linux-2.6.33/snd_pcm_lib_writev_transfer() の履歴(No.2)

• 履歴一覧
• 差分 を表示
• 現在との差分 を表示
• ソース を表示
• linux-2.6.33/snd_pcm_lib_writev_transfer() へ行く。
  • 1 (2013-06-28 (金) 09:24:34)
  • 2 (2013-06-28 (金) 09:24:51)

参照元†

• linux-2.6.33/snd_pcm_lib_writev()

説明†

• パス: linux-2.6.33/sound/core/pcm_lib.c

• FIXME: これは何？
  • 説明

引数†

• struct snd_pcm_substream *substream
  • linux-2.6.33/snd_pcm_substream
• unsigned int hwoff
• unsigned long data
• unsigned int off
• snd_pcm_uframes_t frames
  • linux-2.6.33/snd_pcm_uframes_t

返り値†

• int

参考†

実装†

static int snd_pcm_lib_writev_transfer(struct snd_pcm_substream *substream,
				       unsigned int hwoff,
				       unsigned long data, unsigned int off,
				       snd_pcm_uframes_t frames)
{
	struct snd_pcm_runtime *runtime = substream->runtime;
	int err;
	void __user **bufs = (void __user **)data;
	int channels = runtime->channels;
	int c;

• • linux-2.6.33/snd_pcm_runtime

	if (substream->ops->copy) {
		if (snd_BUG_ON(!substream->ops->silence))
			return -EINVAL;

• • substream->ops は snd_pcm_ops 型のメンバ
  • linux-2.6.33/snd_pcm_ops

• linux-2.6.33/snd_BUG_ON()

		for (c = 0; c < channels; ++c, ++bufs) {
			if (*bufs == NULL) {
				if ((err = substream->ops->silence(substream, c, hwoff, frames)) < 0)
					return err;
			} else {
				char __user *buf = *bufs + samples_to_bytes(runtime, off);
				if ((err = substream->ops->copy(substream, c, hwoff, buf, frames)) < 0)
					return err;
			}
		}

• • substream->ops は snd_pcm_ops 型のメンバ
  • linux-2.6.33/snd_pcm_ops

	} else {
		/* default transfer behaviour */
		size_t dma_csize = runtime->dma_bytes / channels;
		for (c = 0; c < channels; ++c, ++bufs) {
			char *hwbuf = runtime->dma_area + (c * dma_csize) + samples_to_bytes(runtime, hwoff);
			if (*bufs == NULL) {
				snd_pcm_format_set_silence(runtime->format, hwbuf, frames);
			} else {
				char __user *buf = *bufs + samples_to_bytes(runtime, off);
				if (copy_from_user(hwbuf, buf, samples_to_bytes(runtime, frames)))
					return -EFAULT;
			}
		}

• • linux-2.6.33/samples_to_bytes()

• linux-2.6.33/snd_pcm_format_set_silence()

• • linux-2.6.33/copy_from_user()

	}
	return 0;
}

コメント†