From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eldad Zack Subject: [PATCH v3 07/11] ALSA: usb-audio: correct ep use_count semantics (add set_param flag) Date: Sun, 25 Aug 2013 17:45:51 +0200 Message-ID: <1377445555-5923-2-git-send-email-eldad@fogrefinery.com> References: <1377445399-5678-1-git-send-email-eldad@fogrefinery.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-bk0-f53.google.com (mail-bk0-f53.google.com [209.85.214.53]) by alsa0.perex.cz (Postfix) with ESMTP id 0627F2619DD for ; Sun, 25 Aug 2013 17:46:08 +0200 (CEST) Received: by mail-bk0-f53.google.com with SMTP id d7so827447bkh.12 for ; Sun, 25 Aug 2013 08:46:04 -0700 (PDT) In-Reply-To: <1377445399-5678-1-git-send-email-eldad@fogrefinery.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: Takashi Iwai , Clemens Ladisch , Daniel Mack Cc: alsa-devel@alsa-project.org, Eldad Zack List-Id: alsa-devel@alsa-project.org 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 --- v2: Cleaned up the patch, now it does only one thing (add the flag and the check). --- 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 5ecacaa..4061ee1 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 c6fcb7b..6ff36f5 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: @@ -765,11 +767,12 @@ 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); @@ -921,6 +924,7 @@ 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; set_bit(EP_FLAG_STOPPING, &ep->flags); } } -- 1.8.1.5