From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=74.125.82.53 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793981935; b=ooLTNz6e9g2A1ga3cwXRTiJ7F//pEStCxQVtpEWBYQvDZfKnddZJiTBDYaw28IFRJQuB /0r6uVG/OmrVjvq8CnDZNRezxd39oYKaxvijkYOQBc+Zm9YaKDL6qfc6loBu6J6DIyz+3 wc0LYtmE9SUn86VXxLuDqkyt7oVGfQk4q+8ubFfcZX4L5pEBZVWtNTlUFwPa9ZzR8Dlqr UFKj2Wwe3xvLNqj5hrLZDaB1eoIqvFxfwGTcOB67Nr/CwmEoBB3LTF6QO42pUckSJmelh 4ZydZl12/Tu6zn/kwFxpjA3CeCwBeB7YruA+KIa3QELPilB/W1VGzM/QlHtnGnPMUtQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793981935; h=DMARC-Filter:Received:DKIM-Signature:X-Google-DKIM-Signature: X-Forwarded-Encrypted:X-Gm-Message-State:X-Gm-Gg:X-Received:Received: From:To:Cc:Subject:Date:Message-ID:X-Mailer:In-Reply-To:References: MIME-Version:Content-Transfer-Encoding; bh=K9g1EmpJPl3VsiiyXPfTHGa4seP6cTbErFussR8Q6f4=; b=gHrCPnRVZxVrMNPvjNCIBYsH9VS0WRKmoleCrltXT46opD2zgeH/6JylZdPqxMNveiG2 FWIcWMnjWA6/Z6s3DxWASURvC9KJNTIEaAQuQcKmkPD6Qy7eMCM2SoiK23RC6o4go5Zdi RNyIZ8Spu0KVdPAFQ5MuEMDmeKFb/IohxEGgoZMqD+EUDh5vserxD1XLvdBsSUsOtTkmG q2shw7gDEL7KzgnwrNXQnAY9+KrpLBkXcKAfLHNdCXH/EmxfH7A9+vI9CJVOh4fUyY0n2 Gu3ScRnTfHmA0vxCT1MhY+tOiww132gSld5cQX0VPluWVi8b0kkuA+vNHZpN/pzOOGg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20260707 header.b=KejBBg8P; arc=none smtp.remote-ip=74.125.82.53 Received: from mail-dl1-f53.google.com (mail-dl1-f53.google.com [74.125.82.53]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DB410606A32F for ; Fri, 6 Nov 2026 16:18:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org DB410606A32F Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20260707 header.b=KejBBg8P Received: by mail-dl1-f53.google.com with SMTP id a92af1059eb24-15dd124bbe7so1671365c88.1 for ; Fri, 06 Nov 2026 08:18:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20260707; t=1793981934; x=1794586734; darn=lists.linux.dev; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=K9g1EmpJPl3VsiiyXPfTHGa4seP6cTbErFussR8Q6f4=; b=KejBBg8PtT2ldMIeKcn7jGbOzsvDUKzNG9K+8D2gXDnyW9pQLJWy8uED28nofXtSVv JFN6eDQXBpF+Xy+Qla04SLpDfOEZA0JivTXufdJ3HoNRHT1aifIWIbZkNYyrip7POL8s 6wyq7Kh87Q2TDBmSESnTTkuJXtKzacUXuE48ygBcCZHdP+3eekETbpC3KGW6SpNtOsRr 0zHuy/oU1lWtG1/b4rYUmoRTMpc611q8pm3Q6IQ3KeiagYz+qcYNjs5B3r939j9udg3m JdMAomLRFzD8zc5Dtp82qkelY9+265DKc6YLV7m/OuyJ13JHHmdM2s34r6DNEPtg8Enk pavw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1793981934; x=1794586734; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=K9g1EmpJPl3VsiiyXPfTHGa4seP6cTbErFussR8Q6f4=; b=yoE+n69apiCChUOKOEzCPJJJEUw5W19Q88hdg447nVFesYZv1bNj+tAqKqyJfLCDrK /iMrVmoOTQI5ex5gvOWaUBtoPXKpWbTWny52F3isOgCK8xKDLSp1CFzZF9IOWH3deBCD Lo0mjdPNwN6ZoQFLQ31QafsQ3M58sIb291r9M/cNzT9pNgQINfUoslldO4g8HrLOhBQr jAobT17dth2JIzc/Xmv9RGKewjVWCGjYWvGPq2/94bDu1Z0kVDru2CfmK7GbpZn0QWmR a1DSLKjkLcW9R524SLHVKUR/PpH33b5X4PpMLY/81DzGzofMmRP2UapYTBPv6PXiLWDD WhOw== X-Forwarded-Encrypted: i=1; AKwUvBzgvCTw0lATEzvaanTPnR3RK17qS11EAA/uXeqSl2GktdRQb1SzDcaf305laCIgRNPloGplhfRdurYt8GxUKA==@lists.linux.dev X-Gm-Message-State: APuU4Z9t94njFQLZtRBjs69oL4SNF1+/eVxc3TU66szP0y6E7WWYFzz/ u+P6392pU0mrxEetC3JRyY5SUx39meELVvR0FFMOf/F2Ba7wzgIxEyWc X-Gm-Gg: AYBFou1y9dLKrvEVMFgIj2JdOsTpjqg1Tin3sHE84/J4ELpaUKQEG6pgz1GmMXD95Ya EHz4O/TFWaiQN4Fobi7/+GTUz8f99VZtcR1cYLRITmWEEZi/xupjbqMojWHdIhcl+i0A0EdqUf2 2Oedq2JPgBIyU/rYMibAZBQInaCuLdEvrZHqGnG3MiDeLDHTXeXgFfk5ogDxjql/w/GYwNGrmF5 dzepyq8BfcMJ/Ym7KfkIzwLPA2CVZ9kAFGoJEedv2WOGTwufVN9n6GfjDBCMAZgZEmVnNRHCWCw pUB7K0VU7HJlsXn7G2BexUaWTpqgeW8HzeBVLPQ1gahsy39LxuddcNSlzGvQC/3MjyQz6gCt7ub H7MZwG9YfMorkNanHZ15w04uplhJuc13MtChebdfjKo3IkUJKy6+cbyCx9YhF4UCr00E0SRESoW TSHwgAzgzJPUiGbI3NFXUwKaGjAW/pbLh8TlSIw30uKHkJfo5YXdOu/NOU5pkNF1gZKTf8SWGhQ Miyk9nI71u+cVog2yXNZODy/AAouZjeS8TDb2XQauVMGdn7ih5jqYk2UpEsogdeBt314hV/QpSn lhCugCa3PKUOkgvfOAHKgl8I7EngvJa1mCDz8gyAZVrq8hXGnLRG7fRUJz92/SP/FsYGF2Ja/90 xHKn+otaZsVAlyGdjGGLZA9QkvQa85ygPZnARTKiOitAfAPrctypOhaskYy1GgXM05To= X-Received: by 2002:a05:701b:2916:b0:17a:e684:b497 with SMTP id a92af1059eb24-1b25d293b87mr3742048c88.5.1793981933956; Fri, 06 Nov 2026 08:18:53 -0800 (PST) Received: from localhost.localdomain ([180.182.24.11]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-1b25e4840f3sm13139526c88.5.2026.11.06.08.18.51 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Fri, 06 Nov 2026 08:18:53 -0800 (PST) From: Joonho Lee To: linux-sound@vger.kernel.org Cc: tiwai@suse.com, perex@perex.cz, anton.yakovlev@opensynergy.com, mst@redhat.com, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, corbet@lwn.net, skhan@linuxfoundation.org, rdunlap@infradead.org, linux-doc@vger.kernel.org, Joonho Lee Subject: [PATCH v19 03/12] ALSA: pcm: add an optional reset operation under the stream lock Date: Sat, 7 Nov 2026 01:18:29 +0900 Message-ID: <20261106161838.94308-4-mynameisjune111@gmail.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20261106161838.94308-1-mynameisjune111@gmail.com> References: <20261106161838.94308-1-mynameisjune111@gmail.com> X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit A driver may need to synchronize private capture accounting with the common RESET pointer observation and the core's position rebase. Add an optional reset operation called under the member's stream lock. Expose snd_pcm_lib_reset() so the callback can retain common pointer and time handling. On zero return the core completes that member's rebase before unlocking it. Drivers without the callback retain the ioctl path. The operation is also used after a successful prepare. Zero permits the position rebase; it does not promise XRUN recovery. A negative return skips the core rebase, so a callback returning an error must leave coherent pointer state even after partial work. Linked RESET and prepare stop at the first error without rollback. Earlier callback members may already have completed. Legacy members keep the existing post_action policy. Applications must recover the group after partial failure before relying on shared positions. This adds an internal kernel operation and no userspace ioctl or layout. Out-of-tree modules using snd_pcm_ops need to be rebuilt. Complete appl_ptr rebasing once in the callback path. A later linked member can sleep in prepare