[PATCH v4 0/2] ucm: Automatically load the best config file based on the card long name

[PATCH v4 0/2] ucm: Automatically load the best config file based on the card long name

[mengdong.lin]

From: Mengdong Lin <mengdong.lin@linux.intel.com>

Intel DSP platform drivers are used by many different devices. For user
space to differentiate them, now ASoC provide API for machine drivers to
include the DMI info (vendor, product and board) in card long name. This
series will add UCM support for loading best device-specific configuration
based on the card long name.

Mengdong Lin (2):
  ucm: Load device-specific configuration file based on the card long
    name
  ucm: Add command 'get _file' to get the config file name of the opened
    card

History:
v2: Request the device-specific file name to match the card long name,
    no long use automatic key word matching and scoring to avoid error
    and uncertainty. And add command to check the name of actually loaded
    configuration file.

v3: Fix num in strncpy of the long name, which should be
    MAX_CARD_LONG_NAME - 1, not MAX_CARD_LONG_NAME (80).


v4: No code change. Just update on comments because the kernel v4 patches
    add DMI product version to the card long name, and use "-" as
    the separator between DMI fields.

Mengdong Lin (2):
  ucm: Load device-specific configuration file based on the card long
    name
  ucm: Add command 'get _file' to get the config file name of the opened
    card

 include/use-case.h  |   1 +
 src/ucm/main.c      |  14 ++++++++
 src/ucm/parser.c    | 101 +++++++++++++++++++++++++++++++++++++++++++++++++---
 src/ucm/ucm_local.h |   3 ++
 4 files changed, 115 insertions(+), 4 deletions(-)

-- 
2.7.4

[PATCH v4 1/2] ucm: Load device-specific configuration file based on the card long name

[mengdong.lin]

From: Mengdong Lin <mengdong.lin@linux.intel.com>

Intel DSP platform drivers are used by many different devices. For user
space to differentiate them, ASoC machine drivers may use the DMI info
(vendor-product-version-board) as card long name. Possible card long names
are:
DellInc.-XPS139343-01-0310JH
ASUSTeKCOMPUTERINC.-T100TA-1.0-T100TA
Circuitco-MinnowboardMaxD0PLATFORM-D0-MinnowBoardMAX
...

And user space can define configuration files like longname\longname.conf
for a specific device.

When being asked to load configuration file of a card, UCM will try to
find the card in the local machine and get its long name. If the card
long name is available, try to load the file longname\longname.conf to
get the best device-specific configuration; if this file is not available,
fall back to load the default configuration file shortname\shortname.conf
as before.

This update is backward compatible, because if ASoC machine drivers don't
explicity use DMI or other means to set the card long name, ASoC core
will use the card short name as the long name. And so UCM will load the
config file that matches both the card short name and the long name.

Signed-off-by: Mengdong Lin <mengdong.lin@linux.intel.com>

diff --git a/src/ucm/parser.c b/src/ucm/parser.c
index c98373a..14ee33f 100644
--- a/src/ucm/parser.c
+++ b/src/ucm/parser.c
@@ -55,6 +55,9 @@ static const char * const component_dir[] = {
 	NULL,		/* terminator */
 };
 
+static int filename_filter(const struct dirent *dirent);
+static int is_component_directory(const char *dir);
+
 static int parse_sequence(snd_use_case_mgr_t *uc_mgr,
 			  struct list_head *base,
 			  snd_config_t *cfg);
@@ -1328,6 +1331,66 @@ static int parse_master_file(snd_use_case_mgr_t *uc_mgr, snd_config_t *cfg)
 	return 0;
 }
 
