[PATCH 3/3] drm/dp: Add a drm_aux-dev module for reading/writing dpcd registers.

Rafael Antognolli rafael.antognolli at intel.com
Mon Sep 14 16:12:32 PDT 2015


This module is heavily based on i2c-dev. Once loaded, it provides one
dev node per DP AUX channel, named drm_aux-N.

It's possible to know which connector owns this aux channel by looking
at the respective sysfs /sys/class/drm_aux-dev/drm_aux-N/connector, if
the connector device pointer was correctly set in the aux helper struct.

Two main operations are provided on the registers through ioctls: read
and write; and a helper struct is provided for that, used as:

	- address is the address of the register to read/write;
	- len is the number of bytes to read/write;
	- buf is a pointer to a buffer where to store the read data, or
	  where the data to be written is already stored;
	- the return value is the number of bytes read/written, on
	  success, or the error code otherwise. The number of
	  read/written bytes is also stored on the len field of the
	  struct.

Signed-off-by: Rafael Antognolli <rafael.antognolli at intel.com>
---
 Documentation/ioctl/ioctl-number.txt |   1 +
 drivers/gpu/drm/Kconfig              |   4 +
 drivers/gpu/drm/Makefile             |   1 +
 drivers/gpu/drm/drm_aux-dev.c        | 390 +++++++++++++++++++++++++++++++++++
 include/uapi/linux/Kbuild            |   1 +
 include/uapi/linux/drm_aux-dev.h     |  45 ++++
 6 files changed, 442 insertions(+)
 create mode 100644 drivers/gpu/drm/drm_aux-dev.c
 create mode 100644 include/uapi/linux/drm_aux-dev.h

diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt
index 611c522..ea76980 100644
--- a/Documentation/ioctl/ioctl-number.txt
+++ b/Documentation/ioctl/ioctl-number.txt
@@ -93,6 +93,7 @@ Code  Seq#(hex)	Include File		Comments
 ';'	64-7F	linux/vfio.h
 '@'	00-0F	linux/radeonfb.h	conflict!
 '@'	00-0F	drivers/video/aty/aty128fb.c	conflict!
+'@'	10-2F	drm_aux-dev
 'A'	00-1F	linux/apm_bios.h	conflict!
 'A'	00-0F	linux/agpgart.h		conflict!
 		and drivers/char/agp/compat_ioctl.h
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 1a0a8df..eae847c 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -25,6 +25,10 @@ config DRM_MIPI_DSI
 	bool
 	depends on DRM
 
+config DRM_AUX_CHARDEV
+	tristate "DRM DP AUX Interface"
+	depends on DRM
+
 config DRM_KMS_HELPER
 	tristate
 	depends on DRM
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 45e7719..a1a94306 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -32,6 +32,7 @@ CFLAGS_drm_trace_points.o := -I$(src)
 
