* [PATCH v3 1/3] usb: gadget: f_uac2: avoid truncating calculated bandwidth
2026-11-03 21:14 [PATCH v3 0/3] usb: gadget: f_uac2: allow explicit channel count independent of channel mask Kyle Farrell
@ 2026-11-03 21:14 ` Kyle Farrell
2026-11-03 21:25 ` sashiko-bot
2026-11-03 21:14 ` [PATCH v3 2/3] usb: gadget: u_audio: pass channel counts explicitly Kyle Farrell
2026-11-03 21:14 ` [PATCH v3 3/3] usb: gadget: f_uac2: allow explicit channel count independent of channel mask Kyle Farrell
2 siblings, 1 reply; 7+ messages in thread
From: Kyle Farrell @ 2026-11-03 21:14 UTC (permalink / raw)
To: nkapron, gregkh
Cc: corbet, skhan, rdunlap, linux-usb, linux-doc, flavra,
Kyle Farrell
get_max_bw_for_bint() calculates the required bandwidth using 32-bit
arithmetic and stores the result in a u16. A result above U16_MAX
is truncated before set_ep_max_packet_size_bint() compares it against
the endpoint maximum. The truncated value can appear to fit, bypassing
the clamp and warning and advertising a too-small wMaxPacketSize.
Use u32 for the calculated value, the return type of
get_max_bw_for_bint() and the caller's local variable, and print it
with %u. A packet size above the endpoint maximum remains clamped
before it is stored in the 16-bit wMaxPacketSize field.
Signed-off-by: Kyle Farrell <kaf@nwlink.com>
---
drivers/usb/gadget/function/f_uac2.c | 22 ++++++++++++----------
1 file changed, 12 insertions(+), 10 deletions(-)
diff --git a/drivers/usb/gadget/function/f_uac2.c b/drivers/usb/gadget/function/f_uac2.c
index d8cf710085a0..b519382df0b3 100644
--- a/drivers/usb/gadget/function/f_uac2.c
+++ b/drivers/usb/gadget/function/f_uac2.c
@@ -668,18 +668,19 @@ static int get_max_srate(const int *srates)
return max_srate;
}
-static int get_max_bw_for_bint(const struct f_uac2_opts *uac2_opts,
+static u32 get_max_bw_for_bint(const struct f_uac2_opts *uac2_opts,
u8 bint, unsigned int factor, bool is_playback)
{
- int chmask, srate, ssize;
- u16 max_size_bw;
+ unsigned int channels;
+ int srate, ssize;
+ u32 max_size_bw;
if (is_playback) {
- chmask = uac2_opts->p_chmask;
+ channels = num_channels(uac2_opts->p_chmask);
srate = get_max_srate(uac2_opts->p_srates);
ssize = uac2_opts->p_ssize;
} else {
- chmask = uac2_opts->c_chmask;
+ channels = num_channels(uac2_opts->c_chmask);
srate = get_max_srate(uac2_opts->c_srates);
ssize = uac2_opts->c_ssize;
}
@@ -689,11 +690,11 @@ static int get_max_bw_for_bint(const struct f_uac2_opts *uac2_opts,
// Win10 requires max packet size + 1 frame
srate = srate * (1000 + uac2_opts->fb_max) / 1000;
// updated srate is always bigger, therefore DIV_ROUND_UP always yields +1
- max_size_bw = num_channels(chmask) * ssize *
+ max_size_bw = channels * ssize *
(DIV_ROUND_UP(srate, factor / (1 << (bint - 1))));
} else {
// adding 1 frame provision for Win10
- max_size_bw = num_channels(chmask) * ssize *
+ max_size_bw = channels * ssize *
(DIV_ROUND_UP(srate, factor / (1 << (bint - 1))) + 1);
}
return max_size_bw;
@@ -703,7 +704,8 @@ static int set_ep_max_packet_size_bint(struct device *dev, const struct f_uac2_o
struct usb_endpoint_descriptor *ep_desc,
enum usb_device_speed speed, bool is_playback)
{
- u16 max_size_bw, max_size_ep;
+ u32 max_size_bw;
+ u16 max_size_ep;
u8 bint, opts_bint;
char *dir;
@@ -749,11 +751,11 @@ static int set_ep_max_packet_size_bint(struct device *dev, const struct f_uac2_o
if (max_size_bw <= max_size_ep)
dev_dbg(dev,
- "%s %s: Would use wMaxPacketSize %d and bInterval %d\n",
+ "%s %s: Would use wMaxPacketSize %u and bInterval %d\n",
speed_names[speed], dir, max_size_bw, bint);
else {
dev_warn(dev,
- "%s %s: Req. wMaxPacketSize %d at bInterval %d > max ISOC %d, may drop data!\n",
+ "%s %s: Req. wMaxPacketSize %u at bInterval %d > max ISOC %d, may drop data!\n",
speed_names[speed], dir, max_size_bw, bint, max_size_ep);
max_size_bw = max_size_ep;
}
--
2.34.1
^ permalink raw reply related [flat|nested] 7+ messages in thread* [PATCH v3 2/3] usb: gadget: u_audio: pass channel counts explicitly
2026-11-03 21:14 [PATCH v3 0/3] usb: gadget: f_uac2: allow explicit channel count independent of channel mask Kyle Farrell
2026-11-03 21:14 ` [PATCH v3 1/3] usb: gadget: f_uac2: avoid truncating calculated bandwidth Kyle Farrell
@ 2026-11-03 21:14 ` Kyle Farrell
2026-11-03 21:24 ` sashiko-bot
2026-11-03 21:14 ` [PATCH v3 3/3] usb: gadget: f_uac2: allow explicit channel count independent of channel mask Kyle Farrell
2 siblings, 1 reply; 7+ messages in thread
From: Kyle Farrell @ 2026-11-03 21:14 UTC (permalink / raw)
To: nkapron, gregkh
Cc: corbet, skhan, rdunlap, linux-usb, linux-doc, flavra,
Kyle Farrell
u_audio currently derives the channel count from the channel mask in
struct uac_params in several places. Instead, pass the resolved count
explicitly, so the shared audio implementation does not depend on how
an individual USB audio function represents its channel configuration.
