[Intel-gfx] [PATCH v5 1/2] drm/dp: Add a drm_aux-dev module for reading/writing dpcd registers.
Ville Syrjälä
ville.syrjala at linux.intel.com
Tue Oct 20 09:05:06 PDT 2015
On Fri, Oct 09, 2015 at 02:48:33PM -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_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.
>
> Signed-off-by: Rafael Antognolli <rafael.antognolli at 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 | 7 +
> include/drm/drm_dp_aux_dev.h | 50 ++++++
> 5 files changed, 439 insertions(+)
> 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 1a0a8df..64fa0f4 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 e814517..e5bc0ca 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..a2861e2
> --- /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 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 <asm/uaccess.h>
> +#include <drm/drm_dp_helper.h>
> +#include <drm/drm_crtc.h>
> +
> +struct drm_dp_aux_dev {
> + unsigned index;
> + struct drm_dp_aux *aux;
> + struct device *dev;
> + struct kref refcount;
> + bool removed;
> + spinlock_t removed_lock;
> +};
> +
> +#define DRM_AUX_MINORS 256
> +#define AUX_MAX_OFFSET (1 << 20)
> +static DEFINE_IDR(aux_idr);
> +static DEFINE_SPINLOCK(aux_idr_lock);
> +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;
> +
> + spin_lock(&aux_idr_lock);
> + aux_dev = idr_find(&aux_idr, index);
> + if (!kref_get_unless_zero(&aux_dev->refcount))
> + aux_dev = NULL;
> + spin_unlock(&aux_idr_lock);
> +
> + 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;
> + aux_dev->removed = false;
> + spin_lock_init(&aux_dev->removed_lock);
> + kref_init(&aux_dev->refcount);
> +
> + idr_preload(GFP_KERNEL);
> + spin_lock(&aux_idr_lock);
> + index = idr_alloc_cyclic(&aux_idr, aux_dev, 0, DRM_AUX_MINORS,
> + GFP_NOWAIT);
> + spin_unlock(&aux_idr_lock);
> + idr_preload_end();
With a mutex things would be simpler.
> + if (index < 0) {
> + kfree(aux_dev);
> + return ERR_PTR(-ENOMEM);
Can just pass the error value from idr_alloc_cyclic() upwards I think.
> + }
> + aux_dev->index = index;
> +
> + return aux_dev;
> +}
> +
> +static void free_drm_dp_aux_dev(struct drm_dp_aux_dev *aux_dev)
> +{
> + spin_lock(&aux_idr_lock);
> + idr_remove(&aux_idr, aux_dev->index);
> + spin_unlock(&aux_idr_lock);
I think the idr_remove should be done when unregistering the aux_dev,
that way no one can open it anymore after it's gone.
> + kfree(aux_dev);
> +}
> +
> +static void release_drm_dp_aux_dev(struct kref *ref)
> +{
> + int minor;
> + struct drm_dp_aux_dev *aux_dev =
> + container_of(ref, struct drm_dp_aux_dev, refcount);
> + minor = aux_dev->index;
> + device_destroy(drm_dp_aux_dev_class, MKDEV(drm_dev_major, minor));
device_destroy() should also be done when unregisteing I think.
> +
> + free_drm_dp_aux_dev(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;
> + bool aux_removed;
> +
> + if (count < 0)
> + return -EINVAL;
> +
> + spin_lock(&aux_dev->removed_lock);
> + aux_removed = aux_dev->removed;
> + spin_unlock(&aux_dev->removed_lock);
> + if (aux_removed)
> + return -ENODEV;
Hmm. This seems racy still. aux_dev will now stay around until the file
is closed, but the actual aux helper backing it may still disappear at
any time. I don't think we want to hold a lock around the whole thing,
cause I have a feeling that way lies lockdep issues. So maybe we need
some kinda atomic use counter here, or something?
read()
{
if (atomic_inc_unless_zero(usecount))
return -...;
...
atomic_dec();
wake_up();
}
unregister()
{
idr_remove();
atomic_dec(usecount);
wait_event(usecount == 0);
kref_put();
}
register()
{
...
atomic_set(usecount, 1);
idr_alloc_cyclic();
}
I guess another option would to just wait for all fds to be closed in a
similar fashion. But that seems like a more open ended wait.
> +
> + bytes_pending = min((loff_t)count, AUX_MAX_OFFSET - (*offset));
> +
> + if (!access_ok(VERIFY_WRITE, buf, bytes_pending))
> + return -EFAULT;
> +
> + while (bytes_pending > 0) {
> + uint8_t localbuf[DP_AUX_MAX_PAYLOAD_BYTES];
> + ssize_t res;
> + ssize_t todo = min(bytes_pending, sizeof(localbuf));
> +
> + res = drm_dp_dpcd_read(aux_dev->aux, *offset, localbuf, todo);
> + if (res <= 0)
> + return num_bytes_processed ? num_bytes_processed : res;
> + if (__copy_to_user(buf + num_bytes_processed, localbuf, res))
> + return num_bytes_processed ?