+/* find the card in the local machine and store the card long name */
+static int get_card_long_name(snd_use_case_mgr_t *mgr)
+{
+	const char *card_name = mgr->card_name;
+	snd_ctl_t *handle;
+	int card, err;
+	snd_ctl_card_info_t *info;
+	const char *_name, *_long_name;
+
+	snd_ctl_card_info_alloca(&info);
+
+	card = -1;
+	if (snd_card_next(&card) < 0 || card < 0) {
+		uc_error("no soundcards found...");
+		return -1;
+	}
+
+	while (card >= 0) {
+		char name[32];
+
+		sprintf(name, "hw:%d", card);
+		err = snd_ctl_open(&handle, name, 0);
+		if (err < 0) {
+			uc_error("control open (%i): %s", card,
+				 snd_strerror(err));
+			goto next_card;
+		}
+
+		err = snd_ctl_card_info(handle, info);
+		if (err < 0) {
+			uc_error("control hardware info (%i): %s", card,
+				 snd_strerror(err));
+			snd_ctl_close(handle);
+			goto next_card;
+		}
+
+		/* Find the local card by comparing the given name with the
+		 * card name and long name. User may open a card by its long
+		 * name, so the given card name may be a long name.
+		 */
+		_name = snd_ctl_card_info_get_name(info);
+		_long_name = snd_ctl_card_info_get_longname(info);
+		if (!strncmp(card_name, _name, MAX_CARD_LONG_NAME)
+		    || !strncmp(card_name, _long_name, MAX_CARD_LONG_NAME)) {
+			strncpy(mgr->card_long_name, _long_name,
+				MAX_CARD_LONG_NAME - 1);
+			snd_ctl_close(handle);
+			return 0;
+		}
+
+		snd_ctl_close(handle);
+next_card:
+		if (snd_card_next(&card) < 0) {
+			uc_error("snd_card_next");
+			break;
+		}
+	}
+
+	return -1;
+}
 static int load_master_config(const char *card_name, snd_config_t **cfg)
 {
 	char filename[MAX_FILE];
@@ -1349,15 +1412,45 @@ static int load_master_config(const char *card_name, snd_config_t **cfg)
 	return 0;
 }
 
-/* load master use case file for sound card */
+/* load master use case file for sound card
+ *
+ * The same ASoC machine driver can be shared by many different devices.
+ * For user space to differentiate them and get the best device-specific
+ * configuration, ASoC machine drivers may use the DMI info
+ * (vendor.product.board) as the card long name. And user space can define
+ * configuration files like longname\longname.conf for a specific device.
+ *
+ * This function will try to find the card in the local machine and get its
+ * long name, then load the file longname\longname.conf to get the best
+ * device-specific configuration. If the card is not found in the local
+ * machine or the device-specific file is not available, fall back to load
+ * the default configuration file name\name.conf.
+ */
 int uc_mgr_import_master_config(snd_use_case_mgr_t *uc_mgr)
 {
 	snd_config_t *cfg;
 	int err;
 
-	err = load_master_config(uc_mgr->card_name, &cfg);
-	if (err < 0)
-		return err;
+	err = get_card_long_name(uc_mgr);
+	if (err == 0)	/* load file that maches the card long name */
+		err = load_master_config(uc_mgr->card_long_name, &cfg);
+
+	if (err == 0) {
+		/* got device-specific file that matches the card long name */
+		strncpy(uc_mgr->conf_file_name, uc_mgr->card_long_name,
+			MAX_CARD_LONG_NAME - 1);
+	} else {
+		/* Fall back to the file that maches the given card name,
+		 * either short name or long name (users may open a card by
+		 * its name or long name).
+		 */
+		err = load_master_config(uc_mgr->card_name, &cfg);
+		if (err < 0)
+			return err;
+		strncpy(uc_mgr->conf_file_name, uc_mgr->card_name,
+			MAX_CARD_LONG_NAME - 1);
+	}
+
 	err = parse_master_file(uc_mgr, cfg);
 	snd_config_delete(cfg);
 	if (err < 0)
diff --git a/src/ucm/ucm_local.h b/src/ucm/ucm_local.h
index 6d3302f..299a5b9 100644
--- a/src/ucm/ucm_local.h
+++ b/src/ucm/ucm_local.h
@@ -41,6 +41,7 @@
 #include "use-case.h"
 
 #define MAX_FILE		256
+#define MAX_CARD_LONG_NAME	80
 #define ALSA_USE_CASE_DIR	ALSA_CONFIG_DIR "/ucm"
 
 #define SEQUENCE_ELEMENT_TYPE_CDEV	1
@@ -190,6 +191,8 @@ struct use_case_verb {
  */
 struct snd_use_case_mgr {
 	char *card_name;
+	char card_long_name[MAX_CARD_LONG_NAME];
+	char conf_file_name[MAX_CARD_LONG_NAME];
 	char *comment;
 
 	/* use case verb, devices and modifier configs parsed from files */
-- 
2.7.4

Re: [PATCH v4 1/2] ucm: Load device-specific configuration file based on the card long name

[Takashi Iwai]

On Sat, 14 Jan 2017 09:23:55 +0100,
mengdong.lin@linux.intel.com wrote:
> 
> From: Mengdong Lin <mengdong.lin@linux.intel.com>
> 
> Intel DSP platform drivers are used by many different devices. For user
> space to differentiate them, ASoC machine drivers may use the DMI info
> (vendor-product-version-board) as card long name. Possible card long names
> are:
> DellInc.-XPS139343-01-0310JH
> ASUSTeKCOMPUTERINC.-T100TA-1.0-T100TA
> Circuitco-MinnowboardMaxD0PLATFORM-D0-MinnowBoardMAX
> ...
> 
> And user space can define configuration files like longname\longname.conf
> for a specific device.