 obj-$(CONFIG_DRM)	+= drm.o
 obj-$(CONFIG_DRM_MIPI_DSI) += drm_mipi_dsi.o
+obj-$(CONFIG_DRM_AUX_CHARDEV) += drm_aux-dev.o
 obj-$(CONFIG_DRM_TTM)	+= ttm/
 obj-$(CONFIG_DRM_TDFX)	+= tdfx/
 obj-$(CONFIG_DRM_R128)	+= r128/
diff --git a/drivers/gpu/drm/drm_aux-dev.c b/drivers/gpu/drm/drm_aux-dev.c
new file mode 100644
index 0000000..3ae9064
--- /dev/null
+++ b/drivers/gpu/drm/drm_aux-dev.c
@@ -0,0 +1,390 @@
+/*
+ * Copyright © 2015 Intel Corporation
+ *
+ * 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 AUTHORS OR COPYRIGHT HOLDERS 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.
+ *
+ * Authors:
+ *    Rafael Antognolli <rafael.antognolli at intel.com>
+ *
+ */
+
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/drm_aux-dev.h>
+#include <asm/uaccess.h>
+#include <drm/drm_dp_helper.h>
+#include <drm/drm_crtc.h>
+
+struct drm_aux_dev {
+	struct list_head list;
+	unsigned index;
+	struct drm_dp_aux *aux;
+	struct device *dev;
+};
+
+#define DRM_AUX_MINORS	256
+static int drm_aux_dev_count = 0;
+static LIST_HEAD(drm_aux_dev_list);
+static DEFINE_SPINLOCK(drm_aux_dev_list_lock);
+
+static struct drm_aux_dev *drm_aux_dev_get_by_minor(unsigned index)
+{
+	struct drm_aux_dev *aux_dev;
+
+	spin_lock(&drm_aux_dev_list_lock);
+	list_for_each_entry(aux_dev, &drm_aux_dev_list, list) {
+		if (aux_dev->index == index)
+			goto found;
+	}
+
+	aux_dev = NULL;
+found:
+	spin_unlock(&drm_aux_dev_list_lock);
+	return aux_dev;
+}
+
+static struct drm_aux_dev *drm_aux_dev_get_by_aux(struct drm_dp_aux *aux)
+{
+	struct drm_aux_dev *aux_dev;
+
+	spin_lock(&drm_aux_dev_list_lock);
+	list_for_each_entry(aux_dev, &drm_aux_dev_list, list) {
+		if (aux_dev->aux == aux)
+			goto found;
+	}
+
+	aux_dev = NULL;
+found:
+	spin_unlock(&drm_aux_dev_list_lock);
+	return aux_dev;
+}
+
+static struct drm_aux_dev *get_free_drm_aux_dev(struct drm_dp_aux *aux)
+{
+	struct drm_aux_dev *aux_dev;
+	int index;
+
+	spin_lock(&drm_aux_dev_list_lock);
+	index = drm_aux_dev_count;
+	spin_unlock(&drm_aux_dev_list_lock);
+	if (index >= DRM_AUX_MINORS) {
+		printk(KERN_ERR "i2c-dev: Out of device minors (%d)\n",
+		       index);
+		return ERR_PTR(-ENODEV);
+	}
+
+	aux_dev = kzalloc(sizeof(*aux_dev), GFP_KERNEL);
+	if (!aux_dev)
+		return ERR_PTR(-ENOMEM);
+	aux_dev->aux = aux;
+	aux_dev->index = index;
+
+	spin_lock(&drm_aux_dev_list_lock);
+	drm_aux_dev_count++;
+	list_add_tail(&aux_dev->list, &drm_aux_dev_list);
+	spin_unlock(&drm_aux_dev_list_lock);
+	return aux_dev;
+}
+
+static void return_drm_aux_dev(struct drm_aux_dev *aux_dev)
+{
+	spin_lock(&drm_aux_dev_list_lock);
+	list_del(&aux_dev->list);
+	spin_unlock(&drm_aux_dev_list_lock);
+	kfree(aux_dev);
+}
+
+static ssize_t name_show(struct device *dev,
+			 struct device_attribute *attr, char *buf)
+{
+	struct drm_aux_dev *aux_dev = drm_aux_dev_get_by_minor(MINOR(dev->devt));
+
+	if (!aux_dev)
+		return -ENODEV;
+	return sprintf(buf, "%s\n", aux_dev->aux->name);
+}
+static DEVICE_ATTR_RO(name);
+
+static ssize_t connector_show(struct device *dev,
+			      struct device_attribute *attr, char *buf)
+{
+	struct drm_aux_dev *aux_dev = drm_aux_dev_get_by_minor(MINOR(dev->devt));
+	struct drm_dp_aux *aux;
+	struct device *conn_dev;
+	struct drm_connector *connector = NULL;
+
+	if (!aux_dev)
+		return -ENODEV;
+	aux = aux_dev->aux;
+	conn_dev = aux->connector;
+	if (!conn_dev)
+		return sprintf(buf, "unknown\n");
+
+	connector = dev_get_drvdata(aux->connector);
+
+	return sprintf(buf, "%s\n", connector->name);
+}
+static DEVICE_ATTR_RO(connector);
+
+static struct attribute *drm_aux_attrs[] = {
+	&dev_attr_name.attr,
