From 29b16931f936fdbcd78995e66d0f5626f3afbda8 Mon Sep 17 00:00:00 2001 From: Clemens Ladisch Date: Fri, 13 May 2005 07:50:28 +0200 Subject: [PATCH] [ALSA] usb-audio - avoid unnecessary double buffering USB generic driver When a USB packet boundary falls exactly on a buffer boundary, hwptr remains at the end of the buffer which causes an overflow in the next iteration and triggers double buffering although the next packet would actually be contiguous. This patch ensures that hwptr is always smaller than buffer_size. Signed-off-by: Clemens Ladisch --- sound/usb/usbaudio.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c index a6ed0d08337e..076da19a9e28 100644 --- a/sound/usb/usbaudio.c +++ b/sound/usb/usbaudio.c @@ -565,6 +565,8 @@ static int prepare_playback_urb(snd_usb_substream_t *subs, /* set the buffer pointer */ urb->transfer_buffer = runtime->dma_area + subs->hwptr * stride; subs->hwptr += offs; + if (subs->hwptr == runtime->buffer_size) + subs->hwptr = 0; } spin_unlock_irqrestore(&subs->lock, flags); urb->transfer_buffer_length = offs * stride;