[alsa-devel] [PATCH v3] ALSA: usb-audio: Add support for Presonus Studio 1810c

Takashi Iwai tiwai at suse.de
Sat Feb 15 09:52:30 CET 2020


On Sat, 15 Feb 2020 02:23:35 +0100,
mickflemm at gmail.com wrote:
> 
> From: Nick Kossifidis <mickflemm at gmail.com>
> 
> This patch adds support for Presonus Studio 1810c, a usb interface
> that's UAC2 compliant with a few quirks and a few extra hw-specific
> controls. I've tested all 3 altsettings and the added switch
> controls and they work as expected.
> 
> More infos on the card:
> https://www.presonus.com/products/Studio-1810c
> 
> Note that this work is based on packet inspection with
> usbmon. I just wanted to get this card to work for using
> it on our open-source radio station:
> https://github.com/UoC-Radio
> 
> v2 address issues reported by Takashi:
> * Properly get/set enum type controls
> * Prevent race condition on switch_get/set
> * Various control naming changes
> * Various coding style fixes
> 
> v3 improve readability of sample rate filtering
> and some other minor changes.
> 
> Signed-off-by: Nick Kossifidis <mickflemm at gmail.com>

Thanks, applied now.

The only slight concern I found now is that the packet definition is
likely little-endian; i.e. you'd need to declare the fields like
__le32 instead of u32, and convert at each place via cpu_to_le32() &
co.

In anyway the patch was merged as-is, so please submit additional
fixes on top of this.


thanks,

Takashi

> ---
>  sound/usb/Makefile       |   1 +
>  sound/usb/format.c       |  37 +++
>  sound/usb/mixer_quirks.c |   5 +
>  sound/usb/mixer_s1810c.c | 595 +++++++++++++++++++++++++++++++++++++++
>  sound/usb/mixer_s1810c.h |   7 +
>  sound/usb/quirks.c       |  36 +++
>  6 files changed, 681 insertions(+)
>  create mode 100644 sound/usb/mixer_s1810c.c
>  create mode 100644 sound/usb/mixer_s1810c.h
> 
> diff --git a/sound/usb/Makefile b/sound/usb/Makefile
> index 78edd7d2f..56031026b 100644
> --- a/sound/usb/Makefile
> +++ b/sound/usb/Makefile
> @@ -13,6 +13,7 @@ snd-usb-audio-objs := 	card.o \
>  			mixer_scarlett.o \
>  			mixer_scarlett_gen2.o \
>  			mixer_us16x08.o \
> +			mixer_s1810c.o \
>  			pcm.o \
>  			power.o \
>  			proc.o \
> diff --git a/sound/usb/format.c b/sound/usb/format.c
> index d79db7130..462187953 100644
> --- a/sound/usb/format.c
> +++ b/sound/usb/format.c
> @@ -226,6 +226,36 @@ static int parse_audio_format_rates_v1(struct snd_usb_audio *chip, struct audiof
>  	return 0;
>  }
>  
> +
> +/*
> + * Presonus Studio 1810c supports a limited set of sampling
> + * rates per altsetting but reports the full set each time.
> + * If we don't filter out the unsupported rates and attempt
> + * to configure the card, it will hang refusing to do any
> + * further audio I/O until a hard reset is performed.
> + *
> + * The list of supported rates per altsetting (set of available
> + * I/O channels) is described in the owner's manual, section 2.2.