Initialize the channel counts from the existing masks in f_uac1 and
f_uac2. Remove the now-unused channel mask fields from uac_params.
Preserve existing behavior.
Signed-off-by: Kyle Farrell <kaf@nwlink.com>
---
drivers/usb/gadget/function/f_uac1.c | 4 ++--
drivers/usb/gadget/function/f_uac2.c | 4 ++--
drivers/usb/gadget/function/u_audio.c | 32 ++++++++++++---------------
drivers/usb/gadget/function/u_audio.h | 4 ++--
4 files changed, 20 insertions(+), 24 deletions(-)
diff --git a/drivers/usb/gadget/function/f_uac1.c b/drivers/usb/gadget/function/f_uac1.c
index 7a81cd176abd..7d912696cec2 100644
--- a/drivers/usb/gadget/function/f_uac1.c
+++ b/drivers/usb/gadget/function/f_uac1.c
@@ -1447,7 +1447,7 @@ static int f_audio_bind(struct usb_configuration *c, struct usb_function *f)
audio->out_ep_maxpsize = le16_to_cpu(as_out_ep_desc.wMaxPacketSize);
audio->in_ep_maxpsize = le16_to_cpu(as_in_ep_desc.wMaxPacketSize);
- audio->params.c_chmask = audio_opts->c_chmask;
+ audio->params.c_channels = num_channels(audio_opts->c_chmask);
memcpy(audio->params.c_srates, audio_opts->c_srates,
sizeof(audio->params.c_srates));
audio->params.c_ssize = audio_opts->c_ssize;
@@ -1460,7 +1460,7 @@ static int f_audio_bind(struct usb_configuration *c, struct usb_function *f)
audio->params.p_fu.volume_max = audio_opts->p_volume_max;
audio->params.p_fu.volume_res = audio_opts->p_volume_res;
}
- audio->params.p_chmask = audio_opts->p_chmask;
+ audio->params.p_channels = num_channels(audio_opts->p_chmask);
memcpy(audio->params.p_srates, audio_opts->p_srates,
sizeof(audio->params.p_srates));
audio->params.p_ssize = audio_opts->p_ssize;
diff --git a/drivers/usb/gadget/function/f_uac2.c b/drivers/usb/gadget/function/f_uac2.c
index b519382df0b3..19578fbc6af5 100644
--- a/drivers/usb/gadget/function/f_uac2.c
+++ b/drivers/usb/gadget/function/f_uac2.c
@@ -1309,7 +1309,7 @@ afunc_bind(struct usb_configuration *cfg, struct usb_function *fn)
agdev->gadget = gadget;
- agdev->params.p_chmask = uac2_opts->p_chmask;
+ agdev->params.p_channels = num_channels(uac2_opts->p_chmask);
memcpy(agdev->params.p_srates, uac2_opts->p_srates,
sizeof(agdev->params.p_srates));
agdev->params.p_ssize = uac2_opts->p_ssize;
@@ -1321,7 +1321,7 @@ afunc_bind(struct usb_configuration *cfg, struct usb_function *fn)
agdev->params.p_fu.volume_max = uac2_opts->p_volume_max;
agdev->params.p_fu.volume_res = uac2_opts->p_volume_res;
}
- agdev->params.c_chmask = uac2_opts->c_chmask;
+ agdev->params.c_channels = num_channels(uac2_opts->c_chmask);
memcpy(agdev->params.c_srates, uac2_opts->c_srates,
sizeof(agdev->params.c_srates));
agdev->params.c_ssize = uac2_opts->c_ssize;
diff --git a/drivers/usb/gadget/function/u_audio.c b/drivers/usb/gadget/function/u_audio.c
index f0ee83abcebc..de0622ee72ab 100644
--- a/drivers/usb/gadget/function/u_audio.c
+++ b/drivers/usb/gadget/function/u_audio.c
@@ -390,25 +390,22 @@ static int uac_pcm_open(struct snd_pcm_substream *substream)
struct uac_params *params;
struct uac_rtd_params *prm;
int p_ssize, c_ssize;
- int p_chmask, c_chmask;
audio_dev = uac->audio_dev;
params = &audio_dev->params;
