[alsa-devel] [PATCH 05/39] firewire-lib: Add support for AMDTP in-stream and PCM capture

[Clemens Ladisch]

Takashi Sakamoto wrote:
> For capturing PCM, this commit adds the functionality to handle in-stream.
> This is also applied for dual-wire mode.

> +++ b/sound/firewire/amdtp.c
> @@ -200,16 +208,26 @@ void amdtp_stream_set_pcm_format(struct amdtp_stream *s,
> +		if (s->direction == AMDTP_OUT_STREAM) {
> +			if (s->dual_wire)
> +				s->transfer_samples = amdtp_write_s32_dualwire;
> +			else
> +				s->transfer_samples = amdtp_write_s32;
> +		} else if (s->dual_wire) {
> +			s->transfer_samples = amdtp_read_s32_dualwire;
> +		} else {
> +			s->transfer_samples = amdtp_read_s32;
> +		}

Please format the if/else branches in the same way.

> +static void handle_in_packet(struct amdtp_stream *s,
> ...
> +	/* ignore empty CIP packet or NO-DATA AMDTP packet */
> +	if ((payload_quadlets < 3) ||
> +	    (((cip_header[1] & CIP_FDF_MASK) >> CIP_FDF_SFC_SHIFT) ==
> +							AMDTP_FDF_NO_DATA))

(AMDTP_FDF_NO_DATA << CIP_FDF_SFC_SHIFT) would be a constant that could
be computed at compile time.

> +	/* check packet continuity */
> +	s->data_block_counter = (s->data_block_counter + data_blocks) & 0xff;
> +	if (s->data_block_counter != data_block_counter) {
> +		dev_info_ratelimited(&s->unit->device,
> +				     "Detect uncontinuity of CIP packets\n");
> +		s->data_block_counter = data_block_counter;
> +		return;

In practice, this error means that a packet was dropped.  I guess this
doesn't actually happen too often, but eventually, we should handle
this either by inserting some samples or by stopping the stream.


Regards,
Clemens