Do you mean a file name containing a backslash?
I didn't find the relevant code in your patch...


> When being asked to load configuration file of a card, UCM will try to
> find the card in the local machine and get its long name. If the card
> long name is available, try to load the file longname\longname.conf to
> get the best device-specific configuration; if this file is not available,
> fall back to load the default configuration file shortname\shortname.conf
> as before.
> 
> This update is backward compatible, because if ASoC machine drivers don't
> explicity use DMI or other means to set the card long name, ASoC core
> will use the card short name as the long name. And so UCM will load the
> config file that matches both the card short name and the long name.
> 
> Signed-off-by: Mengdong Lin <mengdong.lin@linux.intel.com>
> 
> diff --git a/src/ucm/parser.c b/src/ucm/parser.c
> index c98373a..14ee33f 100644
> --- a/src/ucm/parser.c
> +++ b/src/ucm/parser.c
> @@ -55,6 +55,9 @@ static const char * const component_dir[] = {
>  	NULL,		/* terminator */
>  };
>  
> +static int filename_filter(const struct dirent *dirent);
> +static int is_component_directory(const char *dir);
> +
>  static int parse_sequence(snd_use_case_mgr_t *uc_mgr,
>  			  struct list_head *base,
>  			  snd_config_t *cfg);
> @@ -1328,6 +1331,66 @@ static int parse_master_file(snd_use_case_mgr_t *uc_mgr, snd_config_t *cfg)
>  	return 0;
>  }
>  
> +/* find the card in the local machine and store the card long name */
> +static int get_card_long_name(snd_use_case_mgr_t *mgr)
> +{
> +	const char *card_name = mgr->card_name;
> +	snd_ctl_t *handle;
> +	int card, err;
> +	snd_ctl_card_info_t *info;
> +	const char *_name, *_long_name;
> +
> +	snd_ctl_card_info_alloca(&info);
> +
> +	card = -1;
> +	if (snd_card_next(&card) < 0 || card < 0) {
> +		uc_error("no soundcards found...");
> +		return -1;
> +	}
> +
> +	while (card >= 0) {
> +		char name[32];
> +
> +		sprintf(name, "hw:%d", card);
> +		err = snd_ctl_open(&handle, name, 0);
> +		if (err < 0) {
> +			uc_error("control open (%i): %s", card,
> +				 snd_strerror(err));
> +			goto next_card;
> +		}
> +
> +		err = snd_ctl_card_info(handle, info);
> +		if (err < 0) {
> +			uc_error("control hardware info (%i): %s", card,
> +				 snd_strerror(err));
> +			snd_ctl_close(handle);
> +			goto next_card;
> +		}
> +
> +		/* Find the local card by comparing the given name with the
> +		 * card name and long name. User may open a card by its long
> +		 * name, so the given card name may be a long name.
> +		 */
> +		_name = snd_ctl_card_info_get_name(info);
> +		_long_name = snd_ctl_card_info_get_longname(info);
> +		if (!strncmp(card_name, _name, MAX_CARD_LONG_NAME)
> +		    || !strncmp(card_name, _long_name, MAX_CARD_LONG_NAME)) {
> +			strncpy(mgr->card_long_name, _long_name,
> +				MAX_CARD_LONG_NAME - 1);

It's safer to assure the NUL-terminated string in mgr->card_name &
co.  Then the above strncmp() can be a simple strcmp().


