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Commit 3c21cfc4 authored by Daniel Drake's avatar Daniel Drake Committed by Stefan Richter
Browse files

video1394: small optimizations to frame retrieval codepath 



Add some GCC branch prediction optimizations to unlikely error/safety
conditions in the ioctl handling code commonly called during an application's
capture loop.

Signed-off-by: default avatarDaniel Drake <ddrake@brontes3d.com>
Signed-off-by: default avatarStefan Richter <stefanr@s5r6.in-berlin.de>
parent c1c9c7cd

drivers/ieee1394/video1394.c

+10 −8
Original line number Diff line number Diff line
@@ -884,13 +884,14 @@ static int __video1394_ioctl(struct file *file, 
		struct dma_iso_ctx *d;

		int next_prg;



		if (copy_from_user(&v, argp, sizeof(v)))

		if (unlikely(copy_from_user(&v, argp, sizeof(v))))

			return -EFAULT;



		d = find_ctx(&ctx->context_list, OHCI_ISO_RECEIVE, v.channel);

		if (d == NULL) return -EFAULT;

		if (unlikely(d == NULL))

			return -EFAULT;



		if ((v.buffer<0) || (v.buffer>=d->num_desc - 1)) {

		if (unlikely((v.buffer<0) || (v.buffer>=d->num_desc - 1))) {

			PRINT(KERN_ERR, ohci->host->id,

			      "Buffer %d out of range",v.buffer);

			return -EINVAL;
@@ -898,7 +899,7 @@ static int __video1394_ioctl(struct file *file, 


		spin_lock_irqsave(&d->lock,flags);



		if (d->buffer_status[v.buffer]==VIDEO1394_BUFFER_QUEUED) {

		if (unlikely(d->buffer_status[v.buffer]==VIDEO1394_BUFFER_QUEUED)) {

			PRINT(KERN_ERR, ohci->host->id,

			      "Buffer %d is already used",v.buffer);

			spin_unlock_irqrestore(&d->lock,flags);
@@ -949,13 +950,14 @@ static int __video1394_ioctl(struct file *file, 
		struct dma_iso_ctx *d;

		int i = 0;



		if (copy_from_user(&v, argp, sizeof(v)))

		if (unlikely(copy_from_user(&v, argp, sizeof(v))))

			return -EFAULT;



		d = find_ctx(&ctx->context_list, OHCI_ISO_RECEIVE, v.channel);

		if (d == NULL) return -EFAULT;

		if (unlikely(d == NULL))

			return -EFAULT;



		if ((v.buffer<0) || (v.buffer>d->num_desc - 1)) {

		if (unlikely((v.buffer<0) || (v.buffer>d->num_desc - 1))) {

			PRINT(KERN_ERR, ohci->host->id,

			      "Buffer %d out of range",v.buffer);

			return -EINVAL;
@@ -1008,7 +1010,7 @@ static int __video1394_ioctl(struct file *file, 
		spin_unlock_irqrestore(&d->lock, flags);



		v.buffer=i;

		if (copy_to_user(argp, &v, sizeof(v)))

		if (unlikely(copy_to_user(argp, &v, sizeof(v))))

			return -EFAULT;



		return 0;