[pulseaudio-discuss] [PATCH 06/11] Introduce pa_device_prototype

[David Henningsson]

On 11/24/2013 06:58 AM, Tanu Kaskinen wrote:
> A "device prototype" is an object that allows referencing potential
> devices, i.e. sinks and sources that don't exist. 

I think this needs further explanation.

First; if the sinks and sources don't exist, it seems a bit strange to
represent them as sinks and sources...? Maybe pointers to sink_new_data
and source_new_data would make more sense, conceptually? Not sure.

> A card usually has
> profiles that don't contain all devices that the card can create. The
> card knows about all potential sinks and sources, and it would be
> useful to make this information available also outside the card.
> 
> In my case I need it for implementing a "rescue policy" for profile
> switch cases in module-skoa-router. The module shouldn't rescue
> streams that are connected to devices that are not actually going to
> be removed, because this causes glitches in the audio. Therefore, the
> module needs to know before the profile switch happens whether a
> device is going to be removed as a part of the profile switch.
> 
> The prototype has pointers to a sink and source. The prototype has
> an implicit direction, and if it's an output device prototype, then
> the source pointer must always be NULL (likewise for the sink pointer
> for input device prototypes). The sink/source pointer is non-NULL
> when a sink/source exists that is represented by the device prototype.

The suggestion to store this prototypes as something that looks like a
set of one source and one sink looks strange to me. What if you had two
hashmaps, one for sinks and one for sources, is this object at all
needed then?

Also, who owns the actual device prototype object, is it the card
profile or the source/sink?

Finally, this looks like a very small object and unlikely to become
large any time soon. It does not need its own .c/.h files - it would fit
fine inside e g card.h.

> 
> This patch only adds the device prototype implementation, the
> prototypes aren't used yet.
> ---
>  src/Makefile.am                  |  1 +
>  src/pulsecore/device-prototype.c | 52 ++++++++++++++++++++++++++++++++++++++++
>  src/pulsecore/device-prototype.h | 40 +++++++++++++++++++++++++++++++
>  3 files changed, 93 insertions(+)
>  create mode 100644 src/pulsecore/device-prototype.c
>  create mode 100644 src/pulsecore/device-prototype.h
> 
> diff --git a/src/Makefile.am b/src/Makefile.am
> index e024d9a..b92b613 100644
> --- a/src/Makefile.am
> +++ b/src/Makefile.am
> @@ -875,6 +875,7 @@ libpulsecore_ at PA_MAJORMINOR@_la_SOURCES = \
>  		pulsecore/core-scache.c pulsecore/core-scache.h \
>  		pulsecore/core-subscribe.c pulsecore/core-subscribe.h \
>  		pulsecore/core.c pulsecore/core.h \
> +		pulsecore/device-prototype.c pulsecore/device-prototype.h \
>  		pulsecore/fdsem.c pulsecore/fdsem.h \
>  		pulsecore/hook-list.c pulsecore/hook-list.h \
>  		pulsecore/ltdl-helper.c pulsecore/ltdl-helper.h \
> diff --git a/src/pulsecore/device-prototype.c b/src/pulsecore/device-prototype.c
> new file mode 100644
> index 0000000..20cce8f
> --- /dev/null
> +++ b/src/pulsecore/device-prototype.c
> @@ -0,0 +1,52 @@
> +/***
> +  This file is part of PulseAudio.
> +
> +  Copyright 2013 Intel Corporation
> +
> +  PulseAudio is free software; you can redistribute it and/or modify
> +  it under the terms of the GNU Lesser General Public License as published
> +  by the Free Software Foundation; either version 2.1 of the License,
> +  or (at your option) any later version.
> +
> +  PulseAudio is distributed in the hope that it will be useful, but
> +  WITHOUT ANY WARRANTY; without even the implied warranty of
> +  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> +  General Public License for more details.
> +
> +  You should have received a copy of the GNU Lesser General Public License
> +  along with PulseAudio; if not, write to the Free Software
> +  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
> +  USA.
> +***/
> +
> +#ifdef HAVE_CONFIG_H
> +#include <config.h>
> +#endif
> +
> +#include "device-prototype.h"
> +
> +pa_device_prototype *pa_device_prototype_new(void) {
> +    pa_device_prototype *prototype;
> +
> +    prototype = pa_xnew0(pa_device_prototype, 1);
> +
> +    return prototype;
> +}
> +
> +void pa_device_prototype_free(pa_device_prototype *prototype) {
> +    pa_assert(prototype);
> +
> +    pa_xfree(prototype);
> +}
> +
> +void pa_device_prototype_set_sink(pa_device_prototype *prototype, pa_sink *sink) {
> +    pa_assert(prototype);
> +
> +    prototype->sink = sink;
> +}
> +
> +void pa_device_prototype_set_source(pa_device_prototype *prototype, pa_source *source) {
> +    pa_assert(prototype);
> +
> +    prototype->source = source;
> +}
> diff --git a/src/pulsecore/device-prototype.h b/src/pulsecore/device-prototype.h
> new file mode 100644
> index 0000000..2087152
> --- /dev/null
> +++ b/src/pulsecore/device-prototype.h
> @@ -0,0 +1,40 @@
> +#ifndef foodeviceprototypehfoo
> +#define foodeviceprototypehfoo
> +
> +/***
> +  This file is part of PulseAudio.
> +
> +  Copyright 2013 Intel Corporation
> +
> +  PulseAudio is free software; you can redistribute it and/or modify
> +  it under the terms of the GNU Lesser General Public License as published
> +  by the Free Software Foundation; either version 2.1 of the License,
> +  or (at your option) any later version.
> +
> +  PulseAudio is distributed in the hope that it will be useful, but
> +  WITHOUT ANY WARRANTY; without even the implied warranty of
> +  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> +  General Public License for more details.
> +
> +  You should have received a copy of the GNU Lesser General Public License
> +  along with PulseAudio; if not, write to the Free Software
> +  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
> +  USA.
> +***/
> +
> +#include <pulsecore/source.h>
> +
> +typedef struct pa_device_prototype pa_device_prototype;
> +
> +struct pa_device_prototype {
> +    pa_sink *sink;
> +    pa_source *source;
> +};
> +
> +pa_device_prototype *pa_device_prototype_new(void);
> +void pa_device_prototype_free(pa_device_prototype *prototype);
> +
> +void pa_device_prototype_set_sink(pa_device_prototype *prototype, pa_sink *sink);
> +void pa_device_prototype_set_source(pa_device_prototype *prototype, pa_source *source);
> +
> +#endif
> 



-- 
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic