On Mon, 21 Mar 2016 09:37:54 +0100,
libin.yang@xxxxxxxxxxxxxxx wrote:
>
> From: Libin Yang <libin.yang@xxxxxxxxxxxxxxx>
>
> Add snd_hda_get_dev_select() and snd_hda_set_dev_select() functions
> for DP MST audio support.
>
> Signed-off-by: Libin Yang <libin.yang@xxxxxxxxxxxxxxx>
> ---
> sound/pci/hda/hda_codec.c | 83 ++++++++++++++++++++++++++++++++++++++++++++---
> sound/pci/hda/hda_codec.h | 3 ++
> 2 files changed, 82 insertions(+), 4 deletions(-)
>
> diff --git a/sound/pci/hda/hda_codec.c b/sound/pci/hda/hda_codec.c
> index d17e38e..db94a66 100644
> --- a/sound/pci/hda/hda_codec.c
> +++ b/sound/pci/hda/hda_codec.c
> @@ -325,9 +325,16 @@ int snd_hda_get_conn_index(struct hda_codec *codec, hda_nid_t mux,
> }
> EXPORT_SYMBOL_GPL(snd_hda_get_conn_index);
>
> -
> -/* return DEVLIST_LEN parameter of the given widget */
> -static unsigned int get_num_devices(struct hda_codec *codec, hda_nid_t nid)
> +/**
> + * snd_hda_get_num_devices - get DEVLIST_LEN parameter of the given widget
> + * @codec: the HDA codec
> + * @nid: NID of the pin to parse
> + *
> + * Get the device entry number on the given widget.
> + * This is a feature of DP MST audio. Each pin can
> + * have several device entries in it.
> + */
> +unsigned int snd_hda_get_num_devices(struct hda_codec *codec, hda_nid_t nid)
> {
> unsigned int wcaps = get_wcaps(codec, nid);
> unsigned int parm;
> @@ -341,6 +348,7 @@ static unsigned int get_num_devices(struct hda_codec *codec, hda_nid_t nid)
> parm = 0;
> return parm & AC_DEV_LIST_LEN_MASK;
> }
> +EXPORT_SYMBOL_GPL(snd_hda_get_num_devices);
>
> /**
> * snd_hda_get_devices - copy device list without cache
> @@ -358,7 +366,7 @@ int snd_hda_get_devices(struct hda_codec *codec, hda_nid_t nid,
> unsigned int parm;
> int i, dev_len, devices;
>
> - parm = get_num_devices(codec, nid);
> + parm = snd_hda_get_num_devices(codec, nid);
> if (!parm) /* not multi-stream capable */
> return 0;
>
> @@ -382,6 +390,73 @@ int snd_hda_get_devices(struct hda_codec *codec, hda_nid_t nid,
> return devices;
> }
>
> +/**
> + * snd_hda_get_dev_select - get device entry select on the pin
> + * @codec: the HDA codec
> + * @nid: NID of the pin to get device entry select
> + *
> + * Get the devcie entry select on the pin. Return the device entry
> + * id selected on the pin. Return 0 means the first device entry
> + * is selected or MST is not supported.
> + */
> +int snd_hda_get_dev_select(struct hda_codec *codec, hda_nid_t nid)
> +{
> + /* not support dp_mst will always return 0, using first dev_entry */
> + if (!codec->dp_mst)
> + return 0;
> +
> + return snd_hda_codec_read(codec, nid, 0, AC_VERB_GET_DEVICE_SEL, 0);
> +}
> +EXPORT_SYMBOL_GPL(snd_hda_get_dev_select);
> +
> +/**
> + * snd_hda_set_dev_select - set device entry select on the pin
> + * @codec: the HDA codec
> + * @nid: NID of the pin to set device entry select
> + * @dev_id: device entry id to be set
> + *
> + * Set the device entry select on the pin nid.
> + */
> +int snd_hda_set_dev_select(struct hda_codec *codec, hda_nid_t nid, int dev_id)
> +{
> + int ret, dev, num_devices;
> + unsigned long timeout;
> +
> + /* not support dp_mst will always return 0, using first dev_entry */
> + if (!codec->dp_mst)
> + return 0;
> +
> + /* AC_PAR_DEVLIST_LEN is 0 based. */
> + num_devices = snd_hda_get_num_devices(codec, nid);
> + /* If Device List Length is 0, the pin is not multi stream capable.
> + */
> + if (num_devices == 0)
> + return 0;
> +
> + /* Behavior of setting index being equal to or greater than
> + * Device List Length is not predictable
> + */
> + if (num_devices + 1 <= dev_id)
> + return 0;
Is this correct? Doesn't num_devices=1 mean that there is only a
single device? If dev_id=1 must be invalid, but the check above
passes. The standard form of such index check is like
if (dev_id >= num_devices)
error;
And this also leads to the question. Shouldn't we return an error if
an invalid dev_id is given?
> +
> + timeout = jiffies + msecs_to_jiffies(500);
> +
> + /* make sure the device entry selection takes effect */
> + do {
> + ret = snd_hda_codec_write(codec, nid, 0,
> + AC_VERB_SET_DEVICE_SEL, dev_id);
> + udelay(20);
> +
> + dev = snd_hda_get_dev_select(codec, nid);
> + if (dev == dev_id)
> + break;
> + msleep(20);
> + } while (time_before(jiffies, timeout));
Is this loop needed? Most verbs take effect immediately, and so far,
the only exception is the power state.
Takashi
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