> + */
> +static bool s1810c_valid_sample_rate(struct audioformat *fp,
> +				     unsigned int rate)
> +{
> +	switch (fp->altsetting) {
> +	case 1:
> +		/* All ADAT ports available */
> +		return rate <= 48000;
> +	case 2:
> +		/* Half of ADAT ports available */
> +		return (rate == 88200 || rate == 96000);
> +	case 3:
> +		/* Analog I/O only (no S/PDIF nor ADAT) */
> +		return rate >= 176400;
> +	default:
> +		return false;
> +	}
> +	return false;
> +}
> +
>  /*
>   * Helper function to walk the array of sample rate triplets reported by
>   * the device. The problem is that we need to parse whole array first to
> @@ -262,6 +292,12 @@ static int parse_uac2_sample_rate_range(struct snd_usb_audio *chip,
>  		}
>  
>  		for (rate = min; rate <= max; rate += res) {
> +
> +			/* Filter out invalid rates on Presonus Studio 1810c */
> +			if (chip->usb_id == USB_ID(0x0194f, 0x010c) &&
> +			    !s1810c_valid_sample_rate(fp, rate))
> +				goto skip_rate;
> +
>  			if (fp->rate_table)
>  				fp->rate_table[nr_rates] = rate;
>  			if (!fp->rate_min || rate < fp->rate_min)
> @@ -276,6 +312,7 @@ static int parse_uac2_sample_rate_range(struct snd_usb_audio *chip,
>  				break;
>  			}
>  
> +skip_rate:
>  			/* avoid endless loop */
>  			if (res == 0)
>  				break;
> diff --git a/sound/usb/mixer_quirks.c b/sound/usb/mixer_quirks.c
> index 39e27ae6c..71e705fab 100644
> --- a/sound/usb/mixer_quirks.c
> +++ b/sound/usb/mixer_quirks.c
> @@ -34,6 +34,7 @@
>  #include "mixer_scarlett.h"
>  #include "mixer_scarlett_gen2.h"
>  #include "mixer_us16x08.h"
> +#include "mixer_s1810c.h"
>  #include "helper.h"
>  
>  struct std_mono_table {
> @@ -2277,6 +2278,10 @@ int snd_usb_mixer_apply_create_quirk(struct usb_mixer_interface *mixer)
>  	case USB_ID(0x2a39, 0x3fd4): /* RME */
>  		err = snd_rme_controls_create(mixer);
>  		break;
> +
> +	case USB_ID(0x0194f, 0x010c): /* Presonus Studio 1810c */
> +		err = snd_sc1810_init_mixer(mixer);
> +		break;
>  	}
>  
>  	return err;
> diff --git a/sound/usb/mixer_s1810c.c b/sound/usb/mixer_s1810c.c
> new file mode 100644
> index 000000000..8e2a05f80
> --- /dev/null
> +++ b/sound/usb/mixer_s1810c.c
> @@ -0,0 +1,595 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Presonus Studio 1810c driver for ALSA
> + * Copyright (C) 2019 Nick Kossifidis <mickflemm at gmail.com>
> + *
> + * Based on reverse engineering of the communication protocol
> + * between the windows driver / Univeral Control (UC) program
> + * and the device, through usbmon.
> + *
> + * For now this bypasses the mixer, with all channels split,
> + * so that the software can mix with greater flexibility.
> + * It also adds controls for the 4 buttons on the front of
> + * the device.
> + */
> +
> +#include <linux/usb.h>
> +#include <linux/usb/audio-v2.h>
> +#include <linux/slab.h>
> +#include <sound/core.h>
> +#include <sound/control.h>
> +
> +#include "usbaudio.h"
> +#include "mixer.h"
> +#include "mixer_quirks.h"
> +#include "helper.h"
> +#include "mixer_s1810c.h"
> +
> +#define SC1810C_CMD_REQ	160
> +#define SC1810C_CMD_REQTYPE \
> +	(USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT)
> +#define SC1810C_CMD_F1		0x50617269
> +#define SC1810C_CMD_F2		0x14
> +
> +/*
> + * DISCLAIMER: These are just guesses based on the
> + * dumps I got.
> + *
> + * It seems like a selects between
> + * device (0), mixer (0x64) and output (0x65)
> + *
> + * For mixer (0x64):
> + *  * b selects an input channel (see below).
> + *  * c selects an output channel pair (see below).
> + *  * d selects left (0) or right (1) of that pair.
> + *  * e 0-> disconnect, 0x01000000-> connect,
> + *	0x0109-> used for stereo-linking channels,
> + *	e is also used for setting volume levels
> + *	in which case b is also set so I guess
> + *	this way it is possible to set the volume
> + *	level from the specified input to the
> + *	specified output.