thanks,

Takashi

> +			snd_ctl_close(handle);
> +			return 0;
> +		}
> +
> +		snd_ctl_close(handle);
> +next_card:
> +		if (snd_card_next(&card) < 0) {
> +			uc_error("snd_card_next");
> +			break;
> +		}
> +	}
> +
> +	return -1;
> +}
>  static int load_master_config(const char *card_name, snd_config_t **cfg)
>  {
>  	char filename[MAX_FILE];
> @@ -1349,15 +1412,45 @@ static int load_master_config(const char *card_name, snd_config_t **cfg)
>  	return 0;
>  }
>  
> -/* load master use case file for sound card */
> +/* load master use case file for sound card
> + *
> + * The same ASoC machine driver can be shared by many different devices.
> + * For user space to differentiate them and get the best device-specific
> + * configuration, ASoC machine drivers may use the DMI info
> + * (vendor.product.board) as the card long name. And user space can define
> + * configuration files like longname\longname.conf for a specific device.
> + *
> + * This function will try to find the card in the local machine and get its
> + * long name, then load the file longname\longname.conf to get the best
> + * device-specific configuration. If the card is not found in the local
> + * machine or the device-specific file is not available, fall back to load
> + * the default configuration file name\name.conf.
> + */
>  int uc_mgr_import_master_config(snd_use_case_mgr_t *uc_mgr)
>  {
>  	snd_config_t *cfg;
>  	int err;
>  
> -	err = load_master_config(uc_mgr->card_name, &cfg);
> -	if (err < 0)
> -		return err;
> +	err = get_card_long_name(uc_mgr);
> +	if (err == 0)	/* load file that maches the card long name */
> +		err = load_master_config(uc_mgr->card_long_name, &cfg);
> +
> +	if (err == 0) {
> +		/* got device-specific file that matches the card long name */
> +		strncpy(uc_mgr->conf_file_name, uc_mgr->card_long_name,
> +			MAX_CARD_LONG_NAME - 1);
> +	} else {
> +		/* Fall back to the file that maches the given card name,
> +		 * either short name or long name (users may open a card by
> +		 * its name or long name).
> +		 */
> +		err = load_master_config(uc_mgr->card_name, &cfg);
> +		if (err < 0)
> +			return err;
> +		strncpy(uc_mgr->conf_file_name, uc_mgr->card_name,
> +			MAX_CARD_LONG_NAME - 1);
> +	}
> +
>  	err = parse_master_file(uc_mgr, cfg);
>  	snd_config_delete(cfg);
>  	if (err < 0)
> diff --git a/src/ucm/ucm_local.h b/src/ucm/ucm_local.h
> index 6d3302f..299a5b9 100644
> --- a/src/ucm/ucm_local.h
> +++ b/src/ucm/ucm_local.h
> @@ -41,6 +41,7 @@
>  #include "use-case.h"
>  
>  #define MAX_FILE		256
> +#define MAX_CARD_LONG_NAME	80
>  #define ALSA_USE_CASE_DIR	ALSA_CONFIG_DIR "/ucm"
>  
>  #define SEQUENCE_ELEMENT_TYPE_CDEV	1
> @@ -190,6 +191,8 @@ struct use_case_verb {
>   */
>  struct snd_use_case_mgr {
>  	char *card_name;
> +	char card_long_name[MAX_CARD_LONG_NAME];
> +	char conf_file_name[MAX_CARD_LONG_NAME];
>  	char *comment;
>  
>  	/* use case verb, devices and modifier configs parsed from files */
> -- 
> 2.7.4
> 

Re: [PATCH v4 1/2] ucm: Load device-specific configuration file based on the card long name

[Lin, Mengdong]

> -----Original Message-----
> From: Takashi Iwai [mailto:tiwai@suse.de]
> Sent: Sunday, January 15, 2017 4:25 PM
> 
> On Sat, 14 Jan 2017 09:23:55 +0100,
> mengdong.lin@linux.intel.com wrote:
> >
> > From: Mengdong Lin <mengdong.lin@linux.intel.com>
> >
> > Intel DSP platform drivers are used by many different devices. For
> > user space to differentiate them, ASoC machine drivers may use the DMI
> > info
> > (vendor-product-version-board) as card long name. Possible card long
> > names
> > are:
> > DellInc.-XPS139343-01-0310JH
> > ASUSTeKCOMPUTERINC.-T100TA-1.0-T100TA
> > Circuitco-MinnowboardMaxD0PLATFORM-D0-MinnowBoardMAX
> > ...
> >
> > And user space can define configuration files like
> > longname\longname.conf for a specific device.
> 
> Do you mean a file name containing a backslash?
> I didn't find the relevant code in your patch...

No, the file name doesn't contain a backslash. It means we're using the card long name as both the directory name that contains the UCM config file and the name of the config file itself.
E.g. for the laptop Dell XPS 13, UCM will try to find a directory "DellInc.-XPS139343-01-0310JH", and then find the file " DellInc.-XPS139343-01-0310JH.conf" under the directory. If it cannot find the this file, it will fall back to open file "broadwell-rt286.conf" under directory "broadwell-rt286".

