[PATCH v8 0/2] Add drm_dp_aux chardev support.

[PATCH v8 0/2] Add drm_dp_aux chardev support.

[Rafael Antognolli]

This series implement support to a drm_dp_aux chardev that allows reading and
writing an arbitrary amount of bytes to arbitrary dpcd register addresses using
regular read, write and lseek operations.

Rafael Antognolli (2):
  drm/dp: Add a drm_aux-dev module for reading/writing dpcd registers.
  drm/dp: Set aux.dev to the drm_connector device, instead of
    drm_device.

 drivers/gpu/drm/Kconfig          |   8 +
 drivers/gpu/drm/Makefile         |   1 +
 drivers/gpu/drm/drm_dp_aux_dev.c | 373 +++++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/drm_dp_helper.c  |  16 +-
 drivers/gpu/drm/i915/intel_dp.c  |  19 +-
 include/drm/drm_dp_aux_dev.h     |  50 ++++++
 6 files changed, 449 insertions(+), 18 deletions(-)
 create mode 100644 drivers/gpu/drm/drm_dp_aux_dev.c
 create mode 100644 include/drm/drm_dp_aux_dev.h

-- 
2.4.3

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[PATCH v8 1/2] drm/dp: Add a drm_aux-dev module for reading/writing dpcd registers.

[Rafael Antognolli]

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

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

Two main operations are provided on the registers read and write. The
address of the register to be read or written is given using lseek. The
seek position is updated upon read or write.

v2:
 - lseek is used to select the register to read/write
 - read/write are used instead of ioctl
 - no blocking_notifier is used, just a direct callback

v3:
 - use drm_dp_aux_dev prefix for public functions
 - chardev is named drm_dp_auxN
 - read/write don't allocate a buffer anymore, and transfer up to 16 bytes a
   time
 - remove notifier list from the implementation
 - option on menuconfig is now a boolean
 - add inline stub functions to avoid breakage when this option is disabled

v4:
 - fix build system changes - actually disable this module when not selected.

v5:
 - Use kref to avoid device closing while still in use
 - Don't use list, use an idr for storing aux_dev
 - Remove "connector" attribute
 - set aux.dev to the connector drm_connector device, instead of
   drm_device

v6:
 - Use atomic_t for usage count
 - Use a mutex instead of spinlock for idr lock
 - Destroy chardev immediately on unregister
 - other minor suggestions from Ville

v7:
 - style fixes
 - error handling fixes

v8:
 - more error handling fixes

Signed-off-by: Rafael Antognolli <rafael.antognolli@intel.com>
---
 drivers/gpu/drm/Kconfig          |   8 +
 drivers/gpu/drm/Makefile         |   1 +
 drivers/gpu/drm/drm_dp_aux_dev.c | 373 +++++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/drm_dp_helper.c  |  16 +-
 include/drm/drm_dp_aux_dev.h     |  50 ++++++
 5 files changed, 447 insertions(+), 1 deletion(-)
 create mode 100644 drivers/gpu/drm/drm_dp_aux_dev.c
 create mode 100644 include/drm/drm_dp_aux_dev.h

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index c4bf9a1..daefcce 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -25,6 +25,14 @@ config DRM_MIPI_DSI
 	bool
 	depends on DRM
 
+config DRM_DP_AUX_CHARDEV
+	bool "DRM DP AUX Interface"
+	depends on DRM
+	help
+	  Choose this option to enable a /dev/drm_dp_auxN node that allows to
+	  read and write values to arbitrary DPCD registers on the DP aux
+	  channel.
+
 config DRM_KMS_HELPER
 	tristate
 	depends on DRM
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 1e9ff4c..e48ec8f 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -28,6 +28,7 @@ drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o drm_probe_helper.o \
 drm_kms_helper-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
 drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o
 drm_kms_helper-$(CONFIG_DRM_KMS_CMA_HELPER) += drm_fb_cma_helper.o
+drm_kms_helper-$(CONFIG_DRM_DP_AUX_CHARDEV) += drm_dp_aux_dev.o
 
