drm/kms: slave encoder interface.

Define some helper functions to make easier to detach a KMS encoder
implementation from the drm module of the GPU it's used in. This is
mainly useful for some external I2C encoders known to be present on
cards with GPUs from several different manufacturers.

Signed-off-by: Francisco Jerez <currojerez@riseup.net>
Signed-off-by: Dave Airlie <airlied@redhat.com>

2 files changed, 117 insertions, 1 deletions

diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index fe23f29f7cba..5f0aec4f082a 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -11,7 +11,7 @@ drm-y       :=	drm_auth.o drm_bufs.o drm_cache.o \
 		drm_agpsupport.o drm_scatter.o ati_pcigart.o drm_pci.o \
 		drm_sysfs.o drm_hashtab.o drm_sman.o drm_mm.o \
 		drm_crtc.o drm_crtc_helper.o drm_modes.o drm_edid.o \
-		drm_info.o drm_debugfs.o
+		drm_info.o drm_debugfs.o drm_encoder_slave.o
 
 drm-$(CONFIG_COMPAT) += drm_ioc32.o
 
diff --git a/drivers/gpu/drm/drm_encoder_slave.c b/drivers/gpu/drm/drm_encoder_slave.c
new file mode 100644
index 000000000000..6ffd600ccfae
--- /dev/null
+++ b/drivers/gpu/drm/drm_encoder_slave.c
@@ -0,0 +1,116 @@
+/*
+ * Copyright (C) 2009 Francisco Jerez.
+ * All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE COPYRIGHT OWNER(S) AND/OR ITS SUPPLIERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ */
+
+#include <drm/drm_encoder_slave.h>
+
+/**
+ * drm_i2c_encoder_init - Initialize an I2C slave encoder
+ * @dev:	DRM device.
+ * @encoder:    Encoder to be attached to the I2C device. You aren't
+ *		required to have called drm_encoder_init() before.
+ * @adap:	I2C adapter that will be used to communicate with
+ *		the device.
+ * @info:	Information that will be used to create the I2C device.
+ *		Required fields are @addr and @type.
+ *
+ * Create an I2C device on the specified bus (the module containing its
+ * driver is transparently loaded) and attach it to the specified
+ * &drm_encoder_slave. The @slave_funcs field will be initialized with
+ * the hooks provided by the slave driver.
+ *
+ * Returns 0 on success or a negative errno on failure, in particular,
+ * -ENODEV is returned when no matching driver is found.
+ */
+int drm_i2c_encoder_init(struct drm_device *dev,
+			 struct drm_encoder_slave *encoder,
+			 struct i2c_adapter *adap,
+			 const struct i2c_board_info *info)
+{
+	char modalias[sizeof(I2C_MODULE_PREFIX)
+		      + I2C_NAME_SIZE];
+	struct module *module = NULL;
+	struct i2c_client *client;
+	struct drm_i2c_encoder_driver *encoder_drv;
+	int err = 0;
+
+	snprintf(modalias, sizeof(modalias),
+		 "%s%s", I2C_MODULE_PREFIX, info->type);
+	request_module(modalias);
+
+	client = i2c_new_device(adap, info);
+	if (!client) {
+		err = -ENOMEM;
+		goto fail;
+	}
+
+	if (!client->driver) {
+		err = -ENODEV;
+		goto fail_unregister;
+	}
+
+	module = client->driver->driver.owner;
+	if (!try_module_get(module)) {
+		err = -ENODEV;
+		goto fail_unregister;
+	}
+
+	encoder->bus_priv = client;
+
+	encoder_drv = to_drm_i2c_encoder_driver(client->driver);
+
+	err = encoder_drv->encoder_init(client, dev, encoder);
+	if (err)
+		goto fail_unregister;
+
+	return 0;
+
+fail_unregister:
+	i2c_unregister_device(client);
+	module_put(module);
+fail:
+	return err;
+}
+EXPORT_SYMBOL(drm_i2c_encoder_init);
+
+/**
+ * drm_i2c_encoder_destroy - Unregister the I2C device backing an encoder
+ * @drm_encoder:	Encoder to be unregistered.
+ *
+ * This should be called from the @destroy method of an I2C slave
+ * encoder driver once I2C access is no longer needed.
+ */
+void drm_i2c_encoder_destroy(struct drm_encoder *drm_encoder)
+{
+	struct drm_encoder_slave *encoder = to_encoder_slave(drm_encoder);
+	struct i2c_client *client = drm_i2c_encoder_get_client(drm_encoder);
+	struct module *module = client->driver->driver.owner;
+
+	i2c_unregister_device(client);
+	encoder->bus_priv = NULL;
+
+	module_put(module);
+}
+EXPORT_SYMBOL(drm_i2c_encoder_destroy);