will build upon this infrastructure to provide common
functionality in a generic way.
Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
---
drivers/gpu/drm/drm_dp_helper.c | 50 ++++++++++++++++++++++++
include/drm/drm_dp_helper.h | 85 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 135 insertions(+)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 9e978aae8972..6c9276098069 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -346,3 +346,53 @@ int drm_dp_bw_code_to_link_rate(u8 link_bw)
}
}
EXPORT_SYMBOL(drm_dp_bw_code_to_link_rate);
+
+/**
+ * drm_dp_dpcd_read() - read a series of bytes from the DPCD
+ * @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
+ *
+ * Returns the number of bytes transferred on success, or a negative error
+ * code on failure.
+ */
+ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
+ void *buffer, size_t size)
+{
+ struct drm_dp_aux_msg msg;
+
+ memset(&msg, 0, sizeof(msg));
+ msg.address = offset;
+ msg.flags = DRM_DP_AUX_NATIVE_READ;
+ msg.buffer = buffer;
+ msg.size = size;
+
+ return aux->transfer(aux, &msg);
+}
+EXPORT_SYMBOL(drm_dp_dpcd_read);
+
+/**
+ * drm_dp_dpcd_write() - write a series of bytes to the DPCD
+ * @aux: DisplayPort AUX channel
+ * @offset: address of the (first) register to write
+ * @buffer: buffer containing the values to write
+ * @size: number of bytes in @buffer
+ *
+ * Returns the number of bytes transferred on success, or a negative error
+ * code on failure.
+ */
+ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,
+ void *buffer, size_t size)
+{
+ struct drm_dp_aux_msg msg;
+
+ memset(&msg, 0, sizeof(msg));
+ msg.address = offset;
+ msg.flags = DRM_DP_AUX_NATIVE_WRITE;
+ msg.buffer = buffer;
+ msg.size = size;
+
+ return aux->transfer(aux, &msg);
+}
+EXPORT_SYMBOL(drm_dp_dpcd_write);
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index a92c3754e3bb..e528b2b64cef 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -397,4 +397,89 @@ drm_dp_enhanced_frame_cap(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
(dpcd[DP_MAX_LANE_COUNT] & DP_ENHANCED_FRAME_CAP);
}
+/*
+ * DisplayPort AUX channel
+ */
+
+/* A message is either a native AUX or I2C-over-AUX transaction */
+#define DRM_DP_AUX_MODE_MASK 0x1
+#define DRM_DP_AUX_NATIVE 0x0
+#define DRM_DP_AUX_I2C 0x1
+
+/*
+ * A message can be a read or write transaction. I2C messages can also be
+ * part of a larger transaction, in which case the MOT flag can be set.
+ */
+#define DRM_DP_AUX_WRITE (1 << 30)
+#define DRM_DP_AUX_I2C_MOT (1 << 31)
+
+#define DRM_DP_AUX_NATIVE_READ DRM_DP_AUX_NATIVE
+#define DRM_DP_AUX_NATIVE_WRITE (DRM_DP_AUX_WRITE | DRM_DP_AUX_NATIVE)
+
+#define DRM_DP_AUX_ACK (0 << 0)
+#define DRM_DP_AUX_NAK (1 << 0)
+#define DRM_DP_AUX_DEFER (2 << 0)
+#define DRM_DP_AUX_I2C_NAK (3 << 0)
+#define DRM_DP_AUX_I2C_DEFER (4 << 0)
+
+/**
+ * struct drm_dp_aux_msg - DisplayPort AUX channel transaction
+ * @address: address of the (first) register to access
+ * @flags: contains the type of transaction as well as flags (see above)
+ * @reply: upon completion, contains the reply type of the transaction
+ * @buffer: pointer to a transmission or reception buffer
+ * @size: size of @buffer
+ */
+struct drm_dp_aux_msg {
+ unsigned int address;
+ unsigned long flags;
+ unsigned long reply;
+ void *buffer;
+ size_t size;
+};
+
+/**
+ * struct drm_dp_aux - DisplayPort AUX channel
+ * @transfer: transfers a message representing a single AUX transaction
+ */
+struct drm_dp_aux {
+ ssize_t (*transfer)(struct drm_dp_aux *aux,
+ struct drm_dp_aux_msg *msg);
+};
+
+ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
+ void *buffer, size_t size);
+ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,
+ void *buffer, size_t size);
+
+/**
+ * drm_dp_dpcd_readb() - read a single byte from the DPCD
+ * @aux: DisplayPort AUX channel
+ * @offset: address of the register to read
+ * @valuep: location where the value of the register will be stored
+ *
+ * Returns the number of bytes transferred (1) on success, or a negative
+ * error code on failure.
+ */
+static inline ssize_t drm_dp_dpcd_readb(struct drm_dp_aux *aux,
+ unsigned int offset, u8 *valuep)
+{
+ return drm_dp_dpcd_read(aux, offset, valuep, 1);
+}
+
+/**
+ * drm_dp_dpcd_writeb() - write a single byte to the DPCD
+ * @aux: DisplayPort AUX channel
+ * @offset: address of the register to write
+ * @valuep: value to write to the register
+ *
+ * Returns the number of bytes transferred (1) on success, or a negative
+ * error code on failure.
+ */
+static inline ssize_t drm_dp_dpcd_writeb(struct drm_dp_aux *aux, u8 value,
+ unsigned int offset)
+{
+ return drm_dp_dpcd_write(aux, offset, &value, 1);
+}
+
#endif /* _DRM_DP_HELPER_H_ */
--
1.8.4.2
_______________________________________________
dri-devel mailing list
dri-devel@xxxxxxxxxxxxxxxxxxxxx
http://lists.freedesktop.org/mailman/listinfo/dri-devel