 obj-$(CONFIG_DRM_KMS_HELPER) += drm_kms_helper.o
 
diff --git a/drivers/gpu/drm/drm_dp_aux_dev.c b/drivers/gpu/drm/drm_dp_aux_dev.c
new file mode 100644
index 0000000..0269556
--- /dev/null
+++ b/drivers/gpu/drm/drm_dp_aux_dev.c
@@ -0,0 +1,373 @@
+/*
+ * 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@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/uaccess.h>
+#include <drm/drm_dp_helper.h>
+#include <drm/drm_crtc.h>
+#include <drm/drmP.h>
+
+struct drm_dp_aux_dev {
+	unsigned index;
+	struct drm_dp_aux *aux;
+	struct device *dev;
+	struct kref refcount;
+	atomic_t usecount;
+};
+
+#define DRM_AUX_MINORS	256
+#define AUX_MAX_OFFSET	(1 << 20)
+static DEFINE_IDR(aux_idr);
+static DEFINE_MUTEX(aux_idr_mutex);
+static struct class *drm_dp_aux_dev_class;
+static int drm_dev_major = -1;
+
+static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_minor(unsigned index)
+{
+	struct drm_dp_aux_dev *aux_dev = NULL;
+
+	mutex_lock(&aux_idr_mutex);
+	aux_dev = idr_find(&aux_idr, index);
+	if (!kref_get_unless_zero(&aux_dev->refcount))
+		aux_dev = NULL;
+	mutex_unlock(&aux_idr_mutex);
+
+	return aux_dev;
+}
+
+static struct drm_dp_aux_dev *alloc_drm_dp_aux_dev(struct drm_dp_aux *aux)
+{
+	struct drm_dp_aux_dev *aux_dev;
+	int index;
+
+	aux_dev = kzalloc(sizeof(*aux_dev), GFP_KERNEL);
+	if (!aux_dev)
+		return ERR_PTR(-ENOMEM);
+	aux_dev->aux = aux;
+	atomic_set(&aux_dev->usecount, 1);
+	kref_init(&aux_dev->refcount);
+
+	mutex_lock(&aux_idr_mutex);
+	index = idr_alloc_cyclic(&aux_idr, aux_dev, 0, DRM_AUX_MINORS,
+				 GFP_KERNEL);
+	mutex_unlock(&aux_idr_mutex);
+	if (index < 0) {
+		kfree(aux_dev);
+		return ERR_PTR(index);
+	}
+	aux_dev->index = index;
+
+	return aux_dev;
+}
+
+static void release_drm_dp_aux_dev(struct kref *ref)
+{
+	struct drm_dp_aux_dev *aux_dev =
+		container_of(ref, struct drm_dp_aux_dev, refcount);
+
+	kfree(aux_dev);
+}
+
+static ssize_t name_show(struct device *dev,
+			 struct device_attribute *attr, char *buf)
+{
+	ssize_t res;
+	struct drm_dp_aux_dev *aux_dev =
+		drm_dp_aux_dev_get_by_minor(MINOR(dev->devt));
+
+	if (!aux_dev)
+		return -ENODEV;
+
+	res = sprintf(buf, "%s\n", aux_dev->aux->name);
+	kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
+
+	return res;
+}
+static DEVICE_ATTR_RO(name);
+
+static struct attribute *drm_dp_aux_attrs[] = {
+	&dev_attr_name.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(drm_dp_aux);
+
+static int auxdev_open(struct inode *inode, struct file *file)
+{
+	unsigned int minor = iminor(inode);
+	struct drm_dp_aux_dev *aux_dev;
+
+	aux_dev = drm_dp_aux_dev_get_by_minor(minor);
+	if (!aux_dev)
+		return -ENODEV;
+
+	file->private_data = aux_dev;
+	return 0;
+}
+
+static loff_t auxdev_llseek(struct file *file, loff_t offset, int whence)
+{
+	return fixed_size_llseek(file, offset, whence, AUX_MAX_OFFSET);
+}
+
+static ssize_t auxdev_read(struct file *file, char __user *buf, size_t count,
+			   loff_t *offset)
+{
+	size_t bytes_pending, num_bytes_processed = 0;
+	struct drm_dp_aux_dev *aux_dev = file->private_data;
+	ssize_t res = 0;
+
+	if (!atomic_inc_not_zero(&aux_dev->usecount))
+		return -ENODEV;
+
+	bytes_pending = min((loff_t)count, AUX_MAX_OFFSET - (*offset));
+
+	if (!access_ok(VERIFY_WRITE, buf, bytes_pending)) {
+		res = -EFAULT;
+		goto out;
+	}
+
+	while (bytes_pending > 0) {
+		uint8_t localbuf[DP_AUX_MAX_PAYLOAD_BYTES];
+		ssize_t todo = min_t(size_t, bytes_pending, sizeof(localbuf));
+
+		res = drm_dp_dpcd_read(aux_dev->aux, *offset, localbuf, todo);
+		if (res <= 0) {
+			res = num_bytes_processed ? num_bytes_processed : res;
+			goto out;
+		}
+		if (__copy_to_user(buf + num_bytes_processed, localbuf, res)) {
+			res = num_bytes_processed ?
+				num_bytes_processed : -EFAULT;
+			goto out;
+		}
+		bytes_pending -= res;
+		*offset += res;
+		num_bytes_processed += res;
+		res = num_bytes_processed;
+	}
+
+out:
+	atomic_dec(&aux_dev->usecount);
+	wake_up_atomic_t(&aux_dev->usecount);
+	return res;
+}
+
+static ssize_t auxdev_write(struct file *file, const char __user *buf,
+			    size_t count, loff_t *offset)
+{
+	size_t bytes_pending, num_bytes_processed = 0;
+	struct drm_dp_aux_dev *aux_dev = file->private_data;
+	ssize_t res = 0;
+
+	if (!atomic_inc_not_zero(&aux_dev->usecount))
+		return -ENODEV;
+
+	bytes_pending = min((loff_t)count, AUX_MAX_OFFSET - *offset);
+
+	if (!access_ok(VERIFY_READ, buf, bytes_pending)) {
+		res = -EFAULT;
+		goto out;
+	}
+
+	while (bytes_pending > 0) {
+		uint8_t localbuf[DP_AUX_MAX_PAYLOAD_BYTES];
+		ssize_t todo = min_t(size_t, bytes_pending, sizeof(localbuf));
+
+		if (__copy_from_user(localbuf,
+				     buf + num_bytes_processed, todo)) {
+			res = num_bytes_processed ?
+				num_bytes_processed : -EFAULT;
+			goto out;
+		}
+
+		res = drm_dp_dpcd_write(aux_dev->aux, *offset, localbuf, todo);
+		if (res <= 0) {
+			res = num_bytes_processed ? num_bytes_processed : res;
+			goto out;
+		}
+		bytes_pending -= res;
+		*offset += res;
+		num_bytes_processed += res;
+		res = num_bytes_processed;
+	}
+
+out:
+	atomic_dec(&aux_dev->usecount);
+	wake_up_atomic_t(&aux_dev->usecount);
+	return res;
+}
+
+static int auxdev_release(struct inode *inode, struct file *file)
+{
+	struct drm_dp_aux_dev *aux_dev = file->private_data;
+
+	kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
+	return 0;
+}
+
+static const struct file_operations auxdev_fops = {
+	.owner		= THIS_MODULE,
+	.llseek		= auxdev_llseek,
+	.read		= auxdev_read,
+	.write		= auxdev_write,
+	.open		= auxdev_open,
+	.release	= auxdev_release,
+};
+
+#define to_auxdev(d) container_of(d, struct drm_dp_aux_dev, aux)
+
+static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_aux(struct drm_dp_aux *aux)
+{
+	struct drm_dp_aux_dev *iter, *aux_dev = NULL;
+	int id;
+
+	/* don't increase kref count here because this function should only be
+	 * used by drm_dp_aux_unregister_devnode. Thus, it will always have at
+	 * least one reference - the one that drm_dp_aux_register_devnode
+	 * created
+	 */
+	mutex_lock(&aux_idr_mutex);
+	idr_for_each_entry(&aux_idr, iter, id) {
+		if (iter->aux == aux) {
+			aux_dev = iter;
+			break;
+		}
+	}
+	mutex_unlock(&aux_idr_mutex);
+	return aux_dev;
+}
+
+static int auxdev_wait_atomic_t(atomic_t *p)
+{
+	schedule();
+	return 0;
+}
+/**
+ * drm_dp_aux_unregister_devnode() - unregister a devnode for this aux channel
+ * @aux: DisplayPort AUX channel
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+void drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux)
+{
+	struct drm_dp_aux_dev *aux_dev;
+	unsigned int minor;
+
+	aux_dev = drm_dp_aux_dev_get_by_aux(aux);
+	if (!aux_dev) /* attach must have failed */
+		return;
+
+	mutex_lock(&aux_idr_mutex);
+	idr_remove(&aux_idr, aux_dev->index);
+	mutex_unlock(&aux_idr_mutex);
+
+	atomic_dec(&aux_dev->usecount);
+	wait_on_atomic_t(&aux_dev->usecount, auxdev_wait_atomic_t,
+			 TASK_UNINTERRUPTIBLE);
+
+	minor = aux_dev->index;
+	if (aux_dev->dev)
+		device_destroy(drm_dp_aux_dev_class,
+			       MKDEV(drm_dev_major, minor));
+
+	DRM_DEBUG("drm_dp_aux_dev: aux [%s] unregistering\n", aux->name);
+	kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
+}
+EXPORT_SYMBOL(drm_dp_aux_unregister_devnode);
+
+/**
+ * drm_dp_aux_register_devnode() - register a devnode for this aux channel
+ * @aux: DisplayPort AUX channel
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+int drm_dp_aux_register_devnode(struct drm_dp_aux *aux)
+{
+	struct drm_dp_aux_dev *aux_dev;
+	int res;
+
+	aux_dev = alloc_drm_dp_aux_dev(aux);
+	if (IS_ERR(aux_dev))
+		return PTR_ERR(aux_dev);
+
+	aux_dev->dev = device_create(drm_dp_aux_dev_class, aux->dev,
+				     MKDEV(drm_dev_major, aux_dev->index), NULL,
+				     "drm_dp_aux%d", aux_dev->index);
+	if (IS_ERR(aux_dev->dev)) {
+		res = PTR_ERR(aux_dev->dev);
+		aux_dev->dev = NULL;
+		goto error;
+	}
+
+	DRM_DEBUG("drm_dp_aux_dev: aux [%s] registered as minor %d\n",
+		  aux->name, aux_dev->index);
+	return 0;
+error:
+	drm_dp_aux_unregister_devnode(aux);
+	return res;
+}
+EXPORT_SYMBOL(drm_dp_aux_register_devnode);
+
+static int __init drm_dp_aux_dev_init(void)
+{
+	int res;
+
+	drm_dp_aux_dev_class = class_create(THIS_MODULE, "drm_dp_aux_dev");
+	if (IS_ERR(drm_dp_aux_dev_class)) {
+		res = PTR_ERR(drm_dp_aux_dev_class);
+		goto out;
+	}
+	drm_dp_aux_dev_class->dev_groups = drm_dp_aux_groups;
+
+	res = register_chrdev(0, "aux", &auxdev_fops);
+	if (res < 0)
+		goto out;
+	drm_dev_major = res;
+
+	return 0;
+out:
+	class_destroy(drm_dp_aux_dev_class);
+	return res;
+}
+
+static void __exit drm_dp_aux_dev_exit(void)
+{
+	unregister_chrdev(drm_dev_major, "aux");
+	class_destroy(drm_dp_aux_dev_class);
+}
+
+MODULE_AUTHOR("Rafael Antognolli <rafael.antognolli@intel.com>");
+MODULE_DESCRIPTION("DRM DP AUX /dev entries driver");
+MODULE_LICENSE("GPL and additional rights");
+
+module_init(drm_dp_aux_dev_init);
+module_exit(drm_dp_aux_dev_exit);
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 9535c5b..7d58f59 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -28,6 +28,7 @@
 #include <linux/sched.h>
 #include <linux/i2c.h>
 #include <drm/drm_dp_helper.h>
+#include <drm/drm_dp_aux_dev.h>
 #include <drm/drmP.h>
 