> + *
> + * IN Channels:
> + * 0  - 7  Mic/Inst/Line (Analog inputs)
> + * 8  - 9  S/PDIF
> + * 10 - 17 ADAT
> + * 18 - 35 DAW (Inputs from the host)
> + *
> + * OUT Channels (pairs):
> + * 0 -> Main out
> + * 1 -> Line1/2
> + * 2 -> Line3/4
> + * 3 -> S/PDIF
> + * 4 -> ADAT?
> + *
> + * For device (0):
> + *  * b and c are not used, at least not on the
> + *    dumps I got.
> + *  * d sets the control id to be modified
> + *    (see below).
> + *  * e sets the setting for that control.
> + *    (so for the switches I was interested
> + *    in it's 0/1)
> + *
> + * For output (0x65):
> + *   * b is the output channel (see above).
> + *   * c is zero.
> + *   * e I guess the same as with mixer except 0x0109
> + *	 which I didn't see in my dumps.
> + *
> + * The two fixed fields have the same values for
> + * mixer and output but a different set for device.
> + */
> +struct s1810c_ctl_packet {
> +	u32 a;
> +	u32 b;
> +	u32 fixed1;
> +	u32 fixed2;
> +	u32 c;
> +	u32 d;
> +	u32 e;
> +};
> +
> +#define SC1810C_CTL_LINE_SW	0
> +#define SC1810C_CTL_MUTE_SW	1
> +#define SC1810C_CTL_AB_SW	3
> +#define SC1810C_CTL_48V_SW	4
> +
> +#define SC1810C_SET_STATE_REQ	161
> +#define SC1810C_SET_STATE_REQTYPE SC1810C_CMD_REQTYPE
> +#define SC1810C_SET_STATE_F1	0x64656D73
> +#define SC1810C_SET_STATE_F2	0xF4
> +
> +#define SC1810C_GET_STATE_REQ	162
> +#define SC1810C_GET_STATE_REQTYPE \
> +	(USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN)
> +#define SC1810C_GET_STATE_F1	SC1810C_SET_STATE_F1
> +#define SC1810C_GET_STATE_F2	SC1810C_SET_STATE_F2
> +
> +#define SC1810C_STATE_F1_IDX	2
> +#define SC1810C_STATE_F2_IDX	3
> +
> +/*
> + * This packet includes mixer volumes and
> + * various other fields, it's an extended
> + * version of ctl_packet, with a and b
> + * being zero and different f1/f2.
> + */
> +struct s1810c_state_packet {
> +	u32 fields[63];
> +};
> +
> +#define SC1810C_STATE_48V_SW	58
> +#define SC1810C_STATE_LINE_SW	59
> +#define SC1810C_STATE_MUTE_SW	60
> +#define SC1810C_STATE_AB_SW	62
> +
> +struct s1810_mixer_state {
> +	uint16_t seqnum;
> +	struct mutex usb_mutex;
> +	struct mutex data_mutex;
> +};
> +
> +static int
> +snd_s1810c_send_ctl_packet(struct usb_device *dev, u32 a,
> +			   u32 b, u32 c, u32 d, u32 e)
> +{
> +	struct s1810c_ctl_packet pkt = { 0 };
> +	int ret = 0;
> +
> +	pkt.fixed1 = SC1810C_CMD_F1;
> +	pkt.fixed2 = SC1810C_CMD_F2;
> +
> +	pkt.a = a;
> +	pkt.b = b;
> +	pkt.c = c;
> +	pkt.d = d;
> +	/*
> +	 * Value for settings 0/1 for this
> +	 * output channel is always 0 (probably because
> +	 * there is no ADAT output on 1810c)
> +	 */
> +	pkt.e = (c == 4) ? 0 : e;
> +
> +	ret = snd_usb_ctl_msg(dev, usb_sndctrlpipe(dev, 0),
> +			      SC1810C_CMD_REQ,
> +			      SC1810C_CMD_REQTYPE, 0, 0, &pkt, sizeof(pkt));
> +	if (ret < 0) {
> +		dev_warn(&dev->dev, "could not send ctl packet\n");
> +		return ret;
> +	}
> +	return 0;
> +}
> +
> +/*
> + * When opening Universal Control the program periodicaly
> + * sends and receives state packets for syncinc state between
> + * the device and the host.
