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[177.4.161.78]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2c16ec7f9c9sm5890932eec.12.2026.03.26.22.22.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 26 Mar 2026 22:22:34 -0700 (PDT) Message-ID: <1cac7d61-94e2-427c-ab7a-1b114df62870@gmail.com> Date: Fri, 27 Mar 2026 02:22:30 -0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] ASoC: generic: keep fallback dai_name stable across rebind To: Mark Brown , Kuninori Morimoto , Liam Girdwood , Jaroslav Kysela , Takashi Iwai Cc: linux-sound@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260327-asoc-generic-fallback-dai-name-rebind-v2-1-1368c57c4a0d@gmail.com> From: =?UTF-8?Q?C=C3=A1ssio_Gabriel_Monteiro_Pires?= Content-Language: en-US In-Reply-To: <20260327-asoc-generic-fallback-dai-name-rebind-v2-1-1368c57c4a0d@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 3/27/26 01:11, Cássio Gabriel wrote: > simple_parse_dai() and graph_util_parse_dai() first try to identify a > DAI via dai_args. When that works the card can rebind without relying on > dlc->dai_name. > > The fallback path still calls snd_soc_get_dlc(), which returns a > borrowed dai_name pointer. If the CPU or codec component is unbound > while the sound card stays registered, the generic card keeps that > pointer and the next rebind may compare stale memory while matching the > DAI. > > Stage the fallback result in a temporary dai_link_component and move > only a card-owned copy of dai_name into the live link component. Use > devm_kstrdup_const() so static names are reused and dynamic ones remain > valid for the lifetime of the card device. > > Signed-off-by: Cássio Gabriel > Acked-by: Kuninori Morimoto > --- > Changes in v2: > - Rework simple_parse_dai() and graph_util_parse_dai() to use if/else > instead of a non-error goto. > - Move the fallback snd_soc_get_dlc() handling into the else branch. > - Link to v1: https://patch.msgid.link/20260326-asoc-generic-fallback-dai-name-rebind-v1-1-ac9da3cbd606@gmail.com > --- > sound/soc/generic/simple-card-utils.c | 52 ++++++++++++++++------------------- > sound/soc/generic/simple-card.c | 46 ++++++++++++++----------------- > 2 files changed, 44 insertions(+), 54 deletions(-) > > diff --git a/sound/soc/generic/simple-card-utils.c b/sound/soc/generic/simple-card-utils.c > index da6353594d61..e5cb602fd248 100644 > --- a/sound/soc/generic/simple-card-utils.c > +++ b/sound/soc/generic/simple-card-utils.c > @@ -1128,7 +1128,9 @@ int graph_util_parse_dai(struct simple_util_priv *priv, struct device_node *ep, > struct device *dev = simple_priv_to_dev(priv); > struct device_node *node; > struct of_phandle_args args = {}; > + struct snd_soc_dai_link_component resolved_dlc = {}; > struct snd_soc_dai *dai; > + const char *fallback_dai_name; > int ret; > > if (!ep) > @@ -1152,39 +1154,31 @@ int graph_util_parse_dai(struct simple_util_priv *priv, struct device_node *ep, > dlc->of_node = node; > dlc->dai_name = dai_name; > dlc->dai_args = dai_args; > + } else { > + /* Get dai->name */ > + args.np = node; > + args.args[0] = graph_get_dai_id(ep); > + args.args_count = (of_graph_get_endpoint_count(node) > 1); > > - goto parse_dai_end; > - } > + ret = snd_soc_get_dlc(&args, &resolved_dlc); > + if (ret < 0) > + goto err; > > - /* Get dai->name */ > - args.np = node; > - args.args[0] = graph_get_dai_id(ep); > - args.args_count = (of_graph_get_endpoint_count(node) > 1); > + /* Keep fallback dai_name valid across component rebind */ > + fallback_dai_name = resolved_dlc.dai_name; > + if (fallback_dai_name) { > + fallback_dai_name = devm_kstrdup_const(dev, fallback_dai_name, > + GFP_KERNEL); > + ret = -ENOMEM; > + if (!fallback_dai_name) > + goto err; > + } > > - /* > - * FIXME > - * > - * Here, dlc->dai_name is pointer to CPU/Codec DAI name. > - * If user unbinded CPU or Codec driver, but not for Sound Card, > - * dlc->dai_name is keeping unbinded CPU or Codec > - * driver's pointer. > - * > - * If user re-bind CPU or Codec driver again, ALSA SoC will try > - * to rebind Card via snd_soc_try_rebind_card(), but because of > - * above reason, it might can't bind Sound Card. > - * Because Sound Card is pointing to released dai_name pointer. > - * > - * To avoid this rebind Card issue, > - * 1) It needs to alloc memory to keep dai_name eventhough > - * CPU or Codec driver was unbinded, or > - * 2) user need to rebind Sound Card everytime > - * if he unbinded CPU or Codec. > - */ > - ret = snd_soc_get_dlc(&args, dlc); > - if (ret < 0) > - goto err; > + dlc->of_node = resolved_dlc.of_node; > + dlc->dai_name = fallback_dai_name; > + dlc->dai_args = resolved_dlc.dai_args; > + } > > -parse_dai_end: > if (is_single_link) > *is_single_link = of_graph_get_endpoint_count(node) == 1; > ret = 0; > diff --git a/sound/soc/generic/simple-card.c b/sound/soc/generic/simple-card.c > index 9937a991846e..b24ba1330896 100644 > --- a/sound/soc/generic/simple-card.c > +++ b/sound/soc/generic/simple-card.c > @@ -69,7 +69,9 @@ static int simple_parse_dai(struct simple_util_priv *priv, > { > struct device *dev = simple_priv_to_dev(priv); > struct of_phandle_args args; > + struct snd_soc_dai_link_component resolved_dlc = {}; > struct snd_soc_dai *dai; > + const char *fallback_dai_name; > int ret; > > if (!node) > @@ -94,34 +96,28 @@ static int simple_parse_dai(struct simple_util_priv *priv, > dlc->dai_args = snd_soc_copy_dai_args(dev, &args); > if (!dlc->dai_args) > goto end; > + } else { > + ret = snd_soc_get_dlc(&args, &resolved_dlc); > + if (ret < 0) > + goto end; > > - goto parse_dai_end; > - } > + /* Keep fallback dai_name valid across component rebind */ > + fallback_dai_name = resolved_dlc.dai_name; > + if (fallback_dai_name) { > + fallback_dai_name = devm_kstrdup_const(dev, fallback_dai_name, > + GFP_KERNEL); > + ret = -ENOMEM; > + if (!fallback_dai_name) { > + of_node_put(resolved_dlc.of_node); > + goto end; > + } > + } > > - /* > - * FIXME > - * > - * Here, dlc->dai_name is pointer to CPU/Codec DAI name. > - * If user unbinded CPU or Codec driver, but not for Sound Card, > - * dlc->dai_name is keeping unbinded CPU or Codec > - * driver's pointer. > - * > - * If user re-bind CPU or Codec driver again, ALSA SoC will try > - * to rebind Card via snd_soc_try_rebind_card(), but because of > - * above reason, it might can't bind Sound Card. > - * Because Sound Card is pointing to released dai_name pointer. > - * > - * To avoid this rebind Card issue, > - * 1) It needs to alloc memory to keep dai_name eventhough > - * CPU or Codec driver was unbinded, or > - * 2) user need to rebind Sound Card everytime > - * if he unbinded CPU or Codec. > - */ > - ret = snd_soc_get_dlc(&args, dlc); > - if (ret < 0) > - goto end; > + dlc->of_node = resolved_dlc.of_node; > + dlc->dai_name = fallback_dai_name; > + dlc->dai_args = resolved_dlc.dai_args; > + } > > -parse_dai_end: > if (is_single_link) > *is_single_link = !args.args_count; > ret = 0; > > --- > base-commit: d084fd53a2fd5748d4317635b1c1a7dba7edf583 > change-id: 20260326-asoc-generic-fallback-dai-name-rebind-6381a1c807fd > > Best regards, > -- > Cássio Gabriel > I forgot to add the 'Suggested-by' tag attributing the suggestion made by Kuninori. I apologize. Should I send a v3 patch adding the tag? -- Thanks, Cássio