 /**
@@ -754,6 +755,8 @@ static const struct i2c_algorithm drm_dp_i2c_algo = {
  */
 int drm_dp_aux_register(struct drm_dp_aux *aux)
 {
+	int ret;
+
 	mutex_init(&aux->hw_mutex);
 
 	aux->ddc.algo = &drm_dp_i2c_algo;
@@ -768,7 +771,17 @@ int drm_dp_aux_register(struct drm_dp_aux *aux)
 	strlcpy(aux->ddc.name, aux->name ? aux->name : dev_name(aux->dev),
 		sizeof(aux->ddc.name));
 
-	return i2c_add_adapter(&aux->ddc);
+	ret = drm_dp_aux_register_devnode(aux);
+	if (ret)
+		return ret;
+
+	ret = i2c_add_adapter(&aux->ddc);
+	if (ret) {
+		drm_dp_aux_unregister_devnode(aux);
+		return ret;
+	}
+
+	return 0;
 }
 EXPORT_SYMBOL(drm_dp_aux_register);
 
@@ -778,6 +791,7 @@ EXPORT_SYMBOL(drm_dp_aux_register);
  */
 void drm_dp_aux_unregister(struct drm_dp_aux *aux)
 {
+	drm_dp_aux_unregister_devnode(aux);
 	i2c_del_adapter(&aux->ddc);
 }
 EXPORT_SYMBOL(drm_dp_aux_unregister);
diff --git a/include/drm/drm_dp_aux_dev.h b/include/drm/drm_dp_aux_dev.h
new file mode 100644
index 0000000..391a2cf
--- /dev/null
+++ b/include/drm/drm_dp_aux_dev.h
@@ -0,0 +1,50 @@
+/*
+ * 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@intel.com>
+ *
+ */
+
+#ifndef DRM_DP_AUX_DEV
+#define DRM_DP_AUX_DEV
+
+#ifdef CONFIG_DRM_DP_AUX_CHARDEV
+
+int drm_dp_aux_register_devnode(struct drm_dp_aux *aux);
+void drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux);
+
+#else
+
+static inline int drm_dp_aux_register_devnode(struct drm_dp_aux *aux)
+{
+	return 0;
+}
+
+static inline void drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux)
+{
+	return 0;
+}
+
+#endif
+
+#endif
-- 
2.4.3

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Re: [PATCH v8 1/2] drm/dp: Add a drm_aux-dev module for reading/writing dpcd registers.

