Re: [PATCH RFC v2 3/3] drm/dp: Add a drm_aux-dev module for reading/writing dpcd registers.

On Tue, Sep 15, 2015 at 04:55:04PM -0700, Rafael Antognolli wrote:

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: read and write. The address of the register to be read or written is given using lseek. Reading or writing does not update the offset of the file.

I think not updating the read position is very surprising. Would it be hard to fix that? -Daniel

Signed-off-by: Rafael Antognolli rafael.antognolli@intel.com

drivers/gpu/drm/Kconfig | 4 + drivers/gpu/drm/Makefile | 1 + drivers/gpu/drm/drm_aux-dev.c | 326 ++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 331 insertions(+) create mode 100644 drivers/gpu/drm/drm_aux-dev.c

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..fcc334a --- /dev/null +++ b/drivers/gpu/drm/drm_aux-dev.c @@ -0,0 +1,326 @@ +/*

• • 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 <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 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 ssize_t auxdev_read(struct file *file, char __user *buf, size_t count,

• 	   loff_t *offset)
  

+{

• char *localbuf;
• ssize_t res;
• struct drm_aux_dev *aux_dev = file->private_data;
• localbuf = memdup_user(buf, count);
• if (IS_ERR(localbuf))

• return PTR_ERR(buf);
  

• res = drm_dp_dpcd_read(aux_dev->aux, *offset, localbuf, count);
• if (res < 0)

• goto finish;
  

• if (copy_to_user(buf, localbuf, res))

• res = -EFAULT;
  

+finish:

• kfree(localbuf);
• return res;

+}

+static ssize_t auxdev_write(struct file *file, const char __user *buf,

• 	    size_t count, loff_t *offset)
  

+{

• char *localbuf;
• ssize_t res;
• struct drm_aux_dev *aux_dev = file->private_data;
• localbuf = memdup_user(buf, count);
• if (IS_ERR(localbuf))

• return PTR_ERR(buf);
  

• res = drm_dp_dpcd_write(aux_dev->aux, *offset, localbuf, count);
• kfree(localbuf);
• return res;

+}

+static const struct file_operations auxdev_fops = {

• .owner = THIS_MODULE,
• .llseek = generic_file_llseek,
• .read = auxdev_read,
• .write = auxdev_write,
• .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_inform_cb(int action, struct drm_dp_aux *aux) +{

• 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 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 */
• drm_dp_aux_set_aux_dev(&auxdev_inform_cb);
• /* Bind to already existing DP aux */
• res = drm_dp_aux_for_each(&drm_dev_major, auxdev_attach_aux);
• return 0;

+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_set_aux_dev(NULL);
• 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@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);

2.4.3

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