Sorry, I didn't give a clear explanation here. I'll revise the comments.

[snip]
 
> > +/* find the card in the local machine and store the card long name */
> > +static int get_card_long_name(snd_use_case_mgr_t *mgr) {
> > +	const char *card_name = mgr->card_name;
> > +	snd_ctl_t *handle;
> > +	int card, err;
> > +	snd_ctl_card_info_t *info;
> > +	const char *_name, *_long_name;
> > +
> > +	snd_ctl_card_info_alloca(&info);
> > +
> > +	card = -1;
> > +	if (snd_card_next(&card) < 0 || card < 0) {
> > +		uc_error("no soundcards found...");
> > +		return -1;
> > +	}
> > +
> > +	while (card >= 0) {
> > +		char name[32];
> > +
> > +		sprintf(name, "hw:%d", card);
> > +		err = snd_ctl_open(&handle, name, 0);
> > +		if (err < 0) {
> > +			uc_error("control open (%i): %s", card,
> > +				 snd_strerror(err));
> > +			goto next_card;
> > +		}
> > +
> > +		err = snd_ctl_card_info(handle, info);
> > +		if (err < 0) {
> > +			uc_error("control hardware info (%i): %s", card,
> > +				 snd_strerror(err));
> > +			snd_ctl_close(handle);
> > +			goto next_card;
> > +		}
> > +
> > +		/* Find the local card by comparing the given name with the
> > +		 * card name and long name. User may open a card by its
> long
> > +		 * name, so the given card name may be a long name.
> > +		 */
> > +		_name = snd_ctl_card_info_get_name(info);
> > +		_long_name = snd_ctl_card_info_get_longname(info);
> > +		if (!strncmp(card_name, _name, MAX_CARD_LONG_NAME)
> > +		    || !strncmp(card_name, _long_name,
> MAX_CARD_LONG_NAME)) {
> > +			strncpy(mgr->card_long_name, _long_name,
> > +				MAX_CARD_LONG_NAME - 1);
> 
> It's safer to assure the NUL-terminated string in mgr->card_name & co.  Then
> the above strncmp() can be a simple strcmp().

Okay. I'll add check  and assure this when receiving the mgr->card_name from the application.

Thanks
Mengdong

Re: [PATCH v4 1/2] ucm: Load device-specific configuration file based on the card long name

[Takashi Iwai]

On Sun, 15 Jan 2017 11:01:15 +0100,
Lin, Mengdong wrote:
> 
> > -----Original Message-----
> > From: Takashi Iwai [mailto:tiwai@suse.de]
> > Sent: Sunday, January 15, 2017 4:25 PM
> > 
> > On Sat, 14 Jan 2017 09:23:55 +0100,
> > mengdong.lin@linux.intel.com wrote:
> > >
> > > From: Mengdong Lin <mengdong.lin@linux.intel.com>
> > >
> > > Intel DSP platform drivers are used by many different devices. For
> > > user space to differentiate them, ASoC machine drivers may use the DMI
> > > info
> > > (vendor-product-version-board) as card long name. Possible card long
> > > names
> > > are:
> > > DellInc.-XPS139343-01-0310JH
> > > ASUSTeKCOMPUTERINC.-T100TA-1.0-T100TA
> > > Circuitco-MinnowboardMaxD0PLATFORM-D0-MinnowBoardMAX
> > > ...
> > >
> > > And user space can define configuration files like
> > > longname\longname.conf for a specific device.
> > 
> > Do you mean a file name containing a backslash?
> > I didn't find the relevant code in your patch...
> 
> No, the file name doesn't contain a backslash. It means we're using the card long name as both the directory name that contains the UCM config file and the name of the config file itself.
> E.g. for the laptop Dell XPS 13, UCM will try to find a directory "DellInc.-XPS139343-01-0310JH", and then find the file " DellInc.-XPS139343-01-0310JH.conf" under the directory. If it cannot find the this file, it will fall back to open file "broadwell-rt286.conf" under directory "broadwell-rt286".