[Ville Syrjälä]

On Mon, Nov 02, 2015 at 12:33:47PM -0800, Rafael Antognolli wrote:
> This module is heavily based on i2c-dev. Once loaded, it provides one
> dev node per DP AUX channel, named drm_dp_auxN, where N is an integer.
> 
> It's possible to know which connector owns this aux channel by looking
> at the respective sysfs /sys/class/drm_aux_dev/drm_dp_auxN/connector, if
> the connector device pointer was correctly set in the aux helper struct.
> 
> Two main operations are provided on the registers read and write. The
> address of the register to be read or written is given using lseek. The
> seek position is updated upon read or write.
> 
> v2:
>  - lseek is used to select the register to read/write
>  - read/write are used instead of ioctl
>  - no blocking_notifier is used, just a direct callback
> 
> v3:
>  - use drm_dp_aux_dev prefix for public functions
>  - chardev is named drm_dp_auxN
>  - read/write don't allocate a buffer anymore, and transfer up to 16 bytes a
>    time
>  - remove notifier list from the implementation
>  - option on menuconfig is now a boolean
>  - add inline stub functions to avoid breakage when this option is disabled
> 
> v4:
>  - fix build system changes - actually disable this module when not selected.
> 
> v5:
>  - Use kref to avoid device closing while still in use
>  - Don't use list, use an idr for storing aux_dev
>  - Remove "connector" attribute
>  - set aux.dev to the connector drm_connector device, instead of
>    drm_device
> 
> v6:
>  - Use atomic_t for usage count
>  - Use a mutex instead of spinlock for idr lock
>  - Destroy chardev immediately on unregister
>  - other minor suggestions from Ville
> 
> v7:
>  - style fixes
>  - error handling fixes
> 
> v8:
>  - more error handling fixes
> 
> Signed-off-by: Rafael Antognolli <rafael.antognolli@intel.com>

