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         /* Skip if deferred io is complied-in but disabled on this fbdev */
  64         if (!info->fbdefio)
  65                 return 0;
  66
  67         /* Kill off the delayed work */
  68         cancel_rearming_delayed_work(&info->deferred_work);
  69
  70         /* Run it immediately */
  71         return schedule_delayed_work(&info->deferred_work, 0);
  72 }
  73 EXPORT_SYMBOL_GPL(fb_deferred_io_fsync);
  74
  75 /* vm_ops->page_mkwrite handler */
  76 static int fb_deferred_io_mkwrite(struct vm_area_struct *vma,
  77                                   struct page *page)
  78 {
  79         struct fb_info *info = vma->vm_private_data;
  80         struct fb_deferred_io *fbdefio = info->fbdefio;
  81         struct page *cur;
  82
  83         /* this is a callback we get when userspace first tries to
  84         write to the page. we schedule a workqueue. that workqueue
  85         will eventually mkclean the touched pages and execute the
  86         deferred framebuffer IO. then if userspace touches a page
  87         again, we repeat the same scheme */
  88
  89         /* protect against the workqueue changing the page list */
  90         mutex_lock(&fbdefio->lock);
  91
  92         /* we loop through the pagelist before adding in order
  93         to keep the pagelist sorted */
  94         list_for_each_entry(cur, &fbdefio->pagelist, lru) {
  95                 /* this check is to catch the case where a new
  96                 process could start writing to the same page
  97                 through a new pte. this new access can cause the
  98                 mkwrite even when the original ps's pte is marked
  99                 writable */
 100                 if (unlikely(cur == page))
 101                         goto page_already_added;
 102                 else if (cur->index > page->index)
 103                         break;
 104         }
 105
 106         list_add_tail(&page->lru, &cur->lru);
 107
 108 page_already_added:
 109         mutex_unlock(&fbdefio->lock);
 110
 111         /* come back after delay to process the deferred IO */
 112         schedule_delayed_work(&info->deferred_work, fbdefio->delay);
 113         return 0;
 114 }
 115
 116 static struct vm_operations_struct fb_deferred_io_vm_ops = {
 117         .fault          = fb_deferred_io_fault,
 118         .page_mkwrite   = fb_deferred_io_mkwrite,
 119 };
 120
 121 static int fb_deferred_io_set_page_dirty(struct page *page)
 122 {
 123         if (!PageDirty(page))
 124                 SetPageDirty(page);
 125         return 0;
 126 }
 127
 128 static const struct address_space_operations fb_deferred_io_aops = {
 129         .set_page_dirty = fb_deferred_io_set_page_dirty,
 130 };
 131
 132 static int fb_deferred_io_mmap(struct fb_info *info, struct vm_area_struct *vma)
 133 {
 134         vma->vm_ops = &fb_deferred_io_vm_ops;
 135         vma->vm_flags |= ( VM_IO | VM_RESERVED | VM_DONTEXPAND );
 136         vma->vm_private_data = info;
 137         return 0;
 138 }
 139
 140 /* workqueue callback */
 141 static void fb_deferred_io_work(struct work_struct *work)
 142 {
 143         struct fb_info *info = container_of(work, struct fb_info,
 144                                                 deferred_work.work);
 145         struct list_head *node, *next;
 146         struct page *cur;
 147         struct fb_deferred_io *fbdefio = info->fbdefio;
 148
 149         /* here we mkclean the pages, then do all deferred IO */
 150         mutex_lock(&fbdefio->lock);
 151         list_for_each_entry(cur, &fbdefio->pagelist, lru) {
 152                 lock_page(cur);
 153                 page_mkclean(cur);
 154                 unlock_page(cur);
 155         }
 156
 157         /* driver's callback with pagelist */
 158         fbdefio->deferred_io(info, &fbdefio->pagelist);
 159
 160         /* clear the list */
 161         list_for_each_safe(node, next, &fbdefio->pagelist) {
 162                 list_del(node);
 163         }
 164         mutex_unlock(&fbdefio->lock);
 165 }
 166
 167 void fb_deferred_io_init(struct fb_info *info)
 168 {
 169         struct fb_deferred_io *fbdefio = info->fbdefio;
 170
 171         BUG_ON(!fbdefio);
 172         mutex_init(&fbdefio->lock);
 173         info->fbops->fb_mmap = fb_deferred_io_mmap;
 174         INIT_DELAYED_WORK(&info->deferred_work, fb_deferred_io_work);
 175         INIT_LIST_HEAD(&fbdefio->pagelist);
 176         if (fbdefio->delay == 0) /* set a default of 1 s */
 177                 fbdefio->delay = HZ;
 178 }
 179 EXPORT_SYMBOL_GPL(fb_deferred_io_init);
 180
 181 void fb_deferred_io_open(struct fb_info *info,
 182                          struct inode *inode,
 183                          struct file *file)
 184 {
 185         file->f_mapping->a_ops = &fb_deferred_io_aops;
 186 }
 187 EXPORT_SYMBOL_GPL(fb_deferred_io_open);
 188
 189 void fb_deferred_io_cleanup(struct fb_info *info)
 190 {
 191         void *screen_base = (void __force *) info->screen_base;
 192         struct fb_deferred_io *fbdefio = info->fbdefio;
 193         struct page *page;
 194         int i;
 195
 196         BUG_ON(!fbdefio);
 197         cancel_delayed_work(&info->deferred_work);
 198         flush_scheduled_work();
 199
 200         /* clear out the mapping that we setup */
 201         for (i = 0 ; i < info->fix.smem_len; i += PAGE_SIZE) {
 202                 page = vmalloc_to_page(screen_base + i);
 203                 page->mapping = NULL;
 204         }
 205
 206         info->fbops->fb_mmap = NULL;
 207         mutex_destroy(&fbdefio->lock);
 208 }
 209 EXPORT_SYMBOL_GPL(fb_deferred_io_cleanup);
 210
 211 MODULE_LICENSE("GPL");