> + num_bytes_processed : -EFAULT;
> + bytes_pending -= res;
> + *offset += res;
> + num_bytes_processed += res;
> + }
> +
> + return num_bytes_processed;
> +}
> +
> +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;
> + bool aux_removed;
> +
> + if (count < 0)
> + return -EINVAL;
> +
> + spin_lock(&aux_dev->removed_lock);
> + aux_removed = aux_dev->removed;
> + spin_unlock(&aux_dev->removed_lock);
> + if (aux_removed)
> + return -ENODEV;
> +
> + bytes_pending = min((loff_t)count, AUX_MAX_OFFSET - *offset);
> +
> + if (!access_ok(VERIFY_READ, buf, bytes_pending))
> + return -EFAULT;
> +
> + while (bytes_pending > 0) {
> + uint8_t localbuf[DP_AUX_MAX_PAYLOAD_BYTES];
> + ssize_t res;
> + ssize_t todo = min(bytes_pending, sizeof(localbuf));
> +
> + if (__copy_from_user(localbuf,
> + buf + num_bytes_processed, todo)) {
> + return num_bytes_processed ?
> + num_bytes_processed : -EFAULT;
> + }
> +
> + res = drm_dp_dpcd_write(aux_dev->aux, *offset, localbuf, todo);
> + if (res <= 0) {
> + return num_bytes_processed ? num_bytes_processed : res;
> + }
> + bytes_pending -= res;
> + *offset += res;
> + num_bytes_processed += res;
> + }
> +
> + return num_bytes_processed;
> +}
> +
> +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)
> +
> +/**
> + * 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);
> + goto error;
> + }
> +
> + pr_debug("drm_dp_aux_dev: aux [%s] registered as minor %d\n",
> + aux->name, aux_dev->index);
> + return 0;
> +error:
> + free_drm_dp_aux_dev(aux_dev);
> + return res;
> +}
> +EXPORT_SYMBOL(drm_dp_aux_register_devnode);
> +
> +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 */
> + spin_lock(&aux_idr_lock);
> + idr_for_each_entry(&aux_idr, iter, id) {
> + if (iter->aux == aux) {
> + aux_dev = iter;
> + break;
> + }
> + }
> + spin_unlock(&aux_idr_lock);
> + return aux_dev;
> +}
> +
> +/**
> + * 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.
> + */
> +int drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux)
> +{
> + struct drm_dp_aux_dev *aux_dev;
> +
> + aux_dev = drm_dp_aux_dev_get_by_aux(aux);
> + if (!aux_dev) /* attach must have failed */
> + return 0;
> +
> + spin_lock(&aux_dev->removed_lock);
> + aux_dev->removed = true;
> + spin_unlock(&aux_dev->removed_lock);
> +
> + kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
> + pr_debug("drm_dp_aux_dev: aux [%s] unregistered\n", aux->name);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(drm_dp_aux_unregister_devnode);
> +
> +static int __init drm_dp_aux_dev_init(void)
> +{
> + int res;
> +
> + res = register_chrdev(0, "aux", &auxdev_fops);
As soon as this returns someone can open the device, so seems like this
should be the last thing we do.
> + if (res < 0)
> + goto out;
> + drm_dev_major = 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_unreg_chrdev;
> + }
> + drm_dp_aux_dev_class->dev_groups = drm_dp_aux_groups;
> +
> + idr_init(&aux_idr);
AFAIK no need to init it since you used DEFINE_IDR()
> +
> + 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_dp_aux_dev_exit(void)
> +{
> + class_destroy(drm_dp_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 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..e50f65d 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>
>
> /**
> @@ -768,6 +769,11 @@ 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));
>
> +
Looks like an extra newline we don't need.
> + if (drm_dp_aux_register_devnode(aux))
> + printk(KERN_ERR "%s: Could not register drm_dp_aux_dev.\n",
> + __FILE__);
> +
> return i2c_add_adapter(&aux->ddc);
> }
> EXPORT_SYMBOL(drm_dp_aux_register);
> @@ -778,6 +784,7 @@ 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..35409a2
> --- /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 at 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);
> +int 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 int drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux)
> +{
> + return 0;
> +}
> +
> +#endif
> +
> +#endif
> --
> 2.4.3
>
> _______________________________________________
> dri-devel mailing list
> dri-devel at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel
--
Ville Syrjälä
Intel OTC
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