I thought I already r-b'd this. Let me do it again:
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> ---
>  drivers/gpu/drm/Kconfig          |   8 +
>  drivers/gpu/drm/Makefile         |   1 +
>  drivers/gpu/drm/drm_dp_aux_dev.c | 373 +++++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/drm_dp_helper.c  |  16 +-
>  include/drm/drm_dp_aux_dev.h     |  50 ++++++
>  5 files changed, 447 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/gpu/drm/drm_dp_aux_dev.c
>  create mode 100644 include/drm/drm_dp_aux_dev.h
> 
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index c4bf9a1..daefcce 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -25,6 +25,14 @@ config DRM_MIPI_DSI
>  	bool
>  	depends on DRM
>  
> +config DRM_DP_AUX_CHARDEV
> +	bool "DRM DP AUX Interface"
> +	depends on DRM
> +	help
> +	  Choose this option to enable a /dev/drm_dp_auxN node that allows to
> +	  read and write values to arbitrary DPCD registers on the DP aux
> +	  channel.
> +
>  config DRM_KMS_HELPER
>  	tristate
>  	depends on DRM
> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> index 1e9ff4c..e48ec8f 100644
> --- a/drivers/gpu/drm/Makefile
> +++ b/drivers/gpu/drm/Makefile
> @@ -28,6 +28,7 @@ drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o drm_probe_helper.o \
>  drm_kms_helper-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
>  drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o
>  drm_kms_helper-$(CONFIG_DRM_KMS_CMA_HELPER) += drm_fb_cma_helper.o
> +drm_kms_helper-$(CONFIG_DRM_DP_AUX_CHARDEV) += drm_dp_aux_dev.o
>  
>  obj-$(CONFIG_DRM_KMS_HELPER) += drm_kms_helper.o
>  
> diff --git a/drivers/gpu/drm/drm_dp_aux_dev.c b/drivers/gpu/drm/drm_dp_aux_dev.c
> new file mode 100644
> index 0000000..0269556
> --- /dev/null
> +++ b/drivers/gpu/drm/drm_dp_aux_dev.c
> @@ -0,0 +1,373 @@
> +/*
> + * 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@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/uaccess.h>
> +#include <drm/drm_dp_helper.h>
> +#include <drm/drm_crtc.h>
> +#include <drm/drmP.h>
> +
> +struct drm_dp_aux_dev {
> +	unsigned index;
> +	struct drm_dp_aux *aux;
> +	struct device *dev;
> +	struct kref refcount;
> +	atomic_t usecount;
> +};
> +
> +#define DRM_AUX_MINORS	256
> +#define AUX_MAX_OFFSET	(1 << 20)
> +static DEFINE_IDR(aux_idr);
> +static DEFINE_MUTEX(aux_idr_mutex);
> +static struct class *drm_dp_aux_dev_class;
> +static int drm_dev_major = -1;
> +
> +static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_minor(unsigned index)
> +{
> +	struct drm_dp_aux_dev *aux_dev = NULL;
> +
> +	mutex_lock(&aux_idr_mutex);
> +	aux_dev = idr_find(&aux_idr, index);
> +	if (!kref_get_unless_zero(&aux_dev->refcount))
> +		aux_dev = NULL;
> +	mutex_unlock(&aux_idr_mutex);
> +
> +	return aux_dev;
> +}
> +
> +static struct drm_dp_aux_dev *alloc_drm_dp_aux_dev(struct drm_dp_aux *aux)
> +{
> +	struct drm_dp_aux_dev *aux_dev;
> +	int index;
> +
> +	aux_dev = kzalloc(sizeof(*aux_dev), GFP_KERNEL);
> +	if (!aux_dev)
> +		return ERR_PTR(-ENOMEM);
> +	aux_dev->aux = aux;
> +	atomic_set(&aux_dev->usecount, 1);
> +	kref_init(&aux_dev->refcount);
> +
> +	mutex_lock(&aux_idr_mutex);
> +	index = idr_alloc_cyclic(&aux_idr, aux_dev, 0, DRM_AUX_MINORS,
> +				 GFP_KERNEL);
> +	mutex_unlock(&aux_idr_mutex);
> +	if (index < 0) {
> +		kfree(aux_dev);
> +		return ERR_PTR(index);
> +	}
> +	aux_dev->index = index;
> +
> +	return aux_dev;
> +}
> +
> +static void release_drm_dp_aux_dev(struct kref *ref)
> +{
> +	struct drm_dp_aux_dev *aux_dev =
> +		container_of(ref, struct drm_dp_aux_dev, refcount);
> +
> +	kfree(aux_dev);
> +}
> +
> +static ssize_t name_show(struct device *dev,
> +			 struct device_attribute *attr, char *buf)
> +{
> +	ssize_t res;
> +	struct drm_dp_aux_dev *aux_dev =
> +		drm_dp_aux_dev_get_by_minor(MINOR(dev->devt));
> +
> +	if (!aux_dev)
> +		return -ENODEV;
> +
> +	res = sprintf(buf, "%s\n", aux_dev->aux->name);
> +	kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
> +
> +	return res;
> +}
> +static DEVICE_ATTR_RO(name);
> +
> +static struct attribute *drm_dp_aux_attrs[] = {
> +	&dev_attr_name.attr,
> +	NULL,
> +};
> +ATTRIBUTE_GROUPS(drm_dp_aux);
> +
> +static int auxdev_open(struct inode *inode, struct file *file)
> +{
> +	unsigned int minor = iminor(inode);
> +	struct drm_dp_aux_dev *aux_dev;
> +
> +	aux_dev = drm_dp_aux_dev_get_by_minor(minor);
> +	if (!aux_dev)
> +		return -ENODEV;
> +
> +	file->private_data = aux_dev;
> +	return 0;
> +}
> +
> +static loff_t auxdev_llseek(struct file *file, loff_t offset, int whence)
> +{
> +	return fixed_size_llseek(file, offset, whence, AUX_MAX_OFFSET);
> +}
> +
> +static ssize_t auxdev_read(struct file *file, char __user *buf, size_t count,
> +			   loff_t *offset)
> +{
> +	size_t bytes_pending, num_bytes_processed = 0;
> +	struct drm_dp_aux_dev *aux_dev = file->private_data;
> +	ssize_t res = 0;
> +
> +	if (!atomic_inc_not_zero(&aux_dev->usecount))
> +		return -ENODEV;
> +
> +	bytes_pending = min((loff_t)count, AUX_MAX_OFFSET - (*offset));
> +
> +	if (!access_ok(VERIFY_WRITE, buf, bytes_pending)) {
> +		res = -EFAULT;
> +		goto out;
> +	}
> +
> +	while (bytes_pending > 0) {
> +		uint8_t localbuf[DP_AUX_MAX_PAYLOAD_BYTES];
> +		ssize_t todo = min_t(size_t, bytes_pending, sizeof(localbuf));
> +
> +		res = drm_dp_dpcd_read(aux_dev->aux, *offset, localbuf, todo);
> +		if (res <= 0) {
> +			res = num_bytes_processed ? num_bytes_processed : res;
> +			goto out;
> +		}
> +		if (__copy_to_user(buf + num_bytes_processed, localbuf, res)) {
> +			res = num_bytes_processed ?
> +				num_bytes_processed : -EFAULT;
> +			goto out;
> +		}
> +		bytes_pending -= res;
> +		*offset += res;
> +		num_bytes_processed += res;
> +		res = num_bytes_processed;
> +	}
> +
> +out:
> +	atomic_dec(&aux_dev->usecount);
> +	wake_up_atomic_t(&aux_dev->usecount);
> +	return res;
> +}
> +
> +static ssize_t auxdev_write(struct file *file, const char __user *buf,
> +			    size_t count, loff_t *offset)
> +{
> +	size_t bytes_pending, num_bytes_processed = 0;
> +	struct drm_dp_aux_dev *aux_dev = file->private_data;
> +	ssize_t res = 0;
> +
> +	if (!atomic_inc_not_zero(&aux_dev->usecount))
> +		return -ENODEV;
> +
> +	bytes_pending = min((loff_t)count, AUX_MAX_OFFSET - *offset);
> +
> +	if (!access_ok(VERIFY_READ, buf, bytes_pending)) {
> +		res = -EFAULT;
> +		goto out;
> +	}
> +
> +	while (bytes_pending > 0) {
> +		uint8_t localbuf[DP_AUX_MAX_PAYLOAD_BYTES];
> +		ssize_t todo = min_t(size_t, bytes_pending, sizeof(localbuf));
> +
> +		if (__copy_from_user(localbuf,
> +				     buf + num_bytes_processed, todo)) {
> +			res = num_bytes_processed ?
> +				num_bytes_processed : -EFAULT;
> +			goto out;
> +		}
> +