> + *
> + * Note that if we send only the request to get data back we'll
> + * get an error, we need to first send an empty state packet and
> + * then ask to receive a filled. Their seqnumbers must also match.
> + */
> +static int
> +snd_sc1810c_get_status_field(struct usb_device *dev,
> +			     u32 *field, int field_idx, uint16_t *seqnum)
> +{
> +	struct s1810c_state_packet pkt_out = { 0 };
> +	struct s1810c_state_packet pkt_in = { 0 };
> +	int ret = 0;
> +
> +	pkt_out.fields[SC1810C_STATE_F1_IDX] = SC1810C_SET_STATE_F1;
> +	pkt_out.fields[SC1810C_STATE_F2_IDX] = SC1810C_SET_STATE_F2;
> +	ret = snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0),
> +			      SC1810C_SET_STATE_REQ,
> +			      SC1810C_SET_STATE_REQTYPE,
> +			      (*seqnum), 0, &pkt_out, sizeof(pkt_out));
> +	if (ret < 0) {
> +		dev_warn(&dev->dev, "could not send state packet (%d)\n", ret);
> +		return ret;
> +	}
> +
> +	ret = snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0),
> +			      SC1810C_GET_STATE_REQ,
> +			      SC1810C_GET_STATE_REQTYPE,
> +			      (*seqnum), 0, &pkt_in, sizeof(pkt_in));
> +	if (ret < 0) {
> +		dev_warn(&dev->dev, "could not get state field %u (%d)\n",
> +			 field_idx, ret);
> +		return ret;
> +	}
> +
> +	(*field) = pkt_in.fields[field_idx];
> +	(*seqnum)++;
> +	return 0;
> +}
> +
> +/*
> + * This is what I got when bypassing the mixer with
> + * all channels split. I'm not 100% sure of what's going
> + * on, I could probably clean this up based on my observations
> + * but I prefer to keep the same behavior as the windows driver.
> + */
> +static int snd_s1810c_init_mixer_maps(struct snd_usb_audio *chip)
> +{
> +	u32 a, b, c, e, n, off;
> +	struct usb_device *dev = chip->dev;
> +
> +	/* Set initial volume levels ? */
> +	a = 0x64;
> +	e = 0xbc;
> +	for (n = 0; n < 2; n++) {
> +		off = n * 18;
> +		for (b = off, c = 0; b < 18 + off; b++) {
> +			/* This channel to all outputs ? */
> +			for (c = 0; c <= 8; c++) {
> +				snd_s1810c_send_ctl_packet(dev, a, b, c, 0, e);
> +				snd_s1810c_send_ctl_packet(dev, a, b, c, 1, e);
> +			}
> +			/* This channel to main output (again) */
> +			snd_s1810c_send_ctl_packet(dev, a, b, 0, 0, e);
> +			snd_s1810c_send_ctl_packet(dev, a, b, 0, 1, e);
> +		}
> +		/*
> +		 * I noticed on UC that DAW channels have different
> +		 * initial volumes, so this makes sense.
