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 struct page *fb_deferred_io_page(struct fb_info *info, unsigned long offs)
  28 {
  29         void *screen_base = (void __force *) info->screen_base;
  30         struct page *page;
  31
  32         if (is_vmalloc_addr(screen_base + offs))
  33                 page = vmalloc_to_page(screen_base + offs);
  34         else
  35                 page = pfn_to_page((info->fix.smem_start + offs) >> PAGE_SHIFT);
  36
  37         return page;
  38 }
  39
  40 /* this is to find and return the vmalloc-ed fb pages */
  41 static int fb_deferred_io_fault(struct vm_area_struct *vma,
  42                                 struct vm_fault *vmf)
  43 {
  44         unsigned long offset;
  45         struct page *page;
  46         struct fb_info *info = vma->vm_private_data;
  47
  48         offset = vmf->pgoff << PAGE_SHIFT;
  49         if (offset >= info->fix.smem_len)
  50                 return VM_FAULT_SIGBUS;
  51
  52         page = fb_deferred_io_page(info, offset);
  53         if (!page)
  54                 return VM_FAULT_SIGBUS;
  55
  56         get_page(page);
  57
  58         if (vma->vm_file)
  59                 page->mapping = vma->vm_file->f_mapping;
  60         else
  61                 printk(KERN_ERR "no mapping available\n");
  62
  63         BUG_ON(!page->mapping);
  64         page->index = vmf->pgoff;
  65
  66         vmf->page = page;
  67         return 0;
  68 }
  69
  70 int fb_deferred_io_fsync(struct file *file, struct dentry *dentry, int datasync)
  71 {
  72         struct fb_info *info = file->private_data;
  73
  74         /* Skip if deferred io is complied-in but disabled on this fbdev */
  75         if (!info->fbdefio)
  76                 return 0;
  77
  78         /* Kill off the delayed work */
  79         cancel_rearming_delayed_work(&info->deferred_work);
  80
  81         /* Run it immediately */
  82         return schedule_delayed_work(&info->deferred_work, 0);
  83 }
  84 EXPORT_SYMBOL_GPL(fb_deferred_io_fsync);
  85
  86 /* vm_ops->page_mkwrite handler */
  87 static int fb_deferred_io_mkwrite(struct vm_area_struct *vma,
  88                                   struct vm_fault *vmf)
  89 {
  90         struct page *page = vmf->page;
  91         struct fb_info *info = vma->vm_private_data;
  92         struct fb_deferred_io *fbdefio = info->fbdefio;
  93         struct page *cur;
  94
  95         /* this is a callback we get when userspace first tries to
  96         write to the page. we schedule a workqueue. that workqueue
  97         will eventually mkclean the touched pages and execute the
  98         deferred framebuffer IO. then if userspace touches a page
  99         again, we repeat the same scheme */
 100
 101         /* protect against the workqueue changing the page list */
 102         mutex_lock(&fbdefio->lock);
 103
 104         /* we loop through the pagelist before adding in order
 105         to keep the pagelist sorted */
 106         list_for_each_entry(cur, &fbdefio->pagelist, lru) {
 107                 /* this check is to catch the case where a new
 108                 process could start writing to the same page
 109                 through a new pte. this new access can cause the
 110                 mkwrite even when the original ps's pte is marked
 111                 writable */
 112                 if (unlikely(cur == page))
 113                         goto page_already_added;
 114                 else if (cur->index > page->index)
 115                         break;
 116         }
 117
 118         list_add_tail(&page->lru, &cur->lru);
 119
 120 page_already_added:
 121         mutex_unlock(&fbdefio->lock);
 122
 123         /* come back after delay to process the deferred IO */
 124         schedule_delayed_work(&info->deferred_work, fbdefio->delay);
 125         return 0;
 126 }
 127
 128 static struct vm_operations_struct fb_deferred_io_vm_ops = {
 129         .fault          = fb_deferred_io_fault,
 130         .page_mkwrite   = fb_deferred_io_mkwrite,
 131 };
 132
 133 static int fb_deferred_io_set_page_dirty(struct page *page)
 134 {
 135         if (!PageDirty(page))
 136                 SetPageDirty(page);
 137         return 0;
 138 }
 139
 140 static const struct address_space_operations fb_deferred_io_aops = {
 141         .set_page_dirty = fb_deferred_io_set_page_dirty,
 142 };
 143
 144 static int fb_deferred_io_mmap(struct fb_info *info, struct vm_area_struct *vma)
 145 {
 146         vma->vm_ops = &fb_deferred_io_vm_ops;
 147         vma->vm_flags |= ( VM_IO | VM_RESERVED | VM_DONTEXPAND );
 148         vma->vm_private_data = info;
 149         return 0;
 150 }
 151
 152 /* workqueue callback */
 153 static void fb_deferred_io_work(struct work_struct *work)
 154 {
 155         struct fb_info *info = container_of(work, struct fb_info,
 156                                                 deferred_work.work);
 157         struct list_head *node, *next;
 158         struct page *cur;
 159         struct fb_deferred_io *fbdefio = info->fbdefio;
 160
 161         /* here we mkclean the pages, then do all deferred IO */
 162         mutex_lock(&fbdefio->lock);
 163         list_for_each_entry(cur, &fbdefio->pagelist, lru) {
 164                 lock_page(cur);
 165                 page_mkclean(cur);
 166                 unlock_page(cur);
 167         }
 168
 169         /* driver's callback with pagelist */
 170         fbdefio->deferred_io(info, &fbdefio->pagelist);
 171
 172         /* clear the list */
 173         list_for_each_safe(node, next, &fbdefio->pagelist) {
 174                 list_del(node);
 175         }
 176         mutex_unlock(&fbdefio->lock);
 177 }
 178
 179 void fb_deferred_io_init(struct fb_info *info)
 180 {
 181         struct fb_deferred_io *fbdefio = info->fbdefio;
 182
 183         BUG_ON(!fbdefio);
 184         mutex_init(&fbdefio->lock);
 185         info->fbops->fb_mmap = fb_deferred_io_mmap;
 186         INIT_DELAYED_WORK(&info->deferred_work, fb_deferred_io_work);
 187         INIT_LIST_HEAD(&fbdefio->pagelist);
 188         if (fbdefio->delay == 0) /* set a default of 1 s */
 189                 fbdefio->delay = HZ;
 190 }
 191 EXPORT_SYMBOL_GPL(fb_deferred_io_init);
 192
 193 void fb_deferred_io_open(struct fb_info *info,
 194                          struct inode *inode,
 195                          struct file *file)
 196 {
 197         file->f_mapping->a_ops = &fb_deferred_io_aops;
 198 }
 199 EXPORT_SYMBOL_GPL(fb_deferred_io_open);
 200
 201 void fb_deferred_io_cleanup(struct fb_info *info)
 202 {
 203         struct fb_deferred_io *fbdefio = info->fbdefio;
 204         struct page *page;
 205         int i;
 206
 207         BUG_ON(!fbdefio);
 208         cancel_delayed_work(&info->deferred_work);
 209         flush_scheduled_work();
 210
 211         /* clear out the mapping that we setup */
 212         for (i = 0 ; i < info->fix.smem_len; i += PAGE_SIZE) {
 213                 page = fb_deferred_io_page(info, i);
 214                 page->mapping = NULL;
 215         }
 216
 217         info->fbops->fb_mmap = NULL;
 218         mutex_destroy(&fbdefio->lock);
 219 }
 220 EXPORT_SYMBOL_GPL(fb_deferred_io_cleanup);
 221
 222 MODULE_LICENSE("GPL");