linux内核radeon gpu源码解析4 —— drm_get_pci_dev函数详解1

上一篇讲到了drm_get_pci_dev函数，这是一个比较关键的函数，其中调用了几个函数，现在一一进行详细说明。再把函数的完整代码贴出来，在drivers/gpu/drm/drm_pci.c中：

/**
 * drm_get_pci_dev - Register a PCI device with the DRM subsystem
 * @pdev: PCI device
 * @ent: entry from the PCI ID table that matches @pdev
 * @driver: DRM device driver
 *
 * Attempt to gets inter module "drm" information. If we are first
 * 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 &drm_driver.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,
		    struct drm_driver *driver)
{
	struct drm_device *dev;
	int ret;

	DRM_DEBUG("\n");

	dev = drm_dev_alloc(driver, &pdev->dev);
	if (IS_ERR(dev))
		return PTR_ERR(dev);

	ret = pci_enable_device(pdev);
	if (ret)
		goto err_free;

	dev->pdev = pdev;
#ifdef __alpha__
	dev->hose = pdev->sysdata;
#endif

	if (drm_core_check_feature(dev, DRIVER_MODESET))
		pci_set_drvdata(pdev, dev);

	drm_pci_agp_init(dev);

	ret = drm_dev_register(dev, ent->driver_data);
	if (ret)
		goto err_agp;

	/* No locking needed since shadow-attach is single-threaded since it may
	 * only be called from the per-driver module init hook. */
	if (drm_core_check_feature(dev, DRIVER_LEGACY))
		list_add_tail(&dev->legacy_dev_list, &driver->legacy_dev_list);

	return 0;

err_agp:
	drm_pci_agp_destroy(dev);
	pci_disable_device(pdev);
err_free:
	drm_dev_put(dev);
	return ret;
}
EXPORT_SYMBOL(drm_get_pci_dev);

先说第1个函数：drm_dev_alloc。

调用处：dev = drm_dev_alloc(driver, &pdev->dev);

源码如下：

drivers/gpu/drm/drm_drv.c

/**
 * drm_dev_alloc - Allocate new DRM device
 * @driver: DRM driver to allocate device for
 * @parent: Parent device object
 *
 * 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. 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_get() and
 * drm_dev_put() to take and drop further ref-counts.
 *
 * Note that for purely virtual devices @parent can be NULL.
 *
 * Drivers that wish to subclass or embed &struct drm_device into their
 * own struct should look at using drm_dev_init() instead.
 *
 * RETURNS:
 * Pointer to new DRM device, or ERR_PTR on failure.
 */
struct drm_device *drm_dev_alloc(struct drm_driver *driver,
				 struct device *parent)
{
	struct drm_device *dev;
	int ret;
 
	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
	if (!dev)
		return ERR_PTR(-ENOMEM);
 
	ret = drm_dev_init(dev, driver, parent);
	if (ret) {
		kfree(dev);
		return ERR_PTR(ret);
	}
 
	return dev;
}
EXPORT_SYMBOL(drm_dev_alloc);

这个函数的参数struct drm_driver *driver其实就是指向了kms_driver。

函数完成的事情也挺好理解，就是先分配了一个struct drm_device 结构，并使用dev指向这个结构，其实就是新建了一个drm设备。

接下来调用drm_dev_init函数对于这个新建的设备进行初始化。代码如下：

drivers/gpu/drm/drm_drv.c：

/**
 * drm_dev_init - Initialise new DRM device
 * @dev: DRM device
 * @driver: DRM driver
 * @parent: Parent device object
 *
 * 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. 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_get() and
 * drm_dev_put() to take and drop further ref-counts.
 *
 * Note that for purely virtual devices @parent can be NULL.
 *
 * Drivers that do not want to allocate their own device struct
 * embedding &struct drm_device can call drm_dev_alloc() instead. For drivers
 * that do embed &struct drm_device it must be placed first in the overall
 * structure, and the overall structure must be allocated using kmalloc(): The
 * drm core's release function unconditionally calls kfree() on the @dev pointer
 * when the final reference is released. To override this behaviour, and so
 * allow embedding of the drm_device inside the driver's device struct at an
 * arbitrary offset, you must supply a &drm_driver.release callback and control
 * the finalization explicitly.
 *
 * RETURNS:
 * 0 on success, or error code on failure.
 */
int drm_dev_init(struct drm_device *dev,
		 struct drm_driver *driver,
		 struct device *parent)
{
	int ret;

	if (!drm_core_init_complete) {
		DRM_ERROR("DRM core is not initialized\n");
		return -ENODEV;
	}

	kref_init(&dev->ref);
	dev->dev = get_device(parent);
	dev->driver = driver;