> +		 */
> +		e = 0xb53bf0;
> +	}
> +
> +	/* Connect analog outputs ? */
> +	a = 0x65;
> +	e = 0x01000000;
> +	for (b = 1; b < 3; b++) {
> +		snd_s1810c_send_ctl_packet(dev, a, b, 0, 0, e);
> +		snd_s1810c_send_ctl_packet(dev, a, b, 0, 1, e);
> +	}
> +	snd_s1810c_send_ctl_packet(dev, a, 0, 0, 0, e);
> +	snd_s1810c_send_ctl_packet(dev, a, 0, 0, 1, e);
> +
> +	/* Set initial volume levels for S/PDIF mappings ? */
> +	a = 0x64;
> +	e = 0xbc;
> +	c = 3;
> +	for (n = 0; n < 2; n++) {
> +		off = n * 18;
> +		for (b = off; b < 18 + off; b++) {
> +			snd_s1810c_send_ctl_packet(dev, a, b, c, 0, e);
> +			snd_s1810c_send_ctl_packet(dev, a, b, c, 1, e);
> +		}
> +		e = 0xb53bf0;
> +	}
> +
> +	/* Connect S/PDIF output ? */
> +	a = 0x65;
> +	e = 0x01000000;
> +	snd_s1810c_send_ctl_packet(dev, a, 3, 0, 0, e);
> +	snd_s1810c_send_ctl_packet(dev, a, 3, 0, 1, e);
> +
> +	/* Connect all outputs (again) ? */
> +	a = 0x65;
> +	e = 0x01000000;
> +	for (b = 0; b < 4; b++) {
> +		snd_s1810c_send_ctl_packet(dev, a, b, 0, 0, e);
> +		snd_s1810c_send_ctl_packet(dev, a, b, 0, 1, e);
> +	}
> +
> +	/* Basic routing to get sound out of the device */
> +	a = 0x64;
> +	e = 0x01000000;
> +	for (c = 0; c < 4; c++) {
> +		for (b = 0; b < 36; b++) {
> +			if ((c == 0 && b == 18) ||	/* DAW1/2 -> Main */
> +			    (c == 1 && b == 20) ||	/* DAW3/4 -> Line3/4 */
> +			    (c == 2 && b == 22) ||	/* DAW4/5 -> Line5/6 */
> +			    (c == 3 && b == 24)) {	/* DAW5/6 -> S/PDIF */
> +				/* Left */
> +				snd_s1810c_send_ctl_packet(dev, a, b, c, 0, e);
> +				snd_s1810c_send_ctl_packet(dev, a, b, c, 1, 0);
> +				b++;
> +				/* Right */
> +				snd_s1810c_send_ctl_packet(dev, a, b, c, 0, 0);
> +				snd_s1810c_send_ctl_packet(dev, a, b, c, 1, e);
> +			} else {
> +				/* Leave the rest disconnected */
> +				snd_s1810c_send_ctl_packet(dev, a, b, c, 0, 0);
> +				snd_s1810c_send_ctl_packet(dev, a, b, c, 1, 0);
> +			}
> +		}
> +	}
> +
> +	/* Set initial volume levels for S/PDIF (again) ? */
> +	a = 0x64;
> +	e = 0xbc;
> +	c = 3;
> +	for (n = 0; n < 2; n++) {
> +		off = n * 18;
> +		for (b = off; b < 18 + off; b++) {
> +			snd_s1810c_send_ctl_packet(dev, a, b, c, 0, e);
> +			snd_s1810c_send_ctl_packet(dev, a, b, c, 1, e);
> +		}
> +		e = 0xb53bf0;
> +	}
> +
> +	/* Connect S/PDIF outputs (again) ? */
> +	a = 0x65;
> +	e = 0x01000000;
> +	snd_s1810c_send_ctl_packet(dev, a, 3, 0, 0, e);
> +	snd_s1810c_send_ctl_packet(dev, a, 3, 0, 1, e);
> +
> +	/* Again ? */
> +	snd_s1810c_send_ctl_packet(dev, a, 3, 0, 0, e);
> +	snd_s1810c_send_ctl_packet(dev, a, 3, 0, 1, e);
> +
> +	return 0;
> +}
> +
> +/*
> + * Sync state with the device and retrieve the requested field,
> + * whose index is specified in (kctl->private_value & 0xFF),
> + * from the received fields array.
> + */
> +static int
> +snd_s1810c_get_switch_state(struct usb_mixer_interface *mixer,
> +			    struct snd_kcontrol *kctl, u32 *state)
> +{
> +	struct snd_usb_audio *chip = mixer->chip;
> +	struct s1810_mixer_state *private = mixer->private_data;
> +	u32 field = 0;
> +	u32 ctl_idx = (u32) (kctl->private_value & 0xFF);
> +	int ret = 0;
> +
> +	mutex_lock(&private->usb_mutex);
> +	ret = snd_sc1810c_get_status_field(chip->dev, &field,
> +					   ctl_idx, &private->seqnum);
> +	if (ret < 0)
> +		goto unlock;
> +
> +	*state = field;
> + unlock:
> +	mutex_unlock(&private->usb_mutex);
> +	return ret ? ret : 0;
> +}
> +
> +/*
> + * Send a control packet to the device for the control id
> + * specified in (kctl->private_value >> 8) with value
> + * specified in (kctl->private_value >> 16).
