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Commit 225b4590 authored by Bruno Prémont's avatar Bruno Prémont Committed by Jiri Kosina
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HID: picolcd: implement refcounting of framebuffer 



As our device may be hot-unplugged and framebuffer cannot handle
this case by itself we need to keep track of usage count so as
to release fb_info and framebuffer memory only after the last user
has closed framebuffer.

We need to do the freeing in a scheduled work as fb_release()
is called with fb_info lock held.

Signed-off-by: default avatarBruno Prémont <bonbons@linux-vserver.org>
Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
parent 365f1fcd

drivers/hid/hid-picolcd.c

+103 −7
Original line number Diff line number Diff line
@@ -439,6 +439,9 @@ static void picolcd_fb_update(struct picolcd_data *data) 
	int chip, tile, n;

	unsigned long flags;



	if (!data)

		return;



	spin_lock_irqsave(&data->lock, flags);

	if (!(data->status & PICOLCD_READY_FB)) {

		spin_unlock_irqrestore(&data->lock, flags);
@@ -461,6 +464,8 @@ static void picolcd_fb_update(struct picolcd_data *data) 
					data->fb_bitmap, data->fb_bpp, chip, tile) ||

				data->fb_force) {

				n += 2;

				if (!data->fb_info->par)

					return; /* device lost! */

				if (n >= HID_OUTPUT_FIFO_SIZE / 2) {

					usbhid_wait_io(data->hdev);

					n = 0;
@@ -531,11 +536,23 @@ static int picolcd_fb_blank(int blank, struct fb_info *info) 
static void picolcd_fb_destroy(struct fb_info *info)

{

	struct picolcd_data *data = info->par;

	u32 *ref_cnt = info->pseudo_palette;

	int may_release;



	info->par = NULL;

	if (data)

		data->fb_info = NULL;

	fb_deferred_io_cleanup(info);



	ref_cnt--;

	mutex_lock(&info->lock);

	(*ref_cnt)--;

	may_release = !ref_cnt;

	mutex_unlock(&info->lock);

	if (may_release) {

		framebuffer_release(info);

		vfree((u8 *)info->fix.smem_start);

	}

}



static int picolcd_fb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
@@ -564,6 +581,8 @@ static int picolcd_set_par(struct fb_info *info) 
{

	struct picolcd_data *data = info->par;

	u8 *tmp_fb, *o_fb;

	if (!data)

		return -ENODEV;

	if (info->var.bits_per_pixel == data->fb_bpp)

		return 0;

	/* switch between 1/8 bit depths */
@@ -603,10 +622,77 @@ static int picolcd_set_par(struct fb_info *info) 
	return 0;

}



/* Do refcounting on our FB and cleanup per worker if FB is

 * closed after unplug of our device

 * (fb_release holds info->lock and still touches info after

 *  we return so we can't release it immediately.

 */

struct picolcd_fb_cleanup_item {

	struct fb_info *info;

	struct picolcd_fb_cleanup_item *next;

};

static struct picolcd_fb_cleanup_item *fb_pending;

DEFINE_SPINLOCK(fb_pending_lock);



static void picolcd_fb_do_cleanup(struct work_struct *data)

{

	struct picolcd_fb_cleanup_item *item;

	unsigned long flags;



	do {

		spin_lock_irqsave(&fb_pending_lock, flags);

		item = fb_pending;

		fb_pending = item ? item->next : NULL;

		spin_unlock_irqrestore(&fb_pending_lock, flags);



		if (item) {

			u8 *fb = (u8 *)item->info->fix.smem_start;

			/* make sure we do not race against fb core when

			 * releasing */

			mutex_lock(&item->info->lock);

			mutex_unlock(&item->info->lock);

			framebuffer_release(item->info);

			vfree(fb);

		}

	} while (item);

}



DECLARE_WORK(picolcd_fb_cleanup, picolcd_fb_do_cleanup);



static int picolcd_fb_open(struct fb_info *info, int u)

{

	u32 *ref_cnt = info->pseudo_palette;

	ref_cnt--;



	(*ref_cnt)++;

	return 0;

}



static int picolcd_fb_release(struct fb_info *info, int u)

{

	u32 *ref_cnt = info->pseudo_palette;

	ref_cnt--;



	(*ref_cnt)++;

	if (!*ref_cnt) {

		unsigned long flags;

		struct picolcd_fb_cleanup_item *item = (struct picolcd_fb_cleanup_item *)ref_cnt;

		item--;

		spin_lock_irqsave(&fb_pending_lock, flags);

		item->next = fb_pending;

		fb_pending = item;

		spin_unlock_irqrestore(&fb_pending_lock, flags);

		schedule_work(&picolcd_fb_cleanup);

	}

	return 0;

}



/* Note this can't be const because of struct fb_info definition */

static struct fb_ops picolcdfb_ops = {

	.owner        = THIS_MODULE,

	.fb_destroy   = picolcd_fb_destroy,

	.fb_open      = picolcd_fb_open,

	.fb_release   = picolcd_fb_release,

	.fb_read      = fb_sys_read,

	.fb_write     = picolcd_fb_write,

	.fb_blank     = picolcd_fb_blank,
@@ -708,13 +794,13 @@ static int picolcd_init_framebuffer(struct picolcd_data *data) 
	 * - u32 for ref_count

	 * - 256*u32 for pseudo_palette

	 */

	info = framebuffer_alloc(257 * sizeof(u32), dev);

	info = framebuffer_alloc(257 * sizeof(u32) + sizeof(struct picolcd_fb_cleanup_item), dev);

	if (info == NULL) {

		dev_err(dev, "failed to allocate a framebuffer\n");

		goto err_nomem;

	}



	palette  = info->par;

	palette  = info->par + sizeof(struct picolcd_fb_cleanup_item);

	*palette = 1;

	palette++;

	for (i = 0; i < 256; i++)
@@ -775,18 +861,17 @@ static void picolcd_exit_framebuffer(struct picolcd_data *data) 
{

	struct fb_info *info = data->fb_info;

	u8 *fb_vbitmap = data->fb_vbitmap;

	u8 *fb_bitmap  = data->fb_bitmap;



	if (!info)

		return;



	info->par = NULL;

	device_remove_file(&data->hdev->dev, &dev_attr_fb_update_rate);

	unregister_framebuffer(info);

	data->fb_vbitmap = NULL;

	data->fb_bitmap  = NULL;

	data->fb_bpp     = 0;

	data->fb_info    = NULL;

	device_remove_file(&data->hdev->dev, &dev_attr_fb_update_rate);

	unregister_framebuffer(info);

	vfree(fb_bitmap);

	kfree(fb_vbitmap);

}
@@ -2603,6 +2688,13 @@ static void picolcd_remove(struct hid_device *hdev) 
	spin_lock_irqsave(&data->lock, flags);

	data->status |= PICOLCD_FAILED;

	spin_unlock_irqrestore(&data->lock, flags);

#ifdef CONFIG_HID_PICOLCD_FB

	/* short-circuit FB as early as possible in order to

	 * avoid long delays if we host console.

	 */

	if (data->fb_info)

		data->fb_info->par = NULL;

#endif



	picolcd_exit_devfs(data);

	device_remove_file(&hdev->dev, &dev_attr_operation_mode);
@@ -2660,6 +2752,10 @@ static int __init picolcd_init(void) 
static void __exit picolcd_exit(void)

{

	hid_unregister_driver(&picolcd_driver);

#ifdef CONFIG_HID_PICOLCD_FB

	flush_scheduled_work();

	WARN_ON(fb_pending);

#endif

}



module_init(picolcd_init);