+	&dev_attr_connector.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(drm_aux);
+
+static long auxdev_ioctl_read(struct drm_aux_dev *aux_dev, unsigned long arg)
+{
+	struct drm_aux_dev_data rdwr_arg;
+	__u8 *buf;
+	int res;
+
+	/* Get register address, buffer and read length from user */
+	if (copy_from_user(&rdwr_arg,
+			   (struct drm_aux_dev_data __user *)arg,
+			   sizeof(rdwr_arg)))
+		return -EFAULT;
+
+	buf = memdup_user(rdwr_arg.buf, rdwr_arg.len * sizeof(__u8));
+	if (IS_ERR(buf))
+		return PTR_ERR(buf);
+
+	/* read register */
+	res = drm_dp_dpcd_read(aux_dev->aux, rdwr_arg.address, buf, rdwr_arg.len);
+	if (res < 0) {
+		kfree(buf);
+		return res;
+	}
+
+	/* return number of read bytes to user */
+	rdwr_arg.len = res;
+	if (copy_to_user((struct drm_aux_dev_data __user *)arg,
+			 &rdwr_arg, sizeof(rdwr_arg))) {
+		kfree(buf);
+		return -EFAULT;
+	}
+
+	/* return the read bytes to user */
+	if (copy_to_user((__u8 __user *)rdwr_arg.buf,
+			 buf, rdwr_arg.len)) {
+		kfree(buf);
+		return -EFAULT;
+	}
+
+	kfree(buf);
+	return res;
+}
+
+static long auxdev_ioctl_write(struct drm_aux_dev *aux_dev, unsigned long arg)
+{
+	struct drm_aux_dev_data rdwr_arg;
+	__u8 *buf;
+	int res;
+
+	/* Get register address and data to write */
+	if (copy_from_user(&rdwr_arg,
+			   (struct drm_aux_dev_data __user *)arg,
+			   sizeof(rdwr_arg)))
+		return -EFAULT;
+
+	buf = memdup_user(rdwr_arg.buf, rdwr_arg.len * sizeof(__u8));
+	if (IS_ERR(buf))
+		return PTR_ERR(buf);
+
+	/* write register */
+	res = drm_dp_dpcd_write(aux_dev->aux, rdwr_arg.address, buf, rdwr_arg.len);
+	if (res < 0) {
+		kfree(buf);
+		return res;
+	}
+
+	/* return length of written data */
+	rdwr_arg.len = res;
+	if (copy_to_user((struct drm_aux_dev_data __user *)arg,
+			 &rdwr_arg, sizeof(rdwr_arg))) {
+		kfree(buf);
+		return -EFAULT;
+	}
+
+	kfree(buf);
+	return res;
+}
+
+static long auxdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	struct drm_aux_dev *aux_dev = file->private_data;
+	dev_dbg(aux_dev->aux->dev, "ioctl, cmd=0x%02x, arg=0x%02lx\n",
+		cmd, arg);
+	switch (cmd) {
+	case DRM_AUX_DEV_READ:
+		return auxdev_ioctl_read(aux_dev, arg);
+	case DRM_AUX_DEV_WRITE:
+		return auxdev_ioctl_write(aux_dev, arg);
+	default:
+		return -ENOTTY;
+	}
+
+	return 0;
+}
+
+static int auxdev_open(struct inode *inode, struct file *file)
+{
+	unsigned int minor = iminor(inode);
+	struct drm_aux_dev *aux_dev;
+
+	aux_dev = drm_aux_dev_get_by_minor(minor);
+	if (!aux_dev)
+		return -ENODEV;
+
+	file->private_data = aux_dev;
+	return 0;
+}
+
+static const struct file_operations auxdev_fops = {
+	.owner		= THIS_MODULE,
+	.llseek		= no_llseek,
+	.unlocked_ioctl	= auxdev_ioctl,
+	.open		= auxdev_open,
+};
+
+static struct class *drm_aux_dev_class;
+static int drm_dev_major = -1;
+
+#define to_auxdev(d) container_of(d, struct drm_aux_dev, aux)
+
+static int auxdev_attach_aux(struct drm_dp_aux *aux, void *data)
+{
+	int *major = data;
+	struct drm_aux_dev *aux_dev;
+	int res;
+
+	aux_dev = get_free_drm_aux_dev(aux);
+	if (IS_ERR(aux_dev))
+		return PTR_ERR(aux_dev);
+
+	aux_dev->dev = device_create(drm_aux_dev_class, aux->dev,
+				     MKDEV(*major, aux_dev->index), NULL,
+				     "drm_aux-%d", aux_dev->index);
+	if (IS_ERR(aux_dev->dev)) {
+		res = PTR_ERR(aux_dev->dev);
+		goto error;
+	}
+
+	pr_debug("drm_aux-dev: aux [%s] registered as minor %d\n",
+		 aux->name, aux_dev->index);
+	return 0;
+error:
+	return_drm_aux_dev(aux_dev);
+	return res;
+
+}
+
+static int auxdev_detach_aux(struct drm_dp_aux *aux, void *data)
+{
+	int *major = data;
+	int minor;