Ah, a backslash as on DOS.  Use a slash for Linux instead :)


Takashi

Re: [PATCH v4 1/2] ucm: Load device-specific configuration file based on the card long name

[Lin, Mengdong]

> -----Original Message-----
> From: Takashi Iwai [mailto:tiwai@suse.de]
> Sent: Monday, January 16, 2017 6:41 PM
> To: Lin, Mengdong <mengdong.lin@intel.com>
> Cc: mengdong.lin@linux.intel.com; alsa-devel@alsa-project.org;
> liam.r.girdwood@linux.intel.com
> Subject: Re: [PATCH v4 1/2] ucm: Load device-specific configuration file based
> on the card long name
> 
> On Sun, 15 Jan 2017 11:01:15 +0100,
> Lin, Mengdong wrote:
> >
> > > -----Original Message-----
> > > From: Takashi Iwai [mailto:tiwai@suse.de]
> > > Sent: Sunday, January 15, 2017 4:25 PM
> > >
> > > On Sat, 14 Jan 2017 09:23:55 +0100,
> > > mengdong.lin@linux.intel.com wrote:
> > > >
> > > > From: Mengdong Lin <mengdong.lin@linux.intel.com>
> > > >
> > > > Intel DSP platform drivers are used by many different devices. For
> > > > user space to differentiate them, ASoC machine drivers may use the
> > > > DMI info
> > > > (vendor-product-version-board) as card long name. Possible card
> > > > long names
> > > > are:
> > > > DellInc.-XPS139343-01-0310JH
> > > > ASUSTeKCOMPUTERINC.-T100TA-1.0-T100TA
> > > > Circuitco-MinnowboardMaxD0PLATFORM-D0-MinnowBoardMAX
> > > > ...
> > > >
> > > > And user space can define configuration files like
> > > > longname\longname.conf for a specific device.
> > >
> > > Do you mean a file name containing a backslash?
> > > I didn't find the relevant code in your patch...
> >
> > No, the file name doesn't contain a backslash. It means we're using the
> card long name as both the directory name that contains the UCM config file
> and the name of the config file itself.
> > E.g. for the laptop Dell XPS 13, UCM will try to find a directory "DellInc.-
> XPS139343-01-0310JH", and then find the file " DellInc.-XPS139343-01-
> 0310JH.conf" under the directory. If it cannot find the this file, it will fall back
> to open file "broadwell-rt286.conf" under directory "broadwell-rt286".
> 
> Ah, a backslash as on DOS.  Use a slash for Linux instead :)
> 
> 
> Takashi

Sorry, I fixed this in v6. Now the kernel side patches have been applied to ASoC so there is no dependency now.

Thanks
Mengdong

[PATCH v4 2/2] ucm: Add command 'get _file' to get the config file name of the opened card

[mengdong.lin]

From: Mengdong Lin <mengdong.lin@linux.intel.com>

After opening a card, this command can show the name of the actually
loaded configuration file, either matches the card name or card long name.
So developers can check if there is a device-sepcific configuration file
available for a given card.

Signed-off-by: Mengdong Lin <mengdong.lin@linux.intel.com>

diff --git a/include/use-case.h b/include/use-case.h
index 8911645..ae22bde 100644
--- a/include/use-case.h
+++ b/include/use-case.h
@@ -230,6 +230,7 @@ int snd_use_case_get_list(snd_use_case_mgr_t *uc_mgr,
  * Known identifiers:
  *   - NULL 		- return current card
  *   - _verb		- return current verb
+ *   - _file		- return configuration file loaded for current card
  *
  *   - [=]{NAME}[/[{modifier}|{/device}][/{verb}]]
  *                      - value identifier {NAME}
diff --git a/src/ucm/main.c b/src/ucm/main.c
index 38a5e81..2d33886 100644
--- a/src/ucm/main.c
+++ b/src/ucm/main.c
@@ -1528,6 +1528,20 @@ int snd_use_case_get(snd_use_case_mgr_t *uc_mgr,
                         goto __end;
                 }
 	        err = 0;
+	} else if (strcmp(identifier, "_file") == 0) {
+		/* get the conf file name of the opened card */
+		if ((uc_mgr->card_name == NULL)
+		    || (uc_mgr->conf_file_name[0] == '\0')) {
+			err = -ENOENT;
+			goto __end;
+		}
+		*value = strndup(uc_mgr->conf_file_name, MAX_FILE);
+		if (*value == NULL) {
+			err = -ENOMEM;
+			goto __end;
+		}
+		err = 0;
+
 	} else if (identifier[0] == '_') {
 		err = -ENOENT;
 		goto __end;
-- 
2.7.4