> +		res = drm_dp_dpcd_write(aux_dev->aux, *offset, localbuf, todo);
> +		if (res <= 0) {
> +			res = num_bytes_processed ? num_bytes_processed : res;
> +			goto out;
> +		}
> +		bytes_pending -= res;
> +		*offset += res;
> +		num_bytes_processed += res;
> +		res = num_bytes_processed;
> +	}
> +
> +out:
> +	atomic_dec(&aux_dev->usecount);
> +	wake_up_atomic_t(&aux_dev->usecount);
> +	return res;
> +}
> +
> +static int auxdev_release(struct inode *inode, struct file *file)
> +{
> +	struct drm_dp_aux_dev *aux_dev = file->private_data;
> +
> +	kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
> +	return 0;
> +}
> +
> +static const struct file_operations auxdev_fops = {
> +	.owner		= THIS_MODULE,
> +	.llseek		= auxdev_llseek,
> +	.read		= auxdev_read,
> +	.write		= auxdev_write,
> +	.open		= auxdev_open,
> +	.release	= auxdev_release,
> +};
> +
> +#define to_auxdev(d) container_of(d, struct drm_dp_aux_dev, aux)
> +
> +static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_aux(struct drm_dp_aux *aux)
> +{
> +	struct drm_dp_aux_dev *iter, *aux_dev = NULL;
> +	int id;
> +
> +	/* don't increase kref count here because this function should only be
> +	 * used by drm_dp_aux_unregister_devnode. Thus, it will always have at
> +	 * least one reference - the one that drm_dp_aux_register_devnode
> +	 * created
> +	 */
> +	mutex_lock(&aux_idr_mutex);
> +	idr_for_each_entry(&aux_idr, iter, id) {
> +		if (iter->aux == aux) {
> +			aux_dev = iter;
> +			break;
> +		}
> +	}
> +	mutex_unlock(&aux_idr_mutex);
> +	return aux_dev;
> +}
> +
> +static int auxdev_wait_atomic_t(atomic_t *p)
> +{
> +	schedule();
> +	return 0;
> +}
> +/**
> + * drm_dp_aux_unregister_devnode() - unregister a devnode for this aux channel
> + * @aux: DisplayPort AUX channel
> + *
> + * Returns 0 on success or a negative error code on failure.
> + */
> +void drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux)
> +{
> +	struct drm_dp_aux_dev *aux_dev;
> +	unsigned int minor;
> +
> +	aux_dev = drm_dp_aux_dev_get_by_aux(aux);
> +	if (!aux_dev) /* attach must have failed */
> +		return;
> +
> +	mutex_lock(&aux_idr_mutex);
> +	idr_remove(&aux_idr, aux_dev->index);
> +	mutex_unlock(&aux_idr_mutex);
> +
> +	atomic_dec(&aux_dev->usecount);
> +	wait_on_atomic_t(&aux_dev->usecount, auxdev_wait_atomic_t,
> +			 TASK_UNINTERRUPTIBLE);
> +
> +	minor = aux_dev->index;
> +	if (aux_dev->dev)
> +		device_destroy(drm_dp_aux_dev_class,
> +			       MKDEV(drm_dev_major, minor));
> +
> +	DRM_DEBUG("drm_dp_aux_dev: aux [%s] unregistering\n", aux->name);
> +	kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
> +}
> +EXPORT_SYMBOL(drm_dp_aux_unregister_devnode);
> +
> +/**
> + * drm_dp_aux_register_devnode() - register a devnode for this aux channel
> + * @aux: DisplayPort AUX channel
> + *
> + * Returns 0 on success or a negative error code on failure.
> + */
> +int drm_dp_aux_register_devnode(struct drm_dp_aux *aux)
> +{
> +	struct drm_dp_aux_dev *aux_dev;
> +	int res;
> +
> +	aux_dev = alloc_drm_dp_aux_dev(aux);
> +	if (IS_ERR(aux_dev))
> +		return PTR_ERR(aux_dev);
> +
> +	aux_dev->dev = device_create(drm_dp_aux_dev_class, aux->dev,
> +				     MKDEV(drm_dev_major, aux_dev->index), NULL,
> +				     "drm_dp_aux%d", aux_dev->index);
> +	if (IS_ERR(aux_dev->dev)) {
> +		res = PTR_ERR(aux_dev->dev);
> +		aux_dev->dev = NULL;
> +		goto error;
> +	}
> +
> +	DRM_DEBUG("drm_dp_aux_dev: aux [%s] registered as minor %d\n",
> +		  aux->name, aux_dev->index);
> +	return 0;
> +error:
> +	drm_dp_aux_unregister_devnode(aux);
> +	return res;
> +}
> +EXPORT_SYMBOL(drm_dp_aux_register_devnode);
> +
> +static int __init drm_dp_aux_dev_init(void)
> +{
> +	int res;
> +
> +	drm_dp_aux_dev_class = class_create(THIS_MODULE, "drm_dp_aux_dev");
> +	if (IS_ERR(drm_dp_aux_dev_class)) {
> +		res = PTR_ERR(drm_dp_aux_dev_class);
> +		goto out;
> +	}
> +	drm_dp_aux_dev_class->dev_groups = drm_dp_aux_groups;
> +
> +	res = register_chrdev(0, "aux", &auxdev_fops);
> +	if (res < 0)
> +		goto out;
> +	drm_dev_major = res;
> +
> +	return 0;
> +out:
> +	class_destroy(drm_dp_aux_dev_class);
> +	return res;
> +}
> +
> +static void __exit drm_dp_aux_dev_exit(void)
> +{
> +	unregister_chrdev(drm_dev_major, "aux");
> +	class_destroy(drm_dp_aux_dev_class);
> +}
> +
> +MODULE_AUTHOR("Rafael Antognolli <rafael.antognolli@intel.com>");
> +MODULE_DESCRIPTION("DRM DP AUX /dev entries driver");
> +MODULE_LICENSE("GPL and additional rights");
> +
> +module_init(drm_dp_aux_dev_init);
> +module_exit(drm_dp_aux_dev_exit);
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index 9535c5b..7d58f59 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -28,6 +28,7 @@
>  #include <linux/sched.h>
>  #include <linux/i2c.h>
>  #include <drm/drm_dp_helper.h>
> +#include <drm/drm_dp_aux_dev.h>
>  #include <drm/drmP.h>
>  
>  /**
> @@ -754,6 +755,8 @@ static const struct i2c_algorithm drm_dp_i2c_algo = {
>   */
>  int drm_dp_aux_register(struct drm_dp_aux *aux)
>  {
> +	int ret;
> +
>  	mutex_init(&aux->hw_mutex);
>  
>  	aux->ddc.algo = &drm_dp_i2c_algo;
> @@ -768,7 +771,17 @@ int drm_dp_aux_register(struct drm_dp_aux *aux)
>  	strlcpy(aux->ddc.name, aux->name ? aux->name : dev_name(aux->dev),
>  		sizeof(aux->ddc.name));
>  
> -	return i2c_add_adapter(&aux->ddc);
> +	ret = drm_dp_aux_register_devnode(aux);
> +	if (ret)
> +		return ret;
> +
> +	ret = i2c_add_adapter(&aux->ddc);
> +	if (ret) {
> +		drm_dp_aux_unregister_devnode(aux);
> +		return ret;
> +	}
> +
> +	return 0;
>  }
>  EXPORT_SYMBOL(drm_dp_aux_register);
>  
> @@ -778,6 +791,7 @@ EXPORT_SYMBOL(drm_dp_aux_register);
>   */
>  void drm_dp_aux_unregister(struct drm_dp_aux *aux)
>  {
> +	drm_dp_aux_unregister_devnode(aux);
>  	i2c_del_adapter(&aux->ddc);
>  }
>  EXPORT_SYMBOL(drm_dp_aux_unregister);
> diff --git a/include/drm/drm_dp_aux_dev.h b/include/drm/drm_dp_aux_dev.h
> new file mode 100644
> index 0000000..391a2cf
> --- /dev/null
> +++ b/include/drm/drm_dp_aux_dev.h
> @@ -0,0 +1,50 @@
> +/*
> + * 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@intel.com>
> + *
> + */
> +
> +#ifndef DRM_DP_AUX_DEV
> +#define DRM_DP_AUX_DEV
> +
> +#ifdef CONFIG_DRM_DP_AUX_CHARDEV
> +
> +int drm_dp_aux_register_devnode(struct drm_dp_aux *aux);
> +void drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux);
> +
> +#else
> +
> +static inline int drm_dp_aux_register_devnode(struct drm_dp_aux *aux)
> +{
> +	return 0;
> +}
> +
> +static inline void drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux)
> +{
> +	return 0;
> +}
> +
> +#endif
> +
> +#endif
> -- 
> 2.4.3
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Ville Syrjälä
Intel OTC
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/intel-gfx

