linux-kernel - [PATCH] ALSA: firewire-lib: Fix 'amdtp_domain_start()' when no AMDTP_OUT

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Message-Id: <9c9a53a4905984a570ba5672cbab84f2027dedc1.1624560484.git.christophe.jaillet@wanadoo.fr>
Date:   Thu, 24 Jun 2021 20:49:36 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     clemens@...isch.de, o-takashi@...amocchi.jp, perex@...ex.cz,
        tiwai@...e.com
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>
Subject: [PATCH] ALSA: firewire-lib: Fix 'amdtp_domain_start()' when no AMDTP_OUT_STREAM stream is found

The intent here is to return an error code if we don't find what we are
looking for in the 'list_for_each_entry()' loop.

's' is not NULL if the list is empty or if we scan the complete list.
Introduce a new 'found' variable to handle such cases.

Fixes: 60dd49298ec5 ("ALSA: firewire-lib: handle several AMDTP streams in callback handler of IRQ target")
Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
We could test with" if (list_entry_is_head(s, &d->streams, list))"
instead, but I find it much less readable.
---
 sound/firewire/amdtp-stream.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/sound/firewire/amdtp-stream.c b/sound/firewire/amdtp-stream.c
index aad9778d1c4d..9be2260e4ca2 100644
--- a/sound/firewire/amdtp-stream.c
+++ b/sound/firewire/amdtp-stream.c
@@ -1943,6 +1943,7 @@ int amdtp_domain_start(struct amdtp_domain *d, unsigned int tx_init_skip_cycles,
 	unsigned int events_per_period = d->events_per_period;
 	unsigned int queue_size;
 	struct amdtp_stream *s;
+	bool found = false;
 	int err;
 
 	if (replay_seq) {
@@ -1955,10 +1956,12 @@ int amdtp_domain_start(struct amdtp_domain *d, unsigned int tx_init_skip_cycles,
 
 	// Select an IT context as IRQ target.
 	list_for_each_entry(s, &d->streams, list) {
-		if (s->direction == AMDTP_OUT_STREAM)
+		if (s->direction == AMDTP_OUT_STREAM) {
+			found = true;
 			break;
+		}
 	}
-	if (!s)
+	if (!found)
 		return -ENXIO;
 	d->irq_target = s;
 
-- 
2.30.2