At Sun, 6 Oct 2013 22:31:12 +0200, Eldad Zack wrote:
Currently, use_count is used in snd_usb_endpoint_set_params to ensure the parameters don't get changed for an in-use endpoint.
However, there is a subtle condition where this check fails - if hw_params is called on both substreams before calling prepare (for playback) or start trigger (for capture): the endpoint is not yet started, i.e., snd_usb_endpoint_start() does not yet increment use_count.
This adds a flag to check if the parameters are set, but does not omit checking the use_count.
Signed-off-by: Eldad Zack eldad@fogrefinery.com
v2: Cleaned up the patch, now it does only one thing (add the flag and the check).
I guess this logic doesn't work if a capture stream is re-prepared before started. I know that you'll change the capture stream starting in the later patch, but then this patch must be applied after that, because it implicitly assumes the scheme.
Takashi
sound/usb/card.h | 1 + sound/usb/endpoint.c | 6 +++++- 2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/sound/usb/card.h b/sound/usb/card.h index ca98a9b..1014136 100644 --- a/sound/usb/card.h +++ b/sound/usb/card.h @@ -51,6 +51,7 @@ struct snd_usb_endpoint { struct snd_usb_audio *chip;
int use_count;
- bool param_set; int ep_num; /* the referenced endpoint number */ int type; /* SND_USB_ENDPOINT_TYPE_* */ unsigned long flags;
diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c index 2685660..9acc864 100644 --- a/sound/usb/endpoint.c +++ b/sound/usb/endpoint.c @@ -472,6 +472,8 @@ struct snd_usb_endpoint *snd_usb_add_endpoint(struct snd_usb_audio *chip, ep->syncmaxsize = le16_to_cpu(get_endpoint(alts, 1)->wMaxPacketSize); }
- ep->param_set = false;
- list_add_tail(&ep->list, &chip->ep_list);
__exit_unlock: @@ -780,11 +782,12 @@ int snd_usb_endpoint_set_params(struct snd_usb_endpoint *ep, { int err;
- if (ep->use_count != 0) {
if (ep->param_set || ep->use_count != 0) { snd_printk(KERN_WARNING "Unable to change format on ep #%x: already in use\n", ep->ep_num); return -EBUSY; }
ep->param_set = true;
/* release old buffers, if any */ release_urbs(ep, 0);
@@ -937,6 +940,7 @@ void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep) ep->sync_slave = NULL; ep->retire_data_urb = NULL; ep->prepare_data_urb = NULL;
ep->param_set = false;}
1.8.1.5