Thanks Ville for the review, I'm addressing all the issues but have some
questions on the ones mentioned below:
On Tue, Sep 29, 2015 at 05:09:23PM +0300, Ville Syrjälä wrote:
> On Mon, Sep 28, 2015 at 04:45:36PM -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@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/Kconfig | 8 +
> > drivers/gpu/drm/Makefile | 1 +
> > drivers/gpu/drm/drm_dp_aux_dev.c | 357 +++++++++++++++++++++++++++++++++++++++
> > drivers/gpu/drm/drm_dp_helper.c | 5 +
> > include/drm/drm_dp_aux_dev.h | 50 ++++++
> > 5 files changed, 421 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 45e7719..e5ae7f0 100644
> > --- a/drivers/gpu/drm/Makefile
> > +++ b/drivers/gpu/drm/Makefile
> > @@ -25,6 +25,7 @@ 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..e337081
> > --- /dev/null
> > +++ b/drivers/gpu/drm/drm_dp_aux_dev.c
> > @@ -0,0 +1,357 @@
> > +/*
> > + * 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 <asm/uaccess.h>
> > +#include <drm/drm_dp_helper.h>
> > +#include <drm/drm_crtc.h>
> > +
> > +struct drm_dp_aux_dev {
> > + struct list_head list;
> > + unsigned index;
> > + struct drm_dp_aux *aux;
> > + struct device *dev;
> > +};
> > +
> > +#define DRM_AUX_MINORS 256
> > +static int aux_max_offset = 1 << 20;
>
> People seem to prefer defines for such things.
>
> > +static int drm_dp_aux_dev_count = 0;
> > +static LIST_HEAD(drm_dp_aux_dev_list);
> > +static DEFINE_SPINLOCK(drm_dp_aux_dev_list_lock);
> > +
> > +static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_minor(unsigned index)
> > +{
> > + struct drm_dp_aux_dev *aux_dev;
> > +
> > + spin_lock(&drm_dp_aux_dev_list_lock);
> > + list_for_each_entry(aux_dev, &drm_dp_aux_dev_list, list) {
> > + if (aux_dev->index == index)
> > + goto found;
> > + }
> > +
> > + aux_dev = NULL;
> > +found:
> > + spin_unlock(&drm_dp_aux_dev_list_lock);
> > + return aux_dev;
> > +}
> > +
> > +static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_aux(struct drm_dp_aux *aux)
> > +{
> > + struct drm_dp_aux_dev *aux_dev;
> > +
> > + spin_lock(&drm_dp_aux_dev_list_lock);
> > + list_for_each_entry(aux_dev, &drm_dp_aux_dev_list, list) {
> > + if (aux_dev->aux == aux)
> > + goto found;
> > + }
> > +
> > + aux_dev = NULL;
> > +found:
> > + spin_unlock(&drm_dp_aux_dev_list_lock);
> > + return aux_dev;
> > +}
> > +
> > +static struct drm_dp_aux_dev *get_free_drm_dp_aux_dev(struct drm_dp_aux *aux)
> > +{
> > + struct drm_dp_aux_dev *aux_dev;
> > + int index;
> > +
> > + spin_lock(&drm_dp_aux_dev_list_lock);
> > + index = drm_dp_aux_dev_count;
> > + spin_unlock(&drm_dp_aux_dev_list_lock);
> > + if (index >= DRM_AUX_MINORS) {
> > + printk(KERN_ERR "drm_dp_aux_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_dp_aux_dev_list_lock);
> > + drm_dp_aux_dev_count++;
>
> That's racy. Someone else could have snuck in and pushed
> drm_dp_aux_dev_count over the limit already.
>
> Maybe we want to use an idr or something to allocate the
> index?
>
> > + list_add_tail(&aux_dev->list, &drm_dp_aux_dev_list);
> > + spin_unlock(&drm_dp_aux_dev_list_lock);
> > + return aux_dev;
> > +}
> > +
> > +static void return_drm_dp_aux_dev(struct drm_dp_aux_dev *aux_dev)
> > +{
> > + spin_lock(&drm_dp_aux_dev_list_lock);
> > + list_del(&aux_dev->list);
> > + spin_unlock(&drm_dp_aux_dev_list_lock);
> > + kfree(aux_dev);
> > +}
>
> I'm not a fan of the get_free & return names. Maybe just alloc/free?
>
> > +
> > +static ssize_t name_show(struct device *dev,
> > + struct device_attribute *attr, char *buf)
> > +{
> > + struct drm_dp_aux_dev *aux_dev =
> > + drm_dp_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_dp_aux_dev *aux_dev =
> > + drm_dp_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_dp_aux_attrs[] = {
> > + &dev_attr_name.attr,
> > + &dev_attr_connector.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)
> > +{
> > + ssize_t bytes_pending, num_bytes_processed = 0;
> > + struct drm_dp_aux_dev *aux_dev = file->private_data;
> > +
> > + bytes_pending = aux_max_offset - *offset;
> > + bytes_pending = count < bytes_pending ? count : bytes_pending;
>
> I would write it as
> bytes_pending = min(count, aux_max_offset - *offset);
>
> > + if (bytes_pending < 0)
> > + return -EFAULT;
>
> Can this actually happen somehow?
