From 910e7e1923d52a74183d3aedd45f7fa4c3585400 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Tue, 15 Jan 2019 10:49:47 +0100 Subject: [PATCH] ALSA: doc: Update the description about PCM suspend procedure The PCM suspend procedure was changed for drivers, so that they don't have to call snd_pcm_suspend*() in each callback any longer. Update the documentation to adapt the changes. Reviewed-by: Jaroslav Kysela Signed-off-by: Takashi Iwai --- .../sound/kernel-api/writing-an-alsa-driver.rst | 25 +++++++--------------- 1 file changed, 8 insertions(+), 17 deletions(-) diff --git a/Documentation/sound/kernel-api/writing-an-alsa-driver.rst b/Documentation/sound/kernel-api/writing-an-alsa-driver.rst index b37234a..7c2f203 100644 --- a/Documentation/sound/kernel-api/writing-an-alsa-driver.rst +++ b/Documentation/sound/kernel-api/writing-an-alsa-driver.rst @@ -3924,15 +3924,12 @@ The scheme of the real suspend job is as follows. 2. Call :c:func:`snd_power_change_state()` with ``SNDRV_CTL_POWER_D3hot`` to change the power status. -3. Call :c:func:`snd_pcm_suspend_all()` to suspend the running - PCM streams. - -4. If AC97 codecs are used, call :c:func:`snd_ac97_suspend()` for +3. If AC97 codecs are used, call :c:func:`snd_ac97_suspend()` for each codec. -5. Save the register values if necessary. +4. Save the register values if necessary. -6. Stop the hardware if necessary. +5. Stop the hardware if necessary. A typical code would be like: @@ -3946,12 +3943,10 @@ A typical code would be like: /* (2) */ snd_power_change_state(card, SNDRV_CTL_POWER_D3hot); /* (3) */ - snd_pcm_suspend_all(chip->pcm); - /* (4) */ snd_ac97_suspend(chip->ac97); - /* (5) */ + /* (4) */ snd_mychip_save_registers(chip); - /* (6) */ + /* (5) */ snd_mychip_stop_hardware(chip); return 0; } @@ -3994,13 +3989,9 @@ A typical code would be like: return 0; } -As shown in the above, it's better to save registers after suspending -the PCM operations via :c:func:`snd_pcm_suspend_all()` or -:c:func:`snd_pcm_suspend()`. It means that the PCM streams are -already stopped when the register snapshot is taken. But, remember that -you don't have to restart the PCM stream in the resume callback. It'll -be restarted via trigger call with ``SNDRV_PCM_TRIGGER_RESUME`` when -necessary. +Note that, at the time this callback gets called, the PCM stream has +been already suspended via its own PM ops calling +:c:func:`snd_pcm_suspend_all()` internally. OK, we have all callbacks now. Let's set them up. In the initialization of the card, make sure that you can get the chip data from the card -- 2.7.4