> + */
> +static int
> +snd_s1810c_set_switch_state(struct usb_mixer_interface *mixer,
> +			    struct snd_kcontrol *kctl)
> +{
> +	struct snd_usb_audio *chip = mixer->chip;
> +	struct s1810_mixer_state *private = mixer->private_data;
> +	u32 pval = (u32) kctl->private_value;
> +	u32 ctl_id = (pval >> 8) & 0xFF;
> +	u32 ctl_val = (pval >> 16) & 0x1;
> +	int ret = 0;
> +
> +	mutex_lock(&private->usb_mutex);
> +	ret = snd_s1810c_send_ctl_packet(chip->dev, 0, 0, 0, ctl_id, ctl_val);
> +	mutex_unlock(&private->usb_mutex);
> +	return ret;
> +}
> +
> +/* Generic get/set/init functions for switch controls */
> +
> +static int
> +snd_s1810c_switch_get(struct snd_kcontrol *kctl,
> +		      struct snd_ctl_elem_value *ctl_elem)
> +{
> +	struct usb_mixer_elem_list *list = snd_kcontrol_chip(kctl);
> +	struct usb_mixer_interface *mixer = list->mixer;
> +	struct s1810_mixer_state *private = mixer->private_data;
> +	u32 pval = (u32) kctl->private_value;
> +	u32 ctl_idx = pval & 0xFF;
> +	u32 state = 0;
> +	int ret = 0;
> +
> +	mutex_lock(&private->data_mutex);
> +	ret = snd_s1810c_get_switch_state(mixer, kctl, &state);
> +	if (ret < 0)
> +		goto unlock;
> +
> +	switch (ctl_idx) {
> +	case SC1810C_STATE_LINE_SW:
> +	case SC1810C_STATE_AB_SW:
> +		ctl_elem->value.enumerated.item[0] = (int)state;
> +		break;
> +	default:
> +		ctl_elem->value.integer.value[0] = (long)state;
> +	}
> +
> + unlock:
> +	mutex_unlock(&private->data_mutex);
> +	return (ret < 0) ? ret : 0;
> +}
> +
> +static int
> +snd_s1810c_switch_set(struct snd_kcontrol *kctl,
> +		      struct snd_ctl_elem_value *ctl_elem)
> +{
> +	struct usb_mixer_elem_list *list = snd_kcontrol_chip(kctl);
> +	struct usb_mixer_interface *mixer = list->mixer;
> +	struct s1810_mixer_state *private = mixer->private_data;
> +	u32 pval = (u32) kctl->private_value;
> +	u32 ctl_idx = pval & 0xFF;
> +	u32 curval = 0;
> +	u32 newval = 0;
> +	int ret = 0;
> +
> +	mutex_lock(&private->data_mutex);
> +	ret = snd_s1810c_get_switch_state(mixer, kctl, &curval);
> +	if (ret < 0)
> +		goto unlock;
> +
> +	switch (ctl_idx) {
> +	case SC1810C_STATE_LINE_SW:
> +	case SC1810C_STATE_AB_SW:
> +		newval = (u32) ctl_elem->value.enumerated.item[0];
> +		break;
> +	default:
> +		newval = (u32) ctl_elem->value.integer.value[0];
> +	}
> +
> +	if (curval == newval)
> +		goto unlock;
> +
> +	kctl->private_value &= ~(0x1 << 16);
> +	kctl->private_value |= (unsigned int)(newval & 0x1) << 16;
> +	ret = snd_s1810c_set_switch_state(mixer, kctl);
> +
> + unlock:
> +	mutex_unlock(&private->data_mutex);
> +	return (ret < 0) ? 0 : 1;
> +}
> +
> +static int
> +snd_s1810c_switch_init(struct usb_mixer_interface *mixer,
> +		       const struct snd_kcontrol_new *new_kctl)
> +{
> +	struct snd_kcontrol *kctl;
> +	struct usb_mixer_elem_info *elem;
> +
> +	elem = kzalloc(sizeof(struct usb_mixer_elem_info), GFP_KERNEL);
> +	if (!elem)
> +		return -ENOMEM;
> +
> +	elem->head.mixer = mixer;
> +	elem->control = 0;
> +	elem->head.id = 0;
> +	elem->channels = 1;
> +
