fbdev: mm: Deferred IO support
This implements deferred IO support in fbdev. Deferred IO is a way to delay
and repurpose IO. This implementation is done using mm's page_mkwrite and
page_mkclean hooks in order to detect, delay and then rewrite IO. This
functionality is used by hecubafb.
[adaplas]
This is useful for graphics hardware with no directly addressable/mappable
framebuffer. Implementing this will allow the "framebuffer" to be accesible
from user space via mmap().
Signed-off-by: Jaya Kumar <jayakumar.lkml@gmail.com>
Signed-off-by: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
index 8dfa88a..61c0a03 100644
--- a/drivers/video/Kconfig
+++ b/drivers/video/Kconfig
@@ -91,6 +91,11 @@
blitting. This is used by drivers that don't provide their own
(accelerated) version.
+config FB_DEFERRED_IO
+ bool
+ depends on FB
+ default y
+
config FB_SVGALIB
tristate
depends on FB
diff --git a/drivers/video/Makefile b/drivers/video/Makefile
index 2814624..deb5fa5 100644
--- a/drivers/video/Makefile
+++ b/drivers/video/Makefile
@@ -20,6 +20,7 @@
obj-$(CONFIG_FB_SVGALIB) += svgalib.o
obj-$(CONFIG_FB_MACMODES) += macmodes.o
obj-$(CONFIG_FB_DDC) += fb_ddc.o
+obj-$(CONFIG_FB_DEFERRED_IO) += fb_defio.o
# Hardware specific drivers go first
obj-$(CONFIG_FB_AMIGA) += amifb.o c2p.o
diff --git a/drivers/video/fb_defio.c b/drivers/video/fb_defio.c
new file mode 100644
index 0000000..cc780f4
--- /dev/null
+++ b/drivers/video/fb_defio.c
@@ -0,0 +1,137 @@
+/*
+ * linux/drivers/video/fb_defio.c
+ *
+ * Copyright (C) 2006 Jaya Kumar
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file COPYING in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/fb.h>
+#include <linux/list.h>
+#include <asm/uaccess.h>
+
+/* to support deferred IO */
+#include <linux/rmap.h>
+#include <linux/pagemap.h>
+
+/* this is to find and return the vmalloc-ed fb pages */
+static struct page* fb_deferred_io_nopage(struct vm_area_struct *vma,
+ unsigned long vaddr, int *type)
+{
+ unsigned long offset;
+ struct page *page;
+ struct fb_info *info = vma->vm_private_data;
+
+ offset = (vaddr - vma->vm_start) + (vma->vm_pgoff << PAGE_SHIFT);
+ if (offset >= info->fix.smem_len)
+ return NOPAGE_SIGBUS;
+
+ page = vmalloc_to_page(info->screen_base + offset);
+ if (!page)
+ return NOPAGE_OOM;
+
+ get_page(page);
+ if (type)
+ *type = VM_FAULT_MINOR;
+ return page;
+}
+
+/* vm_ops->page_mkwrite handler */
+int fb_deferred_io_mkwrite(struct vm_area_struct *vma,
+ struct page *page)
+{
+ struct fb_info *info = vma->vm_private_data;
+ struct fb_deferred_io *fbdefio = info->fbdefio;
+
+ /* this is a callback we get when userspace first tries to
+ write to the page. we schedule a workqueue. that workqueue
+ will eventually mkclean the touched pages and execute the
+ deferred framebuffer IO. then if userspace touches a page
+ again, we repeat the same scheme */
+
+ /* protect against the workqueue changing the page list */
+ mutex_lock(&fbdefio->lock);
+ list_add(&page->lru, &fbdefio->pagelist);
+ mutex_unlock(&fbdefio->lock);
+
+ /* come back after delay to process the deferred IO */
+ schedule_delayed_work(&info->deferred_work, fbdefio->delay);
+ return 0;
+}
+
+static struct vm_operations_struct fb_deferred_io_vm_ops = {
+ .nopage = fb_deferred_io_nopage,
+ .page_mkwrite = fb_deferred_io_mkwrite,
+};
+
+static int fb_deferred_io_mmap(struct fb_info *info, struct vm_area_struct *vma)
+{
+ vma->vm_ops = &fb_deferred_io_vm_ops;
+ vma->vm_flags |= ( VM_IO | VM_RESERVED | VM_DONTEXPAND );
+ vma->vm_private_data = info;
+ return 0;
+}
+
+/* workqueue callback */
+static void fb_deferred_io_work(struct work_struct *work)
+{
+ struct fb_info *info = container_of(work, struct fb_info,
+ deferred_work.work);
+ struct list_head *node, *next;
+ struct page *cur;
+ struct fb_deferred_io *fbdefio = info->fbdefio;
+
+ /* here we mkclean the pages, then do all deferred IO */
+ mutex_lock(&fbdefio->lock);
+ list_for_each_entry(cur, &fbdefio->pagelist, lru) {
+ lock_page(cur);
+ page_mkclean(cur);
+ unlock_page(cur);
+ }
+
+ /* driver's callback with pagelist */
+ fbdefio->deferred_io(info, &fbdefio->pagelist);
+
+ /* clear the list */
+ list_for_each_safe(node, next, &fbdefio->pagelist) {
+ list_del(node);
+ }
+ mutex_unlock(&fbdefio->lock);
+}
+
+void fb_deferred_io_init(struct fb_info *info)
+{
+ struct fb_deferred_io *fbdefio = info->fbdefio;
+
+ BUG_ON(!fbdefio);
+ mutex_init(&fbdefio->lock);
+ info->fbops->fb_mmap = fb_deferred_io_mmap;
+ INIT_DELAYED_WORK(&info->deferred_work, fb_deferred_io_work);
+ INIT_LIST_HEAD(&fbdefio->pagelist);
+ if (fbdefio->delay == 0) /* set a default of 1 s */
+ fbdefio->delay = HZ;
+}
+EXPORT_SYMBOL_GPL(fb_deferred_io_init);
+
+void fb_deferred_io_cleanup(struct fb_info *info)
+{
+ struct fb_deferred_io *fbdefio = info->fbdefio;
+
+ BUG_ON(!fbdefio);
+ cancel_delayed_work(&info->deferred_work);
+ flush_scheduled_work();
+}
+EXPORT_SYMBOL_GPL(fb_deferred_io_cleanup);
+
+MODULE_LICENSE("GPL");