On Fri, 8 May 2020 16:53:41 +0300 Alexandru Ardelean <[email protected]> wrote:
> The aim of this is to reduce the organization violation of ioctl() calls in > IIO core. Currently, since the chardev is split across files, event ioctl() > calls need to be called in buffer ioctl() calls. > > The 'industrialio-core.c' file will provide a 'iio_device_ioctl()' which > will iterate over a list of ioctls registered with the IIO device. These > can be event ioctl() or buffer ioctl() calls, or something else. > This is needed, since there is currently one chardev per IIO device and > that is used for both event handling and reading from the buffer. > > Each ioctl() will have to return a IIO_IOCTL_UNHANDLED code (which is > positive 1), if the ioctl() did not handle the call in any. This eliminates > any potential ambiguities; if we were to have used error codes it would > have been uncertain whether they were actual errors, or whether > the registered ioctl() doesn't service the command. > > If any ioctl() returns 0, it was considered that it was serviced > successfully and the loop will exit. > > One assumption for all registered ioctl() handlers is that they are > statically allocated, so the iio_device_unregister() which just remove all > of them from the device's ioctl() handler list. > > Also, something that is a bit hard to do [at this point] and may not be > worth the effort of doing, is to check whether registered ioctl() > calls/commands overlap. This should be unlikely to happen, and should get > caught at review time. Though, new ioctl() calls would likely not be added > too often. > > Signed-off-by: Alexandru Ardelean <[email protected]> We seem to have dropped the locking in here. What am I missing that stops us racing a remove with the ioctl? If there is a reason that can't race, please add comments there so I don't wonders sometime in the future. The check on iio_dev->info means we won't start the ioctl if the remove has been called, but if we switch immediately after that, anything can happen before we start calling the ioctls. J > --- > drivers/iio/iio_core.h | 14 ++++++++++++++ > drivers/iio/industrialio-core.c | 33 +++++++++++++++++++++++++++++++++ > include/linux/iio/iio.h | 2 ++ > 3 files changed, 49 insertions(+) > > diff --git a/drivers/iio/iio_core.h b/drivers/iio/iio_core.h > index a527a66be9e5..34c3e19229d8 100644 > --- a/drivers/iio/iio_core.h > +++ b/drivers/iio/iio_core.h > @@ -17,6 +17,20 @@ struct iio_dev; > > extern struct device_type iio_device_type; > > +#define IIO_IOCTL_UNHANDLED 1 > +struct iio_ioctl_handler { > + struct list_head entry; > + long (*ioctl)(struct iio_dev *indio_dev, struct file *filp, > + unsigned int cmd, unsigned long arg); > +}; > + > +long iio_device_ioctl(struct iio_dev *indio_dev, struct file *filp, > + unsigned int cmd, unsigned long arg); > + > +void iio_device_ioctl_handler_register(struct iio_dev *indio_dev, > + struct iio_ioctl_handler *h); > +void iio_device_ioctl_handler_unregister(struct iio_ioctl_handler *h); > + > int __iio_add_chan_devattr(const char *postfix, > struct iio_chan_spec const *chan, > ssize_t (*func)(struct device *dev, > diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c > index 32e045c7f0c1..5df3af5e7dcb 100644 > --- a/drivers/iio/industrialio-core.c > +++ b/drivers/iio/industrialio-core.c > @@ -1534,6 +1534,7 @@ struct iio_dev *iio_device_alloc(int sizeof_priv) > } > dev_set_name(&dev->dev, "iio:device%d", dev->id); > INIT_LIST_HEAD(&dev->buffer_list); > + INIT_LIST_HEAD(&dev->ioctl_handlers); > > return dev; > } > @@ -1587,6 +1588,33 @@ struct iio_dev *devm_iio_device_alloc(struct device > *dev, int sizeof_priv) > } > EXPORT_SYMBOL_GPL(devm_iio_device_alloc); > > +void iio_device_ioctl_handler_register(struct iio_dev *indio_dev, > + struct iio_ioctl_handler *h) > +{ > + /* this assumes that all ioctl() handlers are statically allocated */ > + list_add_tail(&h->entry, &indio_dev->ioctl_handlers); > +} > + > +long iio_device_ioctl(struct iio_dev *indio_dev, struct file *filp, > + unsigned int cmd, unsigned long arg) > +{ > + struct iio_ioctl_handler *h; > + int ret; > + > + if (!indio_dev->info) > + return -ENODEV; The locking is gone? > + > + list_for_each_entry(h, &indio_dev->ioctl_handlers, entry) { > + ret = h->ioctl(indio_dev, filp, cmd, arg); > + if (ret == 0) > + return 0; > + if (ret != IIO_IOCTL_UNHANDLED) > + return ret; > + } > + > + return -EINVAL; > +} > + > static int iio_check_unique_scan_index(struct iio_dev *indio_dev) > { > int i, j; > @@ -1722,6 +1750,8 @@ EXPORT_SYMBOL(__iio_device_register); > **/ > void iio_device_unregister(struct iio_dev *indio_dev) > { > + struct iio_ioctl_handler *h, *t; > + > cdev_device_del(indio_dev->chrdev, &indio_dev->dev); > iio_device_free_chrdev_id(&indio_dev->dev); > > @@ -1731,6 +1761,9 @@ void iio_device_unregister(struct iio_dev *indio_dev) > > iio_disable_all_buffers(indio_dev); > > + list_for_each_entry_safe(h, t, &indio_dev->ioctl_handlers, entry) > + list_del(&h->entry); > + > indio_dev->info = NULL; > > iio_device_wakeup_eventset(indio_dev); > diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h > index 52992be44e9e..b6ca8d85629e 100644 > --- a/include/linux/iio/iio.h > +++ b/include/linux/iio/iio.h > @@ -488,6 +488,7 @@ struct iio_buffer_setup_ops { > * @currentmode: [DRIVER] current operating mode > * @dev: [DRIVER] device structure, should be assigned a parent > * and owner > + * @ioctl_handlers: [INTERN] list of registered ioctl handlers > * @event_interface: [INTERN] event chrdevs associated with interrupt lines > * @buffer: [DRIVER] any buffer present > * @buffer_list: [INTERN] list of all buffers currently attached > @@ -529,6 +530,7 @@ struct iio_dev { > int modes; > int currentmode; > struct device dev; > + struct list_head ioctl_handlers; > > struct iio_event_interface *event_interface; >