> +	kctl = snd_ctl_new1(new_kctl, elem);
> +	if (!kctl) {
> +		kfree(elem);
> +		return -ENOMEM;
> +	}
> +	kctl->private_free = snd_usb_mixer_elem_free;
> +
> +	return snd_usb_mixer_add_control(&elem->head, kctl);
> +}
> +
> +static int
> +snd_s1810c_line_sw_info(struct snd_kcontrol *kctl,
> +			struct snd_ctl_elem_info *uinfo)
> +{
> +	static const char *const texts[2] = {
> +		"Preamp On (Mic/Inst)",
> +		"Preamp Off (Line in)"
> +	};
> +
> +	return snd_ctl_enum_info(uinfo, 1, ARRAY_SIZE(texts), texts);
> +}
> +
> +static const struct snd_kcontrol_new snd_s1810c_line_sw = {
> +	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
> +	.name = "Line 1/2 Source Type",
> +	.info = snd_s1810c_line_sw_info,
> +	.get = snd_s1810c_switch_get,
> +	.put = snd_s1810c_switch_set,
> +	.private_value = (SC1810C_STATE_LINE_SW | SC1810C_CTL_LINE_SW << 8)
> +};
> +
> +static const struct snd_kcontrol_new snd_s1810c_mute_sw = {
> +	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
> +	.name = "Mute Main Out Switch",
> +	.info = snd_ctl_boolean_mono_info,
> +	.get = snd_s1810c_switch_get,
> +	.put = snd_s1810c_switch_set,
> +	.private_value = (SC1810C_STATE_MUTE_SW | SC1810C_CTL_MUTE_SW << 8)
> +};
> +
> +static const struct snd_kcontrol_new snd_s1810c_48v_sw = {
> +	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
> +	.name = "48V Phantom Power On Mic Inputs Switch",
> +	.info = snd_ctl_boolean_mono_info,
> +	.get = snd_s1810c_switch_get,
> +	.put = snd_s1810c_switch_set,
> +	.private_value = (SC1810C_STATE_48V_SW | SC1810C_CTL_48V_SW << 8)
> +};
> +
> +static int
> +snd_s1810c_ab_sw_info(struct snd_kcontrol *kctl,
> +		      struct snd_ctl_elem_info *uinfo)
> +{
> +	static const char *const texts[2] = {
> +		"1/2",
> +		"3/4"
> +	};
> +
> +	return snd_ctl_enum_info(uinfo, 1, ARRAY_SIZE(texts), texts);
> +}
> +
> +static const struct snd_kcontrol_new snd_s1810c_ab_sw = {
> +	.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
> +	.name = "Headphone 1 Source Route",
> +	.info = snd_s1810c_ab_sw_info,
> +	.get = snd_s1810c_switch_get,
> +	.put = snd_s1810c_switch_set,
> +	.private_value = (SC1810C_STATE_AB_SW | SC1810C_CTL_AB_SW << 8)
> +};
> +
> +static void snd_sc1810_mixer_state_free(struct usb_mixer_interface *mixer)
> +{
> +	struct s1810_mixer_state *private = mixer->private_data;
> +	kfree(private);
> +	mixer->private_data = NULL;
> +}
> +
> +/* Entry point, called from mixer_quirks.c */
> +int snd_sc1810_init_mixer(struct usb_mixer_interface *mixer)
> +{
> +	struct s1810_mixer_state *private = NULL;
> +	struct snd_usb_audio *chip = mixer->chip;
> +	struct usb_device *dev = chip->dev;
> +	int ret = 0;
> +
> +	/* Run this only once */
> +	if (!list_empty(&chip->mixer_list))
> +		return 0;
> +
> +	dev_info(&dev->dev,
> +		 "Presonus Studio 1810c, device_setup: %u\n", chip->setup);
> +	if (chip->setup == 1)
> +		dev_info(&dev->dev, "(8out/18in @ 48KHz)\n");
> +	else if (chip->setup == 2)
> +		dev_info(&dev->dev, "(6out/8in @ 192KHz)\n");
> +	else
