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Diffstat (limited to 'Documentation/sound/alsa/ALSA-Configuration.txt')
| -rw-r--r-- | Documentation/sound/alsa/ALSA-Configuration.txt | 36 |
1 files changed, 34 insertions, 2 deletions
diff --git a/Documentation/sound/alsa/ALSA-Configuration.txt b/Documentation/sound/alsa/ALSA-Configuration.txt index 226013035d7..812ed2b80b8 100644 --- a/Documentation/sound/alsa/ALSA-Configuration.txt +++ b/Documentation/sound/alsa/ALSA-Configuration.txt @@ -671,7 +671,8 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed. module did formerly. It will allocate the buffers in advance when any HDSP cards are found. To make the buffer allocation sure, load snd-page-alloc module in the early - stage of boot sequence. + stage of boot sequence. See "Early Buffer Allocation" + section. Module snd-ice1712 ------------------ @@ -1067,7 +1068,8 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed. module did formerly. It will allocate the buffers in advance when any RME9652 cards are found. To make the buffer allocation sure, load snd-page-alloc module in the early - stage of boot sequence. + stage of boot sequence. See "Early Buffer Allocation" + section. Module snd-sa11xx-uda1341 (on arm only) --------------------------------------- @@ -1545,6 +1547,36 @@ Proc interfaces (/proc/asound) echo "rvplayer 0 0 block" > /proc/asound/card0/pcm0p/oss +Early Buffer Allocation +======================= + +Some drivers (e.g. hdsp) require the large contiguous buffers, and +sometimes it's too late to find such spaces when the driver module is +actually loaded due to memory fragmentation. You can pre-allocate the +PCM buffers by loading snd-page-alloc module and write commands to its +proc file in prior, for example, in the early boot stage like +/etc/init.d/*.local scripts. + +Reading the proc file /proc/drivers/snd-page-alloc shows the current +usage of page allocation. In writing, you can send the following +commands to the snd-page-alloc driver: + + - add VENDOR DEVICE MASK SIZE BUFFERS + + VENDOR and DEVICE are PCI vendor and device IDs. They take + integer numbers (0x prefix is needed for the hex). + MASK is the PCI DMA mask. Pass 0 if not restricted. + SIZE is the size of each buffer to allocate. You can pass + k and m suffix for KB and MB. The max number is 16MB. + BUFFERS is the number of buffers to allocate. It must be greater + than 0. The max number is 4. + + - erase + + This will erase the all pre-allocated buffers which are not in + use. + + Links ===== |