Den 02.09.2018 22.56, skrev Sam Ravnborg:
Hi Noralf.
Only nitpicks, I have not the background
to review the actual implmentation.
So no tags from me to put on the commit.
Sam
+/**
+ * drm_gem_shmem_create - Allocate an object with the given size
+ * @dev: DRM device
+ * @size: Size of the object to allocate
+ *
+ * This function creates a shmem GEM object. The default cache mode is
+ * DRM_GEM_SHMEM_BO_CACHED. The &drm_driver->gem_create_object callback can be
+ * used override this.
used to override this.
^^
+ *
+ * Returns:
+ * A struct drm_gem_shmem_object * on success or an ERR_PTR()-encoded negative
+ * error code on failure.
+ */
+struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t size)
+{
+ struct drm_gem_shmem_object *shmem;
+ struct drm_gem_object *obj;
+ int ret;
+
+ size = PAGE_ALIGN(size);
+
+ if (dev->driver->gem_create_object)
+ obj = dev->driver->gem_create_object(dev, size);
+ else
+ obj = kzalloc(sizeof(*shmem), GFP_KERNEL);
+ if (!obj)
+ return ERR_PTR(-ENOMEM);
+
+ shmem = to_drm_gem_shmem_obj(obj);
+
+ if (!dev->driver->gem_create_object)
+ shmem->cache_mode = DRM_GEM_SHMEM_BO_CACHED;
+
+ ret = drm_gem_object_init(dev, obj, size);
+ if (ret)
+ goto err_free;
Some users of drm_gem_object_init() calls drm_gem_object_put_unlocked(obj)
when there is an error. Others call kfree() liek in this case.
I could also have done that if I initialized the mutexes earlier to match
up with the destroy in *_free_object. But it doesn't buy me anything,
so I prefer to stay with how the majority does it.
I really like to use Elixir when tracking down how drivers use the
various DRM functions:
https://elixir.bootlin.com/linux/latest/ident/drm_gem_object_init
+
+ ret = drm_gem_create_mmap_offset(obj);
+ if (ret)
+ goto err_release;
+
+ mutex_init(&shmem->pages_lock);
+ mutex_init(&shmem->vmap_lock);
+
+ return shmem;
+
+err_release:
+ drm_gem_object_release(obj);
+err_free:
+ kfree(shmem);
+
+ return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_create);
+
+
+static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem)
+{
+ struct drm_gem_object *obj = &shmem->base;
+ struct page **pages;
+
+ if (shmem->pages_use_count++ > 0)
+ return 0;
+
+ pages = drm_gem_get_pages(obj);
+ if (IS_ERR(pages)) {
+ DRM_DEBUG_KMS("Failed to get pages (%ld)\n", PTR_ERR(pages));
+ shmem->pages_use_count = 0;
+ return PTR_ERR(pages);
+ }
+
+ shmem->pages = pages;
+
+ return 0;
+}
+
+/*
+ * drm_gem_shmem_get_pages - Allocate backing pages for a shmem GEM object
+ * @shmem: shmem GEM object
+ *
+ * This function makes sure that backing pages exists for the shmem GEM object
+ * and increases the use count.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem)
+{
+ int ret;
+
+ ret = mutex_lock_interruptible(&shmem->pages_lock);
+ if (ret)
+ return ret;
+ ret = drm_gem_shmem_get_pages_locked(shmem);
+ mutex_unlock(&shmem->pages_lock);
+
+ return ret;
+}
+EXPORT_SYMBOL(drm_gem_shmem_get_pages);
+
The functions is named *_unlocked, but called with a lock held.
Inconsistent?
Indeed it is.
Thanks,
Noralf
+static void drm_gem_shmem_put_pages_unlocked(struct drm_gem_shmem_object *shmem)
+{
+ struct drm_gem_object *obj = &shmem->base;
+
+ if (WARN_ON_ONCE(!shmem->pages_use_count))
+ return;
+
+ if (--shmem->pages_use_count > 0)
+ return;
+
+ drm_gem_put_pages(obj, shmem->pages,
+ shmem->pages_mark_dirty_on_put,
+ shmem->pages_mark_accessed_on_put);
+ shmem->pages = NULL;
+}
+
+/*
+ * drm_gem_shmem_put_pages - Decrease use count on the backing pages for a shmem GEM object
+ * @shmem: shmem GEM object
+ *
+ * This function decreases the use count and puts the backing pages when use drops to zero.