while the earlier member accepts SYNC_PTR; a subsequent unlocked post_prepare assignment would overwrite that acknowledgment. Keep explicit RESET playback silence processing and leave prepare-time filling to the normal START path, preserving samples written and rewound after prepare. Signed-off-by: Joonho Lee --- include/sound/pcm.h | 21 +++++++++++++++++++++ sound/core/pcm_lib.c | 29 ++++++++++++++++++++++++----- sound/core/pcm_native.c | 45 ++++++++++++++++++++++++++++++++++++++++----- 3 files changed, 85 insertions(+), 10 deletions(-) diff --git a/include/sound/pcm.h b/include/sound/pcm.h --- a/include/sound/pcm.h +++ b/include/sound/pcm.h @@ -77,6 +77,26 @@ unsigned long offset); int (*mmap)(struct snd_pcm_substream *substream, struct vm_area_struct *vma); int (*ack)(struct snd_pcm_substream *substream); + /* + * Optional RESET operation, also used after a successful prepare. + * Called with this substream's PCM lock held; atomic streams must not + * sleep. Do not reacquire the PCM lock through snd_pcm_lib_ioctl(). + * snd_pcm_lib_reset() provides the common pointer update under this + * lock. The core completes the position and appl_ptr rebase before + * unlocking a successful member. + * + * Return zero to let the core complete the position rebase. As with + * the legacy RESET ioctl, zero does not guarantee recovery from XRUN; + * callers must still handle the stream state and subsequent I/O errors. + * On a negative return the core does not finish the rebase, so the + * callback must leave coherent pointer state even after partial work. + * + * Linked RESET/prepare + * stops at the first error without rollback. Earlier callback members + * retain their completed reset; legacy members retain the existing + * post_action policy. An error does not guarantee unchanged state. + */ + int (*reset)(struct snd_pcm_substream *substream); }; /* @@ -1179,6 +1199,7 @@ { substream->runtime->std_sync_id = true; } +int snd_pcm_lib_reset(struct snd_pcm_substream *substream); int snd_pcm_lib_ioctl(struct snd_pcm_substream *substream, unsigned int cmd, void *arg); void snd_pcm_period_elapsed_under_stream_lock(struct snd_pcm_substream *substream); diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c --- a/sound/core/pcm_lib.c +++ b/sound/core/pcm_lib.c @@ -1760,20 +1760,39 @@ } EXPORT_SYMBOL(snd_pcm_hw_params_bits); -static int snd_pcm_lib_ioctl_reset(struct snd_pcm_substream *substream, - void *arg) +/** + * snd_pcm_lib_reset - Reset the pointer while holding the PCM stream lock + * @substream: PCM substream + * + * Context: PCM stream lock held. The caller must not hold driver locks + * acquired by the pointer or XRUN callbacks. + * + * Update a running stream through the ordinary pointer path. Other states + * start at zero. Pointer errors keep the existing RESET return semantics; + * a zero return does not imply recovery from XRUN. + * This helper does not update appl_ptr or acquire the stream lock. + * + * Return: zero. + */ +int snd_pcm_lib_reset(struct snd_pcm_substream *substream) { struct snd_pcm_runtime *runtime = substream->runtime; - guard(pcm_stream_lock_irqsave)(substream); - if (snd_pcm_running(substream) && - snd_pcm_update_hw_ptr(substream) >= 0) + if (snd_pcm_running(substream) && snd_pcm_update_hw_ptr(substream) >= 0) runtime->status->hw_ptr %= runtime->buffer_size; else { runtime->status->hw_ptr = 0; runtime->hw_ptr_wrap = 0; } return 0; +} +EXPORT_SYMBOL(snd_pcm_lib_reset); + +static int snd_pcm_lib_ioctl_reset(struct snd_pcm_substream *substream, + void *arg) +{ + guard(pcm_stream_lock_irqsave)(substream); + return snd_pcm_lib_reset(substream); } static int snd_pcm_lib_ioctl_channel_info(struct snd_pcm_substream *substream, diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -1984,11 +1984,35 @@ } } -static int snd_pcm_do_reset(struct snd_pcm_substream *substream, - snd_pcm_state_t state) +static int snd_pcm_reset_substream(struct snd_pcm_substream *substream, + bool for_prepare) { struct snd_pcm_runtime *runtime = substream->runtime; - int err = snd_pcm_ops_ioctl(substream, SNDRV_PCM_IOCTL1_RESET, NULL); + int err; + + if (substream->ops->reset) { + /* + * Complete this member before releasing its PCM lock. A later + * linked member may fail; RESET has no group rollback operation. + */ + guard(pcm_stream_lock_irq)(substream); + + err = substream->ops->reset(substream); + if (err < 0) + return err; + runtime->hw_ptr_base = 0; + runtime->hw_ptr_interrupt = runtime->status->hw_ptr - + runtime->status->hw_ptr % runtime->period_size; + runtime->silence_start = runtime->status->hw_ptr; + runtime->silence_filled = 0; + runtime->control->appl_ptr = runtime->status->hw_ptr; + if (!for_prepare && substream->stream == SNDRV_PCM_STREAM_PLAYBACK && + runtime->silence_size > 0) + snd_pcm_playback_silence(substream, ULONG_MAX); + return 0; + } + + err = snd_pcm_ops_ioctl(substream, SNDRV_PCM_IOCTL1_RESET, NULL); if (err < 0) return err; guard(pcm_stream_lock_irq)(substream); @@ -2000,10 +2024,19 @@ return 0; } +static int snd_pcm_do_reset(struct snd_pcm_substream *substream, + snd_pcm_state_t state) +{ + return snd_pcm_reset_substream(substream, false); +} + static void snd_pcm_post_reset(struct snd_pcm_substream *substream, snd_pcm_state_t state) { struct snd_pcm_runtime *runtime = substream->runtime; + + if (substream->ops->reset) + return; guard(pcm_stream_lock_irq)(substream); runtime->control->appl_ptr = runtime->status->hw_ptr; if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK && @@ -2053,14 +2086,16 @@ if (err < 0) return err; pcm_qos_req_update(substream, period_to_usecs(substream->runtime)); - return snd_pcm_do_reset(substream, state); + return snd_pcm_reset_substream(substream, true); } static void snd_pcm_post_prepare(struct snd_pcm_substream *substream, snd_pcm_state_t state) { struct snd_pcm_runtime *runtime = substream->runtime; - runtime->control->appl_ptr = runtime->status->hw_ptr; + /* The reset callback path already completed this rebase under the lock. */ + if (!substream->ops->reset) + runtime->control->appl_ptr = runtime->status->hw_ptr; snd_pcm_set_state(substream, SNDRV_PCM_STATE_PREPARED); }