Re: [Intel-gfx] [PATCH v8 1/2] drm/dp: Add a drm_aux-dev module for reading/writing dpcd registers.

[Ville Syrjälä]

On Mon, Nov 02, 2015 at 12:33:47PM -0800, Rafael Antognolli wrote:
<snip>
> +static int __init drm_dp_aux_dev_init(void)
> +{
> +	int res;
> +
> +	drm_dp_aux_dev_class = class_create(THIS_MODULE, "drm_dp_aux_dev");
> +	if (IS_ERR(drm_dp_aux_dev_class)) {
> +		res = PTR_ERR(drm_dp_aux_dev_class);
> +		goto out;
> +	}
> +	drm_dp_aux_dev_class->dev_groups = drm_dp_aux_groups;
> +
> +	res = register_chrdev(0, "aux", &auxdev_fops);
> +	if (res < 0)
> +		goto out;
> +	drm_dev_major = res;
> +
> +	return 0;
> +out:
> +	class_destroy(drm_dp_aux_dev_class);
> +	return res;
> +}
> +
> +static void __exit drm_dp_aux_dev_exit(void)
> +{
> +	unregister_chrdev(drm_dev_major, "aux");
> +	class_destroy(drm_dp_aux_dev_class);
> +}
> +
> +MODULE_AUTHOR("Rafael Antognolli <rafael.antognolli@intel.com>");
> +MODULE_DESCRIPTION("DRM DP AUX /dev entries driver");
> +MODULE_LICENSE("GPL and additional rights");
> +
> +module_init(drm_dp_aux_dev_init);
> +module_exit(drm_dp_aux_dev_exit);

Since this is no longer a separate module this stuff can cause a
build failure due to drm_fb_helper.c already providing a module_init
for the same module.

So maybe we neet to have module_init/exit for drm_kms_helper.o in
some central place and have those call the init/exit functions for
drm_fb_helper and drm_dp_aux_dev?

> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index 9535c5b..7d58f59 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -28,6 +28,7 @@
>  #include <linux/sched.h>
>  #include <linux/i2c.h>
>  #include <drm/drm_dp_helper.h>
> +#include <drm/drm_dp_aux_dev.h>
>  #include <drm/drmP.h>
>  
>  /**
> @@ -754,6 +755,8 @@ static const struct i2c_algorithm drm_dp_i2c_algo = {
>   */
>  int drm_dp_aux_register(struct drm_dp_aux *aux)
>  {
> +	int ret;
> +
>  	mutex_init(&aux->hw_mutex);
>  
>  	aux->ddc.algo = &drm_dp_i2c_algo;
> @@ -768,7 +771,17 @@ int drm_dp_aux_register(struct drm_dp_aux *aux)
>  	strlcpy(aux->ddc.name, aux->name ? aux->name : dev_name(aux->dev),
>  		sizeof(aux->ddc.name));
>  
> -	return i2c_add_adapter(&aux->ddc);
> +	ret = drm_dp_aux_register_devnode(aux);
> +	if (ret)
> +		return ret;
> +
> +	ret = i2c_add_adapter(&aux->ddc);
> +	if (ret) {
> +		drm_dp_aux_unregister_devnode(aux);
> +		return ret;
> +	}
> +
> +	return 0;
>  }
>  EXPORT_SYMBOL(drm_dp_aux_register);
>  
> @@ -778,6 +791,7 @@ EXPORT_SYMBOL(drm_dp_aux_register);
>   */
>  void drm_dp_aux_unregister(struct drm_dp_aux *aux)
>  {
> +	drm_dp_aux_unregister_devnode(aux);
>  	i2c_del_adapter(&aux->ddc);
>  }
>  EXPORT_SYMBOL(drm_dp_aux_unregister);
> diff --git a/include/drm/drm_dp_aux_dev.h b/include/drm/drm_dp_aux_dev.h
> new file mode 100644
> index 0000000..391a2cf
> --- /dev/null
> +++ b/include/drm/drm_dp_aux_dev.h
> @@ -0,0 +1,50 @@
> +/*
> + * 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@intel.com>
> + *
> + */
> +
> +#ifndef DRM_DP_AUX_DEV
> +#define DRM_DP_AUX_DEV
> +
> +#ifdef CONFIG_DRM_DP_AUX_CHARDEV
> +
> +int drm_dp_aux_register_devnode(struct drm_dp_aux *aux);
> +void drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux);
> +
> +#else
> +
> +static inline int drm_dp_aux_register_devnode(struct drm_dp_aux *aux)
> +{
> +	return 0;
> +}
> +
> +static inline void drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux)
> +{
> +	return 0;
> +}
> +
> +#endif
> +
> +#endif
> -- 
> 2.4.3
> 
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Ville Syrjälä
Intel OTC
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/dri-devel

[PATCH v8 2/2] drm/dp: Set aux.dev to the drm_connector device, instead of drm_device.

[Rafael Antognolli]

So far, the i915 driver and some other drivers set it to the drm_device,
which doesn't allow one to know which DP a given aux channel is related
to. Changing this to be the drm_connector provides proper nesting, still
allowing one to get the drm_device from it. Some drivers already set it
to the drm_connector.

This also removes the need to add a sysfs link for the i2c device under
the connector, as it will already be there.

Signed-off-by: Rafael Antognolli <rafael.antognolli@intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 19 ++-----------------
 1 file changed, 2 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 8287df4..7aacc08 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1078,36 +1078,21 @@ intel_dp_aux_init(struct intel_dp *intel_dp, struct intel_connector *connector)
 		intel_dp->aux_ch_ctl_reg = intel_dp->output_reg + 0x10;
 
 	intel_dp->aux.name = name;
-	intel_dp->aux.dev = dev->dev;
+	intel_dp->aux.dev = connector->base.kdev;
 	intel_dp->aux.transfer = intel_dp_aux_transfer;
 
 	DRM_DEBUG_KMS("registering %s bus for %s\n", name,
 		      connector->base.kdev->kobj.name);
 
 	ret = drm_dp_aux_register(&intel_dp->aux);
-	if (ret < 0) {
+	if (ret < 0)
 		DRM_ERROR("drm_dp_aux_register() for %s failed (%d)\n",
 			  name, ret);
-		return;
-	}
-
-	ret = sysfs_create_link(&connector->base.kdev->kobj,
-				&intel_dp->aux.ddc.dev.kobj,
-				intel_dp->aux.ddc.dev.kobj.name);
-	if (ret < 0) {
-		DRM_ERROR("sysfs_create_link() for %s failed (%d)\n", name, ret);
-		drm_dp_aux_unregister(&intel_dp->aux);
-	}
 }
 
 static void
 intel_dp_connector_unregister(struct intel_connector *intel_connector)
 {
-	struct intel_dp *intel_dp = intel_attached_dp(&intel_connector->base);
-
-	if (!intel_connector->mst_port)
-		sysfs_remove_link(&intel_connector->base.kdev->kobj,
-				  intel_dp->aux.ddc.dev.kobj.name);
 	intel_connector_unregister(intel_connector);
 }
 
-- 
2.4.3

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Re: [PATCH v8 2/2] drm/dp: Set aux.dev to the drm_connector device, instead of drm_device.