+ */
+void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem)
+{
+ mutex_lock(&shmem->pages_lock);
+ drm_gem_shmem_put_pages_unlocked(shmem);
+ mutex_unlock(&shmem->pages_lock);
+}
+EXPORT_SYMBOL(drm_gem_shmem_put_pages);
+
+static int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem)
+{
+ struct drm_gem_object *obj = &shmem->base;
+ int ret;
+
+ if (shmem->vmap_use_count++ > 0)
+ return 0;
+
+ ret = drm_gem_shmem_get_pages(shmem);
+ if (ret)
+ goto err_zero_use;
+
+ if (obj->import_attach) {
+ shmem->vaddr = dma_buf_vmap(obj->import_attach->dmabuf);
+ } else {
+ pgprot_t prot;
+
+ switch (shmem->cache_mode) {
+ case DRM_GEM_SHMEM_BO_UNKNOWN:
No printout to help the coder that did not set this?
+ ret = -EINVAL;
+ goto err_put_pages;
+
+ case DRM_GEM_SHMEM_BO_WRITECOMBINED:
+ prot = pgprot_writecombine(PAGE_KERNEL);
+ break;
+
+ case DRM_GEM_SHMEM_BO_UNCACHED:
+ prot = pgprot_noncached(PAGE_KERNEL);
+ break;
+
+ case DRM_GEM_SHMEM_BO_CACHED:
+ prot = PAGE_KERNEL;
+ break;
+ }
+
+ shmem->vaddr = vmap(shmem->pages, obj->size >> PAGE_SHIFT, VM_MAP, prot);
+ }
+
+ if (!shmem->vaddr) {
+ DRM_DEBUG_KMS("Failed to vmap pages\n");
+ ret = -ENOMEM;
+ goto err_put_pages;
+ }
+
+ return 0;
+
+err_put_pages:
+ drm_gem_shmem_put_pages(shmem);
+err_zero_use:
+ shmem->vmap_use_count = 0;
+
+ return ret;
+}
+
+/*
+ * drm_gem_shmem_vmap - Create a virtual mapping for a shmem GEM object
+ * @shmem: shmem GEM object
+ *
+ * This function makes sure that a virtual address exists for the buffer backing
+ * the shmem GEM object.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_gem_shmem_vmap(struct drm_gem_shmem_object *shmem)
+{
+ int ret;
+
+ ret = mutex_lock_interruptible(&shmem->vmap_lock);
+ if (ret)
+ return ret;
+ ret = drm_gem_shmem_vmap_locked(shmem);
+ mutex_unlock(&shmem->vmap_lock);
+
+ return ret;
+}
+EXPORT_SYMBOL(drm_gem_shmem_vmap);
+
+static void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem)
+{
+ struct drm_gem_object *obj = &shmem->base;
+
+ if (WARN_ON_ONCE(!shmem->vmap_use_count))
+ return;
+
+ if (--shmem->vmap_use_count > 0)
+ return;
+
+ if (obj->import_attach)
+ dma_buf_vunmap(obj->import_attach->dmabuf, shmem->vaddr);
+ else
+ vunmap(shmem->vaddr);
+
+ shmem->vaddr = NULL;
+ drm_gem_shmem_put_pages(shmem);
+}
+
+/*
+ * drm_gem_shmem_vunmap - Unmap a virtual mapping fo a shmem GEM object
+ * @shmem: shmem GEM object
+ *
+ * This function removes the virtual address when use count drops to zero.
+ */
+void drm_gem_shmem_vunmap(struct drm_gem_shmem_object *shmem)
+{
+ mutex_lock(&shmem->vmap_lock);
+ drm_gem_shmem_vunmap_locked(shmem);
+ mutex_unlock(&shmem->vmap_lock);
+}
+EXPORT_SYMBOL(drm_gem_shmem_vunmap);
+
+static struct drm_gem_shmem_object *
+drm_gem_shmem_create_with_handle(struct drm_file *file_priv,
+ struct drm_device *dev, size_t size,
+ uint32_t *handle)
+{
+ struct drm_gem_shmem_object *shmem;
+ int ret;
+
+ shmem = drm_gem_shmem_create(dev, size);
+ if (IS_ERR(shmem))
+ return shmem;
+
+ /*
+ * Allocate an id of idr table where the obj is registered
+ * and handle has the id what user can see.
