[pulseaudio-discuss] [PATCH 1/3] alsa-util: Add a function to read ELD info

[Tanu Kaskinen]

On Fri, 2013-02-15 at 13:42 +0100, David Henningsson wrote:
> Currently, this function only reads the monitor name, but could
> be extended to read e g supported formats as well.
> 
> Signed-off-by: David Henningsson <david.henningsson at canonical.com>
> ---
>  src/modules/alsa/alsa-util.c |   55 ++++++++++++++++++++++++++++++++++++++++++
>  src/modules/alsa/alsa-util.h |    7 ++++++
>  2 files changed, 62 insertions(+)
> 
> diff --git a/src/modules/alsa/alsa-util.c b/src/modules/alsa/alsa-util.c
> index 114ab27..7cc9492 100644
> --- a/src/modules/alsa/alsa-util.c
> +++ b/src/modules/alsa/alsa-util.c
> @@ -1574,3 +1574,58 @@ snd_mixer_t *pa_alsa_open_mixer_for_pcm(snd_pcm_t *pcm, char **ctl_device, snd_h
>      snd_mixer_close(m);
>      return NULL;
>  }
> +
> +bool pa_alsa_get_hdmi_eld(snd_hctl_t *hctl, int device, pa_hdmi_eld_t *eld) {
> +

The function could start with a comment containing a link to a
specification of the ELD data format. I didn't manage to find such
document (it doesn't help that I couldn't even figure out what the
acronym stands for), so I can't check whether the parsing code is
correct.

> +    int err;
> +    snd_ctl_elem_id_t *id;
> +    snd_hctl_elem_t *elem;
> +    snd_ctl_elem_info_t *info;
> +    snd_ctl_elem_value_t *value;
> +    unsigned char *elddata;

Usually uint8_t is used as the type for binary data.

> +    unsigned int eldsize, mnl;
> +
> +    pa_assert(eld != NULL);
> +
> +    /* See if we can find the ELD control */
> +    snd_ctl_elem_id_alloca(&id);

This allocates memory, right? It's never freed.

> +    snd_ctl_elem_id_clear(id);
> +    snd_ctl_elem_id_set_interface(id, SND_CTL_ELEM_IFACE_PCM);
> +    snd_ctl_elem_id_set_name(id, "ELD");
> +    snd_ctl_elem_id_set_device(id, device);
> +
> +    elem = snd_hctl_find_elem(hctl, id);
> +    if (elem == NULL) {
> +        pa_log_debug("No ELD info control found (for device=%d)", device);
> +        return false;
> +    }
> +
> +    /* Does it have any contents? */
> +    snd_ctl_elem_info_alloca(&info);
> +    snd_ctl_elem_value_alloca(&value);

These are not freed either.

> +    if ((err = snd_hctl_elem_info(elem, info)) < 0 ||
> +       (err = snd_hctl_elem_read(elem, value)) < 0) {
> +        pa_log_warn("Accessing ELD control failed with error %s", snd_strerror(err));
> +        return false;
> +    }
> +
> +    eldsize = snd_ctl_elem_info_get_count(info);
> +    elddata = (unsigned char *) snd_ctl_elem_value_get_bytes(value);
> +    if (eldsize < 20 || eldsize > 256 || elddata == NULL) {
> +        pa_log_debug("ELD info empty (for device=%d)", device);

The error message is not very good if eldsize > 0.

> +        return false;
> +    }
> +
> +    /* Try to fetch monitor name */
> +    mnl = elddata[4] & 0x1f;
> +    if (mnl == 0 || mnl > 16 || 20 + mnl > eldsize) {
> +        pa_log_debug("No monitor name in ELD info (for device=%d)", device);
> +        mnl = 0;
> +    }
> +    memcpy(eld->monitor_name, &elddata[20], mnl);
> +    eld->monitor_name[mnl] = '\0';
> +    if (mnl)
> +        pa_log_debug("Monitor name in ELD info is '%s' (for device=%d)", eld->monitor_name, device);
> +
> +    return true;
> +}
> diff --git a/src/modules/alsa/alsa-util.h b/src/modules/alsa/alsa-util.h
> index 1326e64..db6f638 100644
> --- a/src/modules/alsa/alsa-util.h
> +++ b/src/modules/alsa/alsa-util.h
> @@ -146,4 +146,11 @@ snd_hctl_elem_t* pa_alsa_find_jack(snd_hctl_t *hctl, const char* jack_name);
>  
>  snd_mixer_t *pa_alsa_open_mixer(int alsa_card_index, char **ctl_device, snd_hctl_t **hctl);
>  
> +typedef struct pa_hdmi_eld_t pa_hdmi_eld_t;

Structs shouldn't have the _t suffix.

> +struct pa_hdmi_eld_t {
> +    char monitor_name[17];

Is the parsed ELD field only set for monitors, and not for any other
type of HDMI hardware?

-- 
Tanu