[Ville Syrjälä]

On Mon, Nov 02, 2015 at 12:33:48PM -0800, Rafael Antognolli wrote:
> So far, the i915 driver and some other drivers set it to the drm_device,
> which doesn't allow one to know which DP a given aux channel is related
> to. Changing this to be the drm_connector provides proper nesting, still
> allowing one to get the drm_device from it. Some drivers already set it
> to the drm_connector.
> 
> This also removes the need to add a sysfs link for the i2c device under
> the connector, as it will already be there.
> 
> Signed-off-by: Rafael Antognolli <rafael.antognolli@intel.com>

I gave aux_dev a bit of a testing here, and it appaers to work quite
splendidly.

This patch however causes lots of WARN spew if I unload the driver
while in middle of dumping the DPCD via the aux_dev. It appears we
we clean up things the wrong order now.

> ---
>  drivers/gpu/drm/i915/intel_dp.c | 19 ++-----------------
>  1 file changed, 2 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 8287df4..7aacc08 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -1078,36 +1078,21 @@ intel_dp_aux_init(struct intel_dp *intel_dp, struct intel_connector *connector)
>  		intel_dp->aux_ch_ctl_reg = intel_dp->output_reg + 0x10;
>  
>  	intel_dp->aux.name = name;
> -	intel_dp->aux.dev = dev->dev;
> +	intel_dp->aux.dev = connector->base.kdev;
>  	intel_dp->aux.transfer = intel_dp_aux_transfer;
>  
>  	DRM_DEBUG_KMS("registering %s bus for %s\n", name,
>  		      connector->base.kdev->kobj.name);
>  
>  	ret = drm_dp_aux_register(&intel_dp->aux);
> -	if (ret < 0) {
> +	if (ret < 0)
>  		DRM_ERROR("drm_dp_aux_register() for %s failed (%d)\n",
>  			  name, ret);
> -		return;
> -	}
> -
> -	ret = sysfs_create_link(&connector->base.kdev->kobj,
> -				&intel_dp->aux.ddc.dev.kobj,
> -				intel_dp->aux.ddc.dev.kobj.name);
> -	if (ret < 0) {
> -		DRM_ERROR("sysfs_create_link() for %s failed (%d)\n", name, ret);
> -		drm_dp_aux_unregister(&intel_dp->aux);
> -	}
>  }
>  
>  static void
>  intel_dp_connector_unregister(struct intel_connector *intel_connector)
>  {
> -	struct intel_dp *intel_dp = intel_attached_dp(&intel_connector->base);
> -
> -	if (!intel_connector->mst_port)
> -		sysfs_remove_link(&intel_connector->base.kdev->kobj,
> -				  intel_dp->aux.ddc.dev.kobj.name);
>  	intel_connector_unregister(intel_connector);
>  }
>  
> -- 
> 2.4.3
> 
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Ville Syrjälä
Intel OTC
_______________________________________________
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http://lists.freedesktop.org/mailman/listinfo/intel-gfx

Re: [PATCH v8 2/2] drm/dp: Set aux.dev to the drm_connector device, instead of drm_device.

[Rafael Antognolli]

On Tue, Nov 24, 2015 at 10:31:41PM +0200, Ville Syrjälä wrote:
> On Mon, Nov 02, 2015 at 12:33:48PM -0800, Rafael Antognolli wrote:
> > So far, the i915 driver and some other drivers set it to the drm_device,
> > which doesn't allow one to know which DP a given aux channel is related
> > to. Changing this to be the drm_connector provides proper nesting, still
> > allowing one to get the drm_device from it. Some drivers already set it
> > to the drm_connector.
> > 
> > This also removes the need to add a sysfs link for the i2c device under
> > the connector, as it will already be there.
> > 
> > Signed-off-by: Rafael Antognolli <rafael.antognolli@intel.com>
> 
> I gave aux_dev a bit of a testing here, and it appaers to work quite
> splendidly.
> 
> This patch however causes lots of WARN spew if I unload the driver
> while in middle of dumping the DPCD via the aux_dev. It appears we
> we clean up things the wrong order now.

It looks like device_destroy is being called twice on the drm_aux_dev
and i2c adapter devices.

If I understood correctly, this is happening because I changed the
parent device, from the drm_device to the drm_connector, but the
drm_connector is being destroyed before the drm_aux_dev and i2c adapter
devices, which already causes them to be destroyed too.

Changing the drm_dp_aux_unregister() from inside intel_dp_aux_fini() to
intel_dp_connector_unregister(), right before
intel_connector_unregister(), seems to fix everything, and it still
makes sense in my opinion, since the auxdev is going to be unregistered
before we destroy the drm_connector. Do you think that would be ok?

> > ---
> >  drivers/gpu/drm/i915/intel_dp.c | 19 ++-----------------
> >  1 file changed, 2 insertions(+), 17 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index 8287df4..7aacc08 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -1078,36 +1078,21 @@ intel_dp_aux_init(struct intel_dp *intel_dp, struct intel_connector *connector)
> >  		intel_dp->aux_ch_ctl_reg = intel_dp->output_reg + 0x10;
> >  
> >  	intel_dp->aux.name = name;
> > -	intel_dp->aux.dev = dev->dev;
> > +	intel_dp->aux.dev = connector->base.kdev;
> >  	intel_dp->aux.transfer = intel_dp_aux_transfer;
> >  
> >  	DRM_DEBUG_KMS("registering %s bus for %s\n", name,
> >  		      connector->base.kdev->kobj.name);
> >  
> >  	ret = drm_dp_aux_register(&intel_dp->aux);
> > -	if (ret < 0) {
> > +	if (ret < 0)
> >  		DRM_ERROR("drm_dp_aux_register() for %s failed (%d)\n",
> >  			  name, ret);
> > -		return;
> > -	}
> > -
> > -	ret = sysfs_create_link(&connector->base.kdev->kobj,
> > -				&intel_dp->aux.ddc.dev.kobj,
> > -				intel_dp->aux.ddc.dev.kobj.name);
> > -	if (ret < 0) {
> > -		DRM_ERROR("sysfs_create_link() for %s failed (%d)\n", name, ret);
> > -		drm_dp_aux_unregister(&intel_dp->aux);
> > -	}
> >  }
> >  
> >  static void
> >  intel_dp_connector_unregister(struct intel_connector *intel_connector)
> >  {
> > -	struct intel_dp *intel_dp = intel_attached_dp(&intel_connector->base);
> > -
> > -	if (!intel_connector->mst_port)
> > -		sysfs_remove_link(&intel_connector->base.kdev->kobj,
> > -				  intel_dp->aux.ddc.dev.kobj.name);
> >  	intel_connector_unregister(intel_connector);
> >  }
> >  
> > -- 
> > 2.4.3
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Ville Syrjälä
> Intel OTC
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