On Fri, Oct 30, 2015 at 12:04:17PM +0200, Ville Syrjälä wrote:
> On Thu, Oct 29, 2015 at 04:23:45PM -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.
>
> Note that we (i915 folks at least) generally like to have the changelog
> in the commit message itself. So maybe move it here for the final
> version.
>
> Anyways, this is looking rather nice now. I spotted a few remaining style
> issues, and some error handling problems. Once those are dealt with
> I think we should be done.
>
> >
> > Signed-off-by: Rafael Antognolli <rafael.antognolli@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/Kconfig | 8 +
> > drivers/gpu/drm/Makefile | 1 +
> > drivers/gpu/drm/drm_dp_aux_dev.c | 381 +++++++++++++++++++++++++++++++++++++++
> > drivers/gpu/drm/drm_dp_helper.c | 5 +
> > include/drm/drm_dp_aux_dev.h | 50 +++++
> > 5 files changed, 445 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 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..16dbc2e
> > --- /dev/null
> > +++ b/drivers/gpu/drm/drm_dp_aux_dev.c
> > @@ -0,0 +1,381 @@
> > +/*
> > + * 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@xxxxxxxxx>
> > + *
> > + */
> > +
> > +#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;
> > +
> > +
>
> spurious newline
>
> > + 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 (count < 0)
> > + return -EINVAL;
>
> size_t is unsigned, so this can't happen.
>
> > +
> > + 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);
>
> Interesting. First time I've seen this stuff.
>
> > + 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 (count < 0)
> > + return -EINVAL;
>
> Another "size_t is unsigned" case.
>
> > +
> > + 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)
> > +
> > +/**
> > + * 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);
>
> You should use DRM_DEBUG and DRM_ERROR all around to conform to standard
> drm subsystem style.
>
> > + return 0;
> > +error:
> > + device_destroy(drm_dp_aux_dev_class,
> > + MKDEV(drm_dev_major, aux_dev->index));
> > + kfree(aux_dev);
>
> It was already added to the idr, so this needs something a bit more.
> Also in theory someone might have already opened the device by now.
>
> I guess you could just do a normal unregister here? I assume calling
> device_destroy() even though device_create() failed should be OK since
> you're already doing it, so having the unregister code do it instead
> should be equally fine.
I am not sure now why this device_destroy() is here, since if
device_create failed, there should be no need to destroy it. Maybe this
was left from previous versions and I forgot to remove it too during
those changes.
Shouldn't I just remove this part, and add the code to remove from the
idr?
> Oh and I guess we don't really need to store the struct device pointer
> under aux_dev since it's not used by anyone, not even by device_destroy().
>
> > + 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
> > + */
> > + 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.
> > + */
> > +int 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 0;
>
> Should we maybe return an error? Or maybe just make the function void
> since no one is likely to be interested in the return value?
>
> > +
> > + 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;
> > + device_destroy(drm_dp_aux_dev_class, MKDEV(drm_dev_major, minor));
> > +
> > + kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
> > + pr_debug("drm_dp_aux_dev: aux [%s] unregistered\n", aux->name);
>
> Can't dereference it safely after the kref_put().
>
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL(drm_dp_aux_unregister_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;
>
> Should class_destroy() in this error path.
>
> > + drm_dev_major = res;
> > +
> > + return 0;
> > +out:
> > + drm_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");
>
> Swap these around to be the opposite of init?
>
> > +}
> > +
> > +MODULE_AUTHOR("Rafael Antognolli <rafael.antognolli@xxxxxxxxx>");
> > +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..d2565cc 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 +769,9 @@ 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));
> >
> > + if (drm_dp_aux_register_devnode(aux))
> > + drm_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 +782,7 @@ 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@xxxxxxxxx>
> > + *
> > + */
> > +
> > +#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@xxxxxxxxxxxxxxxxxxxxx
> > http://lists.freedesktop.org/mailman/listinfo/dri-devel
>
> --
> Ville Syrjälä
> Intel OTC
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