drivers/video/fb_defio.c

   1 /*
   2  *  linux/drivers/video/fb_defio.c
   3  *
   4  *  Copyright (C) 2006 Jaya Kumar
   5  *
   6  * This file is subject to the terms and conditions of the GNU General Public
   7  * License. See the file COPYING in the main directory of this archive
   8  * for more details.
   9  */
  10
  11 #include <linux/module.h>
  12 #include <linux/kernel.h>
  13 #include <linux/errno.h>
  14 #include <linux/string.h>
  15 #include <linux/mm.h>
  16 #include <linux/slab.h>
  17 #include <linux/vmalloc.h>
  18 #include <linux/delay.h>
  19 #include <linux/interrupt.h>
  20 #include <linux/fb.h>
  21 #include <linux/list.h>
  22
  23 /* to support deferred IO */
  24 #include <linux/rmap.h>
  25 #include <linux/pagemap.h>
  26
  27 /* this is to find and return the vmalloc-ed fb pages */
  28 static int fb_deferred_io_fault(struct vm_area_struct *vma,
  29                                 struct vm_fault *vmf)
  30 {
  31         unsigned long offset;
  32         struct page *page;
  33         struct fb_info *info = vma->vm_private_data;
  34         /* info->screen_base is virtual memory */
  35         void *screen_base = (void __force *) info->screen_base;
  36
  37         offset = vmf->pgoff << PAGE_SHIFT;
  38         if (offset >= info->fix.smem_len)
  39                 return VM_FAULT_SIGBUS;
  40
  41         page = vmalloc_to_page(screen_base + offset);
  42         if (!page)
  43                 return VM_FAULT_SIGBUS;
  44
  45         get_page(page);
  46
  47         if (vma->vm_file)
  48                 page->mapping = vma->vm_file->f_mapping;
  49         else
  50                 printk(KERN_ERR "no mapping available\n");
  51
  52         BUG_ON(!page->mapping);
  53         page->index = vmf->pgoff;
  54
  55         vmf->page = page;
  56         return 0;
  57 }
  58
  59 int fb_deferred_io_fsync(struct file *file, struct dentry *dentry, int datasync)
  60 {
  61         struct fb_info *info = file->private_data;
  62
  63         /* Kill off the delayed work */
  64         cancel_rearming_delayed_work(&info->deferred_work);
  65
  66         /* Run it immediately */
  67         return schedule_delayed_work(&info->deferred_work, 0);
  68 }
  69 EXPORT_SYMBOL_GPL(fb_deferred_io_fsync);
  70
  71 /* vm_ops->page_mkwrite handler */
  72 static int fb_deferred_io_mkwrite(struct vm_area_struct *vma,
  73                                   struct page *page)
  74 {
  75         struct fb_info *info = vma->vm_private_data;
  76         struct fb_deferred_io *fbdefio = info->fbdefio;
  77         struct page *cur;
  78
  79         /* this is a callback we get when userspace first tries to
  80         write to the page. we schedule a workqueue. that workqueue
  81         will eventually mkclean the touched pages and execute the
  82         deferred framebuffer IO. then if userspace touches a page
  83         again, we repeat the same scheme */
  84
  85         /* protect against the workqueue changing the page list */
  86         mutex_lock(&fbdefio->lock);
  87
  88         /* we loop through the pagelist before adding in order
  89         to keep the pagelist sorted */
  90         list_for_each_entry(cur, &fbdefio->pagelist, lru) {
  91                 /* this check is to catch the case where a new
  92                 process could start writing to the same page
  93                 through a new pte. this new access can cause the
  94                 mkwrite even when the original ps's pte is marked
  95                 writable */
  96                 if (unlikely(cur == page))
  97                         goto page_already_added;
  98                 else if (cur->index > page->index)
  99                         break;
 100         }
 101
 102         list_add_tail(&page->lru, &cur->lru);
 103
 104 page_already_added:
 105         mutex_unlock(&fbdefio->lock);
 106
 107         /* come back after delay to process the deferred IO */
 108         schedule_delayed_work(&info->deferred_work, fbdefio->delay);
 109         return 0;
 110 }
 111
 112 static struct vm_operations_struct fb_deferred_io_vm_ops = {
 113         .fault          = fb_deferred_io_fault,
 114         .page_mkwrite   = fb_deferred_io_mkwrite,
 115 };
 116
 117 static int fb_deferred_io_mmap(struct fb_info *info, struct vm_area_struct *vma)
 118 {
 119         vma->vm_ops = &fb_deferred_io_vm_ops;
 120         vma->vm_flags |= ( VM_IO | VM_RESERVED | VM_DONTEXPAND );
 121         vma->vm_private_data = info;
 122         return 0;
 123 }
 124
 125 /* workqueue callback */
 126 static void fb_deferred_io_work(struct work_struct *work)
 127 {
 128         struct fb_info *info = container_of(work, struct fb_info,
 129                                                 deferred_work.work);
 130         struct list_head *node, *next;
 131         struct page *cur;
 132         struct fb_deferred_io *fbdefio = info->fbdefio;
 133
 134         /* here we mkclean the pages, then do all deferred IO */
 135         mutex_lock(&fbdefio->lock);
 136         list_for_each_entry(cur, &fbdefio->pagelist, lru) {
 137                 lock_page(cur);
 138                 page_mkclean(cur);
 139                 unlock_page(cur);
 140         }
 141
 142         /* driver's callback with pagelist */
 143         fbdefio->deferred_io(info, &fbdefio->pagelist);
 144
 145         /* clear the list */
 146         list_for_each_safe(node, next, &fbdefio->pagelist) {
 147                 list_del(node);
 148         }
 149         mutex_unlock(&fbdefio->lock);
 150 }
 151
 152 void fb_deferred_io_init(struct fb_info *info)
 153 {
 154         struct fb_deferred_io *fbdefio = info->fbdefio;
 155
 156         BUG_ON(!fbdefio);
 157         mutex_init(&fbdefio->lock);
 158         info->fbops->fb_mmap = fb_deferred_io_mmap;
 159         INIT_DELAYED_WORK(&info->deferred_work, fb_deferred_io_work);
 160         INIT_LIST_HEAD(&fbdefio->pagelist);
 161         if (fbdefio->delay == 0) /* set a default of 1 s */
 162                 fbdefio->delay = HZ;
 163 }
 164 EXPORT_SYMBOL_GPL(fb_deferred_io_init);
 165
 166 void fb_deferred_io_cleanup(struct fb_info *info)
 167 {
 168         void *screen_base = (void __force *) info->screen_base;
 169         struct fb_deferred_io *fbdefio = info->fbdefio;
 170         struct page *page;
 171         int i;
 172
 173         BUG_ON(!fbdefio);
 174         cancel_delayed_work(&info->deferred_work);
 175         flush_scheduled_work();
 176
 177         /* clear out the mapping that we setup */
 178         for (i = 0 ; i < info->fix.smem_len; i += PAGE_SIZE) {
 179                 page = vmalloc_to_page(screen_base + i);
 180                 page->mapping = NULL;
 181         }
 182 }
 183 EXPORT_SYMBOL_GPL(fb_deferred_io_cleanup);
 184
 185 MODULE_LICENSE("GPL");