I believe the "count" argument could be negative, not sure if the kernel
does any checks on that. Still have to look that up. But if that's the
case, I could just check for count < 0 earlier on, right?
> > +
> > + if (!access_ok(VERIFY_WRITE, buf, bytes_pending))
> > + return -EFAULT;
> > +
> > + while (bytes_pending > 0) {
> > + uint8_t localbuf[DP_AUX_MAX_PAYLOAD_BYTES];
> > + ssize_t todo = sizeof(localbuf);
> > + ssize_t res;
> > + todo = bytes_pending < todo ? bytes_pending : todo;
>
> Would write it as
> 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;
> > + }
>
> Could drop the extra {}
>
> > + if (__copy_to_user(buf + num_bytes_processed, localbuf, res)) {
> > + return num_bytes_processed ?
> > + num_bytes_processed : -EFAULT;
> > + }
>
> ditto
>
> > + 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)
> > +{
> > + ssize_t bytes_pending, num_bytes_processed = 0;
> > + struct drm_dp_aux_dev *aux_dev = file->private_data;
> > +
> > + bytes_pending = aux_max_offset - *offset;
> > + bytes_pending = count < bytes_pending ? count : bytes_pending;
> > + if (bytes_pending < 0)
> > + return -EFAULT;
> > +
> > + if (!access_ok(VERIFY_READ, buf, bytes_pending))
> > + return -EFAULT;
> > +
> > + while (bytes_pending > 0) {
> > + uint8_t localbuf[DP_AUX_MAX_PAYLOAD_BYTES];
> > + ssize_t todo = sizeof(localbuf);
> > + ssize_t res;
> > + todo = bytes_pending < todo ? bytes_pending : todo;
> > + 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;
> > + }
>
> same comments for write as for read.
>
> > + bytes_pending -= res;
> > + *offset += res;
> > + num_bytes_processed += res;
> > + }
> > +
> > + return num_bytes_processed;
> > +}
> > +
> > +static const struct file_operations auxdev_fops = {
> > + .owner = THIS_MODULE,
> > + .llseek = auxdev_llseek,
> > + .read = auxdev_read,
> > + .write = auxdev_write,
> > + .open = auxdev_open,
> > +};
> > +
> > +static struct class *drm_dp_aux_dev_class;
> > +static int drm_dev_major = -1;
> > +
> > +#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 = get_free_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:
> > + return_drm_dp_aux_dev(aux_dev);
> > + return res;
> > +
> > +}
> > +
> > +/**
> > + * 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)
> > +{
> > + int minor;
> > + 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;
> > +
> > + minor = aux_dev->index;
> > + return_drm_dp_aux_dev(aux_dev);
> > + device_destroy(drm_dp_aux_dev_class, MKDEV(drm_dev_major, minor));
>
> device_destroy before you free the auxdev seem safer.
>
> What happens if someone has the device still open? Do we need to kref the
> aux_dev and add some kind of dead flag or something?
Yeah, I couldn't find anything that says the device would stay around
while the file is still open, so I guess you are right. So, I would need
to put some locks around the aux_dev usage too, right?
> > +
> > + pr_debug("drm_dp_aux_dev: aux [%s] unregistered\n", aux->name);
> > + return 0;
> > +}
> > +
> > +static int __init drm_dp_aux_dev_init(void)
> > +{
> > + int res;
> > +
> > + printk(KERN_INFO "drm dp aux /dev entries driver\n");
>
> I don't see much point in this printk.
>
> > +
> > + res = register_chrdev(0, "aux", &auxdev_fops);
> > + 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;
> > +
> > + 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)
> > +{
> > + printk(KERN_INFO "drm dp aux /dev entries driver - unloading\n");
>
> ditto
>
> > + class_destroy(drm_dp_aux_dev_class);
> > + unregister_chrdev(drm_dev_major, "aux");
> > +}
> > +
> > +MODULE_AUTHOR("Rafael Antognolli <rafael.antognolli@xxxxxxxxx>");
> > +MODULE_DESCRIPTION("DRM DP AUX /dev entries driver");
> > +MODULE_LICENSE("GPL");
>
> Doesn't match your license boilerplate.
So, should it be "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..f3a2eb0 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));
> >
> > +
> > + drm_dp_aux_register_devnode(aux);
> > +
> > 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..77534e8
> > --- /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 _UAPI_LINUX_DRM_DP_AUX_DEV_
> > +#define _UAPI_LINUX_DRM_DP_AUX_DEV_
>
> Not uapi.
>
> #ifndef DRM_DP_AUX_DEV_H
> #define ...
> would seem line enough.
>
> > +
> > +#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
Thanks,
Rafael
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