	INIT_LIST_HEAD(&dev->filelist);
	INIT_LIST_HEAD(&dev->filelist_internal);
	INIT_LIST_HEAD(&dev->clientlist);
	INIT_LIST_HEAD(&dev->ctxlist);
	INIT_LIST_HEAD(&dev->vmalist);
	INIT_LIST_HEAD(&dev->maplist);
	INIT_LIST_HEAD(&dev->vblank_event_list);

	spin_lock_init(&dev->buf_lock);
	spin_lock_init(&dev->event_lock);
	mutex_init(&dev->struct_mutex);
	mutex_init(&dev->filelist_mutex);
	mutex_init(&dev->clientlist_mutex);
	mutex_init(&dev->ctxlist_mutex);
	mutex_init(&dev->master_mutex);

	dev->anon_inode = drm_fs_inode_new();
	if (IS_ERR(dev->anon_inode)) {
		ret = PTR_ERR(dev->anon_inode);
		DRM_ERROR("Cannot allocate anonymous inode: %d\n", ret);
		goto err_free;
	}

	if (drm_core_check_feature(dev, DRIVER_RENDER)) {
		ret = drm_minor_alloc(dev, DRM_MINOR_RENDER);
		if (ret)
			goto err_minors;
	}

	ret = drm_minor_alloc(dev, DRM_MINOR_PRIMARY);
	if (ret)
		goto err_minors;

	ret = drm_ht_create(&dev->map_hash, 12);
	if (ret)
		goto err_minors;

	drm_legacy_ctxbitmap_init(dev);

	if (drm_core_check_feature(dev, DRIVER_GEM)) {
		ret = drm_gem_init(dev);
		if (ret) {
			DRM_ERROR("Cannot initialize graphics execution manager (GEM)\n");
			goto err_ctxbitmap;
		}
	}

	/* Use the parent device name as DRM device unique identifier, but fall
	 * back to the driver name for virtual devices like vgem. */
	ret = drm_dev_set_unique(dev, parent ? dev_name(parent) : driver->name);
	if (ret)
		goto err_setunique;

	return 0;

err_setunique:
	if (drm_core_check_feature(dev, DRIVER_GEM))
		drm_gem_destroy(dev);
err_ctxbitmap:
	drm_legacy_ctxbitmap_cleanup(dev);
	drm_ht_remove(&dev->map_hash);
err_minors:
	drm_minor_free(dev, DRM_MINOR_PRIMARY);
	drm_minor_free(dev, DRM_MINOR_RENDER);
	drm_fs_inode_free(dev->anon_inode);
err_free:
	put_device(dev->dev);
	mutex_destroy(&dev->master_mutex);
	mutex_destroy(&dev->ctxlist_mutex);
	mutex_destroy(&dev->clientlist_mutex);
	mutex_destroy(&dev->filelist_mutex);
	mutex_destroy(&dev->struct_mutex);
	return ret;
}
EXPORT_SYMBOL(drm_dev_init);

函数说明已经说得很清楚了，drm_dev_init函数初始化了一个新的DRM设备。其实就是给上边新分配的struct drm_device *dev赋值。

传入的参数在这两句程序中用到：

dev->dev = get_device(parent);
dev->driver = driver;
其余的注意事项在函数注释中也已经说得很清楚了，直接看函数注释就好，这里就不再翻译成中文了。

通过drm_dev_alloc函数中的drm_dev_init函数和drm_get_pci_dev 函数中的drm_dev_register函数，DRM框架为我们做了如下事情：

• 创建设备节点：/dev/dri/card0
• 创建sysfs节点：/sys/class/drm/card0
• 创建debugfs节点：/sys/kernel/debug/dri/0

参考资料：

DRM驱动程序开发（VKMS）（DRM 驱动程序开发（VKMS）_何小龙的博客-CSDN博客_/dev/dri/card0）