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Sat, 19 Sep 2026 21:56:22 -0700 (PDT) Received: from [192.168.2.3] ([2403:581e:d87e:0:fc2d:ed31:e80e:412d]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2ddc17d712dsm16026765ad.64.2026.09.19.21.56.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Sep 2026 21:56:22 -0700 (PDT) From: James Calligeros Date: Sun, 20 Sep 2026 14:53:47 +1000 Subject: [PATCH 08/28] ALSA: control: Add kcontrol callbacks for lock/unlock Precedence: bulk X-Mailing-List: asahi@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260920-macaudio-v1-8-741cc20a74e5@gmail.com> References: <20260920-macaudio-v1-0-741cc20a74e5@gmail.com> In-Reply-To: <20260920-macaudio-v1-0-741cc20a74e5@gmail.com> To: =?utf-8?q?Martin_Povi=C5=A1er?= , Liam Girdwood , Mark Brown , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Sven Peter , Janne Grunau , Neal Gompa , David Rhodes , Richard Fitzgerald , Jaroslav Kysela , Takashi Iwai , Ulf Hansson , Amit Kucheria , "Rafael J. Wysocki" , Lars-Peter Clausen , Vinod Koul , Matthias Brugger , AngeloGioacchino Del Regno , Shenghao Ding , Kevin Lu , Baojun Xu , Sen Wang , James Calligeros , James Schulman Cc: asahi@lists.linux.dev, linux-sound@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, patches@opensource.cirrus.com, Takashi Iwai , linux-mediatek@lists.infradead.org, Hector Martin X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=3895; i=jcalligeros99@gmail.com; h=from:subject:message-id; bh=hq0jHTZPh6rJ3zZLKaOltAD+GhyW13KMayUHUfC4/Ik=; b=owGbwMvMwCV2xczoYuD3ygTG02pJDFnr0xWKi03e3C3nqtgRqz/pt8BfFxWmzIUJDzd0z1yyQ +xM8rSijoksDGJcDJZiiiwbmoQ8Zhux3ewXqdwLM4eVCWSItEgDAxCwMPDlJuaVGukY6ZlqG+oZ GukY6xgxcHEKwFXzMjJ8eL7wzf8MQd22z17z9l5xy770g6Hcr9EtrWTa9LDvL//pMzL8E/n2a9W Jk6+Nsj5e3Tn3Oldm8T57U3k+3hWvjp+ZGVTHDQA= X-Developer-Key: i=jcalligeros99@gmail.com; a=openpgp; fpr=B08212489B3206D98F1479BDD43632D151F77960 From: Hector Martin This allows drivers to implement policy around locking/unlocking controls, such as enforcing that a group of controls may only be locked by the same process/file, and taking actions when the controls lock/unlock (such as granting special access on lock and resetting values on unlock). This is, in particular, useful to implement volume safety controls, such that only a particular process (that locks controls and completes a handshake) may increase volumes above a given safe limit. It also allows the volume to be automatically lowered if that process dies (which will trigger an implicit unlock). Signed-off-by: Hector Martin Signed-off-by: James Calligeros --- include/sound/control.h | 7 +++++++ sound/core/control.c | 16 ++++++++++++++-- 2 files changed, 21 insertions(+), 2 deletions(-) diff --git a/include/sound/control.h b/include/sound/control.h index 909db0d0485d..6b3ef6be5100 100644 --- a/include/sound/control.h +++ b/include/sound/control.h @@ -15,9 +15,12 @@ #define snd_kcontrol_chip(kcontrol) ((kcontrol)->private_data) struct snd_kcontrol; +struct snd_ctl_file; typedef int (snd_kcontrol_info_t) (struct snd_kcontrol * kcontrol, struct snd_ctl_elem_info * uinfo); typedef int (snd_kcontrol_get_t) (struct snd_kcontrol * kcontrol, struct snd_ctl_elem_value * ucontrol); typedef int (snd_kcontrol_put_t) (struct snd_kcontrol * kcontrol, struct snd_ctl_elem_value * ucontrol); +typedef int (snd_kcontrol_lock_t) (struct snd_kcontrol * kcontrol, struct snd_ctl_file *owner); +typedef void (snd_kcontrol_unlock_t) (struct snd_kcontrol * kcontrol); typedef int (snd_kcontrol_tlv_rw_t)(struct snd_kcontrol *kcontrol, int op_flag, /* SNDRV_CTL_TLV_OP_XXX */ unsigned int size, @@ -56,6 +59,8 @@ struct snd_kcontrol_new { snd_kcontrol_info_t *info; snd_kcontrol_get_t *get; snd_kcontrol_put_t *put; + snd_kcontrol_lock_t *lock; + snd_kcontrol_unlock_t *unlock; union { snd_kcontrol_tlv_rw_t *c; const unsigned int *p; @@ -75,6 +80,8 @@ struct snd_kcontrol { snd_kcontrol_info_t *info; snd_kcontrol_get_t *get; snd_kcontrol_put_t *put; + snd_kcontrol_lock_t *lock; + snd_kcontrol_unlock_t *unlock; union { snd_kcontrol_tlv_rw_t *c; const unsigned int *p; diff --git a/sound/core/control.c b/sound/core/control.c index 4199342d4ffe..c8aab9abd306 100644 --- a/sound/core/control.c +++ b/sound/core/control.c @@ -126,10 +126,12 @@ static int snd_ctl_release(struct inode *inode, struct file *file) scoped_guard(rwsem_write, &card->controls_rwsem) { list_for_each_entry(control, &card->controls, list) for (idx = 0; idx < control->count; idx++) - if (control->vd[idx].owner == ctl) + if (control->vd[idx].owner == ctl) { control->vd[idx].owner = NULL; + if (control->unlock) + control->unlock(control); + } } - snd_fasync_free(ctl->fasync); snd_ctl_empty_read_queue(ctl); put_pid(ctl->pid); @@ -306,6 +308,8 @@ struct snd_kcontrol *snd_ctl_new1(const struct snd_kcontrol_new *ncontrol, kctl->info = ncontrol->info; kctl->get = ncontrol->get; kctl->put = ncontrol->put; + kctl->lock = ncontrol->lock; + kctl->unlock = ncontrol->unlock; kctl->tlv.p = ncontrol->tlv.p; kctl->private_value = ncontrol->private_value; @@ -1487,6 +1491,12 @@ static int snd_ctl_elem_lock(struct snd_ctl_file *file, vd = &kctl->vd[snd_ctl_get_ioff(kctl, &id)]; if (vd->owner) return -EBUSY; + + if (kctl->lock) { + int err = kctl->lock(kctl, file); + if (err < 0) + return err; + } vd->owner = file; return 0; } @@ -1511,6 +1521,8 @@ static int snd_ctl_elem_unlock(struct snd_ctl_file *file, if (vd->owner != file) return -EPERM; vd->owner = NULL; + if (kctl->unlock) + kctl->unlock(kctl); return 0; } -- 2.55.0