linux/drivers/gpu/drm/drm_platform.c
David Herrmann 099d1c290e drm: provide device-refcount
Lets not trick ourselves into thinking "drm_device" objects are not
ref-counted. That's just utterly stupid. We manage "drm_minor" objects on
each drm-device and each minor can have an unlimited number of open
handles. Each of these handles has the drm_minor (and thus the drm_device)
as private-data in the file-handle. Therefore, we may not destroy
"drm_device" until all these handles are closed.

It is *not* possible to reset all these pointers atomically and restrict
access to them, and this is *not* how this is done! Instead, we use
ref-counts to make sure the object is valid and not freed.

Note that we currently use "dev->open_count" for that, which is *exactly*
the same as a reference-count, just open coded. So this patch doesn't
change any semantics on DRM devices (well, this patch just introduces the
ref-count, anyway. Follow-up patches will replace open_count by it).

Also note that generic VFS revoke support could allow us to drop this
ref-count again. We could then just synchronously disable any fops->xy()
calls. However, this is not the case, yet, and no such patches are
in sight (and I seriously question the idea of dropping the ref-cnt
again).

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
2014-03-16 12:25:17 +01:00

153 lines
4.1 KiB
C

/*
* Derived from drm_pci.c
*
* Copyright 2003 José Fonseca.
* Copyright 2003 Leif Delgass.
* Copyright (c) 2009, Code Aurora Forum.
* All Rights Reserved.
*
* 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 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.
*/
#include <linux/export.h>
#include <drm/drmP.h>
/*
* Register.
*
* \param platdev - Platform device struture
* \return zero on success or a negative number on failure.
*
* 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.
*/
static int drm_get_platform_dev(struct platform_device *platdev,
struct drm_driver *driver)
{
struct drm_device *dev;
int ret;
DRM_DEBUG("\n");
dev = drm_dev_alloc(driver, &platdev->dev);
if (!dev)
return -ENOMEM;
dev->platformdev = platdev;
ret = drm_dev_register(dev, 0);
if (ret)
goto err_free;
DRM_INFO("Initialized %s %d.%d.%d %s on minor %d\n",
driver->name, driver->major, driver->minor, driver->patchlevel,
driver->date, dev->primary->index);
return 0;
err_free:
drm_dev_unref(dev);
return ret;
}
static int drm_platform_get_irq(struct drm_device *dev)
{
return platform_get_irq(dev->platformdev, 0);
}
static const char *drm_platform_get_name(struct drm_device *dev)
{
return dev->platformdev->name;
}
static int drm_platform_set_busid(struct drm_device *dev, struct drm_master *master)
{
int len, ret, id;
master->unique_len = 13 + strlen(dev->platformdev->name);
master->unique_size = master->unique_len;
master->unique = kmalloc(master->unique_len + 1, GFP_KERNEL);
if (master->unique == NULL)
return -ENOMEM;
id = dev->platformdev->id;
/* if only a single instance of the platform device, id will be
* set to -1.. use 0 instead to avoid a funny looking bus-id:
*/
if (id == -1)
id = 0;
len = snprintf(master->unique, master->unique_len,
"platform:%s:%02d", dev->platformdev->name, id);
if (len > master->unique_len) {
DRM_ERROR("Unique buffer overflowed\n");
ret = -EINVAL;
goto err;
}
dev->devname =
kmalloc(strlen(dev->platformdev->name) +
master->unique_len + 2, GFP_KERNEL);
if (dev->devname == NULL) {
ret = -ENOMEM;
goto err;
}
sprintf(dev->devname, "%s@%s", dev->platformdev->name,
master->unique);
return 0;
err:
return ret;
}
static struct drm_bus drm_platform_bus = {
.bus_type = DRIVER_BUS_PLATFORM,
.get_irq = drm_platform_get_irq,
.get_name = drm_platform_get_name,
.set_busid = drm_platform_set_busid,
};
/**
* Platform device initialization. Called direct from modules.
*
* \return zero on success or a negative number on failure.
*
* Initializes a drm_device structures,registering the
* stubs
*
* Expands the \c DRIVER_PREINIT and \c DRIVER_POST_INIT macros before and
* after the initialization for driver customization.
*/
int drm_platform_init(struct drm_driver *driver, struct platform_device *platform_device)
{
DRM_DEBUG("\n");
driver->kdriver.platform_device = platform_device;
driver->bus = &drm_platform_bus;
return drm_get_platform_dev(platform_device, driver);
}
EXPORT_SYMBOL(drm_platform_init);