> +		dev_info(&dev->dev, "(8out/14in @ 96KHz)\n");
> +
> +	ret = snd_s1810c_init_mixer_maps(chip);
> +	if (ret < 0)
> +		return ret;
> +
> +	private = kzalloc(sizeof(struct s1810_mixer_state), GFP_KERNEL);
> +	if (!private)
> +		return -ENOMEM;
> +
> +	mutex_init(&private->usb_mutex);
> +	mutex_init(&private->data_mutex);
> +
> +	mixer->private_data = private;
> +	mixer->private_free = snd_sc1810_mixer_state_free;
> +
> +	private->seqnum = 1;
> +
> +	ret = snd_s1810c_switch_init(mixer, &snd_s1810c_line_sw);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = snd_s1810c_switch_init(mixer, &snd_s1810c_mute_sw);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = snd_s1810c_switch_init(mixer, &snd_s1810c_48v_sw);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = snd_s1810c_switch_init(mixer, &snd_s1810c_ab_sw);
> +	if (ret < 0)
> +		return ret;
> +	return ret;
> +}
> diff --git a/sound/usb/mixer_s1810c.h b/sound/usb/mixer_s1810c.h
> new file mode 100644
> index 000000000..a79a3743c
> --- /dev/null
> +++ b/sound/usb/mixer_s1810c.h
> @@ -0,0 +1,7 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Presonus Studio 1810c driver for ALSA
> + * Copyright (C) 2019 Nick Kossifidis <mickflemm at gmail.com>
> + */
> +
> +int snd_sc1810_init_mixer(struct usb_mixer_interface *mixer);
> diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c
> index a81c20664..9bbdea882 100644
> --- a/sound/usb/quirks.c
> +++ b/sound/usb/quirks.c
> @@ -1227,6 +1227,38 @@ static int fasttrackpro_skip_setting_quirk(struct snd_usb_audio *chip,
>  	return 0; /* keep this altsetting */
>  }
>  
> +static int s1810c_skip_setting_quirk(struct snd_usb_audio *chip,
> +					   int iface, int altno)
> +{
> +	/*
> +	 * Altno settings:
> +	 *
> +	 * Playback (Interface 1):
> +	 * 1: 6 Analog + 2 S/PDIF
> +	 * 2: 6 Analog + 2 S/PDIF
> +	 * 3: 6 Analog
> +	 *
> +	 * Capture (Interface 2):
> +	 * 1: 8 Analog + 2 S/PDIF + 8 ADAT
> +	 * 2: 8 Analog + 2 S/PDIF + 4 ADAT
> +	 * 3: 8 Analog
> +	 */
> +
> +	/*
> +	 * I'll leave 2 as the default one and
> +	 * use device_setup to switch to the
> +	 * other two.
> +	 */
> +	if ((chip->setup == 0 || chip->setup > 2) && altno != 2)
> +		return 1;
> +	else if (chip->setup == 1 && altno != 1)
> +		return 1;
> +	else if (chip->setup == 2 && altno != 3)
> +		return 1;
> +
> +	return 0;
> +}
> +
>  int snd_usb_apply_interface_quirk(struct snd_usb_audio *chip,
>  				  int iface,
>  				  int altno)
> @@ -1240,6 +1272,10 @@ int snd_usb_apply_interface_quirk(struct snd_usb_audio *chip,
>  	/* fasttrackpro usb: skip altsets incompatible with device_setup */
>  	if (chip->usb_id == USB_ID(0x0763, 0x2012))
>  		return fasttrackpro_skip_setting_quirk(chip, iface, altno);
> +	/* presonus studio 1810c: skip altsets incompatible with device_setup */
> +	if (chip->usb_id == USB_ID(0x0194f, 0x010c))
> +		return s1810c_skip_setting_quirk(chip, iface, altno);
> +
>  
>  	return 0;
>  }
> -- 
> 2.23.0
> 


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