From 6e3f797c9ae9bd381247e90907838da43f695306 Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Mon, 28 Sep 2015 21:46:35 +0200 Subject: drm/doc: Update docs about device instance setup ->load is deprecated, bus functions are deprecated and everyone should use drm_dev_alloc®ister. So update the .tmpl (and pull a bunch of the overview docs into the sourcecode to increase chances that it'll stay in sync in the future) and add notes to functions which are deprecated. I didn't bother to clean up and document the unload sequence similarly since that one is still a bit a mess: drm_dev_unregister does way too much, drm_unplug_dev does what _unregister should be doing but then has the complication of promising something it doesn't actually do (it doesn't unplug existing open fds for instance, only prevents new ones). Motivated since I don't want to hunt every new driver for usage of drm_platform_init any more ;-) v2: Reword the deprecation note for ->load a bit, using Laurent's suggestion as an example (but making the wording a bit stronger even). Fix spelling in commit message. v3: More spelling fixes from Laurent. Cc: Laurent Pinchart Cc: David Herrmann Acked-by: David Herrmann (v2) Signed-off-by: Daniel Vetter Signed-off-by: Daniel Vetter --- drivers/gpu/drm/drm_drv.c | 55 +++++++++++++++++++++++++++++++++++++++--- drivers/gpu/drm/drm_pci.c | 11 +++++++++ drivers/gpu/drm/drm_platform.c | 3 +++ 3 files changed, 65 insertions(+), 4 deletions(-) (limited to 'drivers') diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index 9ad823fcde87..d01f8d6c5fdb 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -396,16 +396,52 @@ void drm_minor_release(struct drm_minor *minor) drm_dev_unref(minor->dev); } +/** + * DOC: driver instance overview + * + * A device instance for a drm driver is represented by struct &drm_device. This + * is allocated with drm_dev_alloc(), usually from bus-specific ->probe() + * callbacks implemented by the driver. The driver then needs to initialize all + * the various subsystems for the drm device like memory management, vblank + * handling, modesetting support and intial output configuration plus obviously + * initialize all the corresponding hardware bits. An important part of this is + * also calling drm_dev_set_unique() to set the userspace-visible unique name of + * this device instance. Finally when everything is up and running and ready for + * userspace the device instance can be published using drm_dev_register(). + * + * There is also deprecated support for initalizing device instances using + * bus-specific helpers and the ->load() callback. But due to + * backwards-compatibility needs the device instance have to be published too + * early, which requires unpretty global locking to make safe and is therefore + * only support for existing drivers not yet converted to the new scheme. + * + * When cleaning up a device instance everything needs to be done in reverse: + * First unpublish the device instance with drm_dev_unregister(). Then clean up + * any other resources allocated at device initialization and drop the driver's + * reference to &drm_device using drm_dev_unref(). + * + * Note that the lifetime rules for &drm_device instance has still a lot of + * historical baggage. Hence use the reference counting provided by + * drm_dev_ref() and drm_dev_unref() only carefully. + * + * Also note that embedding of &drm_device is currently not (yet) supported (but + * it would be easy to add). Drivers can store driver-private data in the + * dev_priv field of &drm_device. + */ + /** * drm_put_dev - Unregister and release a DRM device * @dev: DRM device * * Called at module unload time or when a PCI device is unplugged. * - * Use of this function is discouraged. It will eventually go away completely. - * Please use drm_dev_unregister() and drm_dev_unref() explicitly instead. - * * Cleans up all DRM device, calling drm_lastclose(). + * + * Note: Use of this function is deprecated. It will eventually go away + * completely. Please use drm_dev_unregister() and drm_dev_unref() explicitly + * instead to make sure that the device isn't userspace accessible any more + * while teardown is in progress, ensuring that userspace can't access an + * inconsistent state. */ void drm_put_dev(struct drm_device *dev) { @@ -518,7 +554,9 @@ static void drm_fs_inode_free(struct inode *inode) * * Allocate and initialize a new DRM device. No device registration is done. * Call drm_dev_register() to advertice the device to user space and register it - * with other core subsystems. + * with other core subsystems. This should be done last in the device + * initialization sequence to make sure userspace can't access an inconsistent + * state. * * The initial ref-count of the object is 1. Use drm_dev_ref() and * drm_dev_unref() to take and drop further ref-counts. @@ -673,6 +711,12 @@ EXPORT_SYMBOL(drm_dev_unref); * * Never call this twice on any device! * + * NOTE: To ensure backward compatibility with existing drivers method this + * function calls the ->load() method after registering the device nodes, + * creating race conditions. Usage of the ->load() methods is therefore + * deprecated, drivers must perform all initialization before calling + * drm_dev_register(). + * * RETURNS: * 0 on success, negative error code on failure. */ @@ -720,6 +764,9 @@ EXPORT_SYMBOL(drm_dev_register); * Unregister the DRM device from the system. This does the reverse of * drm_dev_register() but does not deallocate the device. The caller must call * drm_dev_unref() to drop their final reference. + * + * This should be called first in the device teardown code to make sure + * userspace can't access the device instance any more. */ void drm_dev_unregister(struct drm_device *dev) { diff --git a/drivers/gpu/drm/drm_pci.c b/drivers/gpu/drm/drm_pci.c index 1b1bd42b0368..fcd2a86acd2c 100644 --- a/drivers/gpu/drm/drm_pci.c +++ b/drivers/gpu/drm/drm_pci.c @@ -266,6 +266,9 @@ void drm_pci_agp_destroy(struct drm_device *dev) * then register the character device and inter module information. * Try and register, if we fail to register, backout previous work. * + * NOTE: This function is deprecated, please use drm_dev_alloc() and + * drm_dev_register() instead and remove your ->load() callback. + * * Return: 0 on success or a negative error code on failure. */ int drm_get_pci_dev(struct pci_dev *pdev, const struct pci_device_id *ent, @@ -326,6 +329,10 @@ EXPORT_SYMBOL(drm_get_pci_dev); * Initializes a drm_device structures, registering the stubs and initializing * the AGP device. * + * NOTE: This function is deprecated. Modern modesetting drm drivers should use + * pci_register_driver() directly, this function only provides shadow-binding + * support for old legacy drivers on top of that core pci function. + * * Return: 0 on success or a negative error code on failure. */ int drm_pci_init(struct drm_driver *driver, struct pci_driver *pdriver) @@ -435,6 +442,10 @@ EXPORT_SYMBOL(drm_pci_init); * * Unregisters one or more devices matched by a PCI driver from the DRM * subsystem. + * + * NOTE: This function is deprecated. Modern modesetting drm drivers should use + * pci_unregister_driver() directly, this function only provides shadow-binding + * support for old legacy drivers on top of that core pci function. */ void drm_pci_exit(struct drm_driver *driver, struct pci_driver *pdriver) { diff --git a/drivers/gpu/drm/drm_platform.c b/drivers/gpu/drm/drm_platform.c index 5314c9d5fef4..644169e1a029 100644 --- a/drivers/gpu/drm/drm_platform.c +++ b/drivers/gpu/drm/drm_platform.c @@ -95,6 +95,9 @@ EXPORT_SYMBOL(drm_platform_set_busid); * subsystem, initializing a drm_device structure and calling the driver's * .load() function. * + * NOTE: This function is deprecated, please use drm_dev_alloc() and + * drm_dev_register() instead and remove your ->load() callback. + * * Return: 0 on success or a negative error code on failure. */ int drm_platform_init(struct drm_driver *driver, struct platform_device *platform_device) -- cgit v1.2.1