+ */
+ ret = drm_gem_handle_create(file_priv, &shmem->base, handle);
+ /* drop reference from allocate - handle holds it now. */
+ drm_gem_object_put_unlocked(&shmem->base);
+ if (ret)
+ return ERR_PTR(ret);
+
+ return shmem;
+}
+
+/**
+ * drm_gem_shmem_dumb_create - Create a dumb shmem buffer object
+ * @file: DRM file structure to create the dumb buffer for
+ * @dev: DRM device
+ * @args: IOCTL data
+ *
+ * This function computes the pitch of the dumb buffer and rounds it up to an
+ * integer number of bytes per pixel. Drivers for hardware that doesn't have
+ * any additional restrictions on the pitch can directly use this function as
+ * their &drm_driver.dumb_create callback.
+ *
+ * For hardware with additional restrictions, drivers can adjust the fields
+ * set up by userspace before calling into this function.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev,
+ struct drm_mode_create_dumb *args)
+{
+ u32 min_pitch = DIV_ROUND_UP(args->width * args->bpp, 8);
+ struct drm_gem_shmem_object *shmem;
+
+ if (!args->pitch || !args->size) {
+ args->pitch = min_pitch;
+ args->size = args->pitch * args->height;
+ } else {
+ /* ensure sane minimum values */
+ if (args->pitch < min_pitch)
+ args->pitch = min_pitch;
+ if (args->size < args->pitch * args->height)
+ args->size = args->pitch * args->height;
+ }
+
+ shmem = drm_gem_shmem_create_with_handle(file, dev, args->size, &args->handle);
+
+ return PTR_ERR_OR_ZERO(shmem);
+}
+EXPORT_SYMBOL_GPL(drm_gem_shmem_dumb_create);
+
+static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf)
+{
+ struct vm_area_struct *vma = vmf->vma;
+ struct drm_gem_object *obj = vma->vm_private_data;
+ struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
+ /* We don't use vmf->pgoff since that has the fake offset: */
+ pgoff_t pgoff = (vmf->address - vma->vm_start) >> PAGE_SHIFT;
+ loff_t num_pages = obj->size >> PAGE_SHIFT;
+ struct page *page;
+
+ if (pgoff > num_pages || WARN_ON_ONCE(!shmem->pages))
+ return VM_FAULT_SIGBUS;
+
+ page = shmem->pages[pgoff];
+
+ return vmf_insert_page(vma, vmf->address, page);
+}
+
+static void drm_gem_shmem_vm_close(struct vm_area_struct *vma)
+{
+ struct drm_gem_object *obj = vma->vm_private_data;
+ struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
+
+ drm_gem_shmem_put_pages(shmem);
+ drm_gem_vm_close(vma);
+}
+
+const struct vm_operations_struct drm_gem_shmem_vm_ops = {
+ .fault = drm_gem_shmem_fault,
+ .open = drm_gem_vm_open,
+ .close = drm_gem_shmem_vm_close,
+};
+EXPORT_SYMBOL_GPL(drm_gem_shmem_vm_ops);
+
+static int drm_gem_shmem_mmap_obj(struct drm_gem_shmem_object *shmem,
+ struct vm_area_struct *vma)
+{
+ int ret;
+
+ ret = drm_gem_shmem_get_pages(shmem);
+ if (ret)
+ goto err_close;
+
+ /* VM_PFNMAP was set by drm_gem_mmap() */
+ vma->vm_flags &= ~VM_PFNMAP;
+ vma->vm_flags |= VM_MIXEDMAP;
+
+ switch (shmem->cache_mode) {
+ case DRM_GEM_SHMEM_BO_UNKNOWN:
+ ret = -EINVAL;
Print to help the programmer?
+ goto err_put_pages;
+
+ case DRM_GEM_SHMEM_BO_WRITECOMBINED:
+ vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
+ break;
+
+ case DRM_GEM_SHMEM_BO_UNCACHED:
+ vma->vm_page_prot = pgprot_noncached(vm_get_page_prot(vma->vm_flags));
+ break;
+
+ case DRM_GEM_SHMEM_BO_CACHED:
+ /*
+ * Shunt off cached objs to shmem file so they have their own
+ * address_space (so unmap_mapping_range does what we want,
+ * in particular in the case of mmap'd dmabufs)
+ */
+ fput(vma->vm_file);
+ get_file(shmem->base.filp);
+ vma->vm_pgoff = 0;
+ vma->vm_file = shmem->base.filp;
+ vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
+ break;
+ }
+
+ return 0;
+
+err_put_pages:
+ drm_gem_shmem_put_pages(shmem);
+err_close:
+ drm_gem_vm_close(vma);
+
+ return ret;
+}
+
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