diff options
Diffstat (limited to 'Documentation/sound/kernel-api')
| -rw-r--r-- | Documentation/sound/kernel-api/writing-an-alsa-driver.rst | 35 |
1 files changed, 13 insertions, 22 deletions
diff --git a/Documentation/sound/kernel-api/writing-an-alsa-driver.rst b/Documentation/sound/kernel-api/writing-an-alsa-driver.rst index b37234afdfa1..6b154dbb02cc 100644 --- a/Documentation/sound/kernel-api/writing-an-alsa-driver.rst +++ b/Documentation/sound/kernel-api/writing-an-alsa-driver.rst @@ -3520,14 +3520,14 @@ allocator will try to get an area as large as possible within the given size. The second argument (type) and the third argument (device pointer) are -dependent on the bus. In the case of the ISA bus, pass -:c:func:`snd_dma_isa_data()` as the third argument with +dependent on the bus. For normal devices, pass the device pointer +(typically identical as ``card->dev``) to the third argument with ``SNDRV_DMA_TYPE_DEV`` type. For the continuous buffer unrelated to the bus can be pre-allocated with ``SNDRV_DMA_TYPE_CONTINUOUS`` type and the ``snd_dma_continuous_data(GFP_KERNEL)`` device pointer, where -``GFP_KERNEL`` is the kernel allocation flag to use. For the PCI -scatter-gather buffers, use ``SNDRV_DMA_TYPE_DEV_SG`` with -``snd_dma_pci_data(pci)`` (see the `Non-Contiguous Buffers`_ +``GFP_KERNEL`` is the kernel allocation flag to use. For the +scatter-gather buffers, use ``SNDRV_DMA_TYPE_DEV_SG`` with the device +pointer (see the `Non-Contiguous Buffers`_ section). Once the buffer is pre-allocated, you can use the allocator in the @@ -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 |