static ssize_t snd_compr_write(struct file *f, const char __user *buf,
		size_t count, loff_t *offset)
{
	struct snd_compr_file *data = f->private_data;
	struct snd_compr_stream *stream;
	size_t avail;
	int retval;

	if (snd_BUG_ON(!data))
		return -EFAULT;

	stream = &data->stream;
	mutex_lock(&stream->device->lock);
	/* write is allowed when stream is running or has been steup */
	if (stream->runtime->state != SNDRV_PCM_STATE_SETUP &&
			stream->runtime->state != SNDRV_PCM_STATE_RUNNING) {
		mutex_unlock(&stream->device->lock);
		return -EBADFD;
	}

	avail = snd_compr_get_avail(stream);
	pr_debug("avail returned %ld\n", (unsigned long)avail);
	/* calculate how much we can write to buffer */
	if (avail > count)
		avail = count;

	if (stream->ops->copy)
		retval = stream->ops->copy(stream, buf, avail);
	else
		retval = snd_compr_write_data(stream, buf, avail);
	if (retval > 0)
		stream->runtime->total_bytes_available += retval;

	/* while initiating the stream, write should be called before START
	 * call, so in setup move state */
	if (stream->runtime->state == SNDRV_PCM_STATE_SETUP) {
		stream->runtime->state = SNDRV_PCM_STATE_PREPARED;
		pr_debug("stream prepared, Houston we are good to go\n");
	}

	mutex_unlock(&stream->device->lock);
	return retval;
}

Unknown