+	struct drm_aux_dev *aux_dev;
+
+	aux_dev = drm_aux_dev_get_by_aux(aux);
+	if (!aux_dev) /* attach must have failed */
+		return 0;
+
+	minor = aux_dev->index;
+	return_drm_aux_dev(aux_dev);
+	device_destroy(drm_aux_dev_class, MKDEV(*major, minor));
+
+	pr_debug("drm_aux-dev: aux [%s] unregistered\n", aux->name);
+	return 0;
+}
+
+static int auxdev_notifier_call(struct notifier_block *nb, unsigned long action,
+				void *data)
+{
+	struct drm_dp_aux *aux = data;
+	switch (action) {
+	case DRM_DP_ADD_AUX:
+		return auxdev_attach_aux(aux, &drm_dev_major);
+	case DRM_DP_DEL_AUX:
+		return auxdev_detach_aux(aux, &drm_dev_major);
+	}
+
+	return 0;
+}
+
+static struct notifier_block auxdev_notifier = {
+	.notifier_call = auxdev_notifier_call,
+};
+
+static int __init drm_aux_dev_init(void)
+{
+	int res;
+
+	printk(KERN_INFO "drm dp aux /dev entries driver\n");
+
+	res = register_chrdev(0, "aux", &auxdev_fops);
+	if (res < 0)
+		goto out;
+	drm_dev_major = res;
+
+	drm_aux_dev_class = class_create(THIS_MODULE, "drm_aux-dev");
+	if (IS_ERR(drm_aux_dev_class)) {
+		res = PTR_ERR(drm_aux_dev_class);
+		goto out_unreg_chrdev;
+	}
+	drm_aux_dev_class->dev_groups = drm_aux_groups;
+
+	/* Keep track of DP aux that will be added or removed later */
+	res = drm_dp_aux_register_notifier(&auxdev_notifier);
+	if (res)
+		goto out_unreg_class;
+
+	/* Bind to already existing DP aux */
+	res = drm_dp_aux_for_each(&drm_dev_major, auxdev_attach_aux);
+
+	return 0;
+
+out_unreg_class:
+	class_destroy(drm_aux_dev_class);
+out_unreg_chrdev:
+	unregister_chrdev(drm_dev_major, "aux");
+out:
+	printk(KERN_ERR "%s: Driver Initialisation failed\n", __FILE__);
+	return res;
+}
+
+static void __exit drm_aux_dev_exit(void)
+{
+	printk(KERN_INFO "drm dp aux /dev entries driver - unloading\n");
+	drm_dp_aux_unregister_notifier(&auxdev_notifier);
+	drm_dp_aux_for_each(&drm_dev_major, auxdev_detach_aux);
+	class_destroy(drm_aux_dev_class);
+	unregister_chrdev(drm_dev_major, "aux");
+}
+
+MODULE_AUTHOR("Rafael Antognolli <rafael.antognolli at intel.com>");
+MODULE_DESCRIPTION("DRM DP AUX /dev entries driver");
+MODULE_LICENSE("GPL");
+
+module_init(drm_aux_dev_init);
+module_exit(drm_aux_dev_exit);
diff --git a/include/uapi/linux/Kbuild b/include/uapi/linux/Kbuild
index 1ff9942..07cdc8c 100644
--- a/include/uapi/linux/Kbuild
+++ b/include/uapi/linux/Kbuild
@@ -105,6 +105,7 @@ header-y += dm-ioctl.h
 header-y += dm-log-userspace.h
 header-y += dn.h
 header-y += dqblk_xfs.h
+header-y += drm_aux-dev.h
 header-y += edd.h
 header-y += efs_fs_sb.h
 header-y += elfcore.h
diff --git a/include/uapi/linux/drm_aux-dev.h b/include/uapi/linux/drm_aux-dev.h
new file mode 100644
index 0000000..668b631
--- /dev/null
+++ b/include/uapi/linux/drm_aux-dev.h
@@ -0,0 +1,45 @@
+/*
+ * Copyright © 2015 Intel Corporation
+ *
+ * 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 AUTHORS OR COPYRIGHT HOLDERS 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.
+ *
+ * Authors:
+ *    Rafael Antognolli <rafael.antognolli at intel.com>
+ *
+ */
+
+#ifndef _UAPI_LINUX_DRM_AUX_DEV_H
+#define _UAPI_LINUX_DRM_AUX_DEV_H
+
+#include <linux/ioctl.h>
+#include <linux/types.h>
+
+#define DRM_AUX_DEV_MAGIC '@'
+
+struct drm_aux_dev_data {
+	__u32 address; /* of the register */
+	__u16 len; /* size of the read/write */
+	__u8 *buf;
+};
+
+#define DRM_AUX_DEV_READ _IOWR(DRM_AUX_DEV_MAGIC, 0x10, struct drm_aux_dev_data)
+#define DRM_AUX_DEV_WRITE _IOW(DRM_AUX_DEV_MAGIC, 0x11, struct drm_aux_dev_data)
+
+#endif // _UAPI_LINUX_DRM_AUX_DEV_H
-- 
2.4.0



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