p_ssize = params->p_ssize;
c_ssize = params->c_ssize;
- p_chmask = params->p_chmask;
- c_chmask = params->c_chmask;
uac->p_residue_mil = 0;
runtime->hw = uac_pcm_hardware;
if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
runtime->hw.formats = uac_ssize_to_fmt(p_ssize);
- runtime->hw.channels_min = num_channels(p_chmask);
+ runtime->hw.channels_min = params->p_channels;
prm = &uac->p_prm;
} else {
runtime->hw.formats = uac_ssize_to_fmt(c_ssize);
- runtime->hw.channels_min = num_channels(c_chmask);
+ runtime->hw.channels_min = params->c_channels;
prm = &uac->c_prm;
}
@@ -736,8 +733,7 @@ int u_audio_start_playback(struct g_audio *audio_dev)
factor = 8000;
/* pre-compute some values for iso_complete() */
- uac->p_framesize = params->p_ssize *
- num_channels(params->p_chmask);
+ uac->p_framesize = params->p_ssize * params->p_channels;
uac->p_interval = factor / (1 << (ep_desc->bInterval - 1));
p_pktsize = min_t(unsigned int,
uac->p_framesize *
@@ -1205,7 +1201,7 @@ int g_audio_setup(struct g_audio *g_audio, const char *pcm_name,
struct snd_pcm *pcm;
struct snd_kcontrol *kctl;
struct uac_params *params;
- int p_chmask, c_chmask;
+ unsigned int p_channels, c_channels;
int i, err;
if (!g_audio)
@@ -1218,10 +1214,10 @@ int g_audio_setup(struct g_audio *g_audio, const char *pcm_name,
uac->audio_dev = g_audio;
params = &g_audio->params;
- p_chmask = params->p_chmask;
- c_chmask = params->c_chmask;
+ p_channels = params->p_channels;
+ c_channels = params->c_channels;
- if (c_chmask) {
+ if (c_channels) {
struct uac_rtd_params *prm = &uac->c_prm;
spin_lock_init(&prm->lock);
@@ -1245,7 +1241,7 @@ int g_audio_setup(struct g_audio *g_audio, const char *pcm_name,
}
}
- if (p_chmask) {
+ if (p_channels) {
struct uac_rtd_params *prm = &uac->p_prm;
spin_lock_init(&prm->lock);
@@ -1284,7 +1280,7 @@ int g_audio_setup(struct g_audio *g_audio, const char *pcm_name,
* Create a substream only for non-zero channel streams
*/
err = snd_pcm_new(uac->card, pcm_name, 0,
- p_chmask ? 1 : 0, c_chmask ? 1 : 0, &pcm);
+ p_channels ? 1 : 0, c_channels ? 1 : 0, &pcm);
if (err < 0)
goto snd_fail;
@@ -1299,12 +1295,12 @@ int g_audio_setup(struct g_audio *g_audio, const char *pcm_name,
* Create mixer and controls
* Create only if it's required on USB side
*/
- if ((c_chmask && g_audio->in_ep_fback)
- || (p_chmask && params->p_fu.id)
- || (c_chmask && params->c_fu.id))
+ if ((c_channels && g_audio->in_ep_fback)
+ || (p_channels && params->p_fu.id)
+ || (c_channels && params->c_fu.id))
strscpy(card->mixername, card_name);
- if (c_chmask && g_audio->in_ep_fback) {
+ if (c_channels && g_audio->in_ep_fback) {
kctl = snd_ctl_new1(&u_audio_controls[UAC_FBACK_CTRL],
&uac->c_prm);
if (!kctl) {
@@ -1320,7 +1316,7 @@ int g_audio_setup(struct g_audio *g_audio, const char *pcm_name,
goto snd_fail;
}
- if (p_chmask) {
+ if (p_channels) {
kctl = snd_ctl_new1(&u_audio_controls[UAC_P_PITCH_CTRL],
&uac->p_prm);
if (!kctl) {
diff --git a/drivers/usb/gadget/function/u_audio.h b/drivers/usb/gadget/function/u_audio.h
index 9512b8fccfaa..2e39b49ddacb 100644
--- a/drivers/usb/gadget/function/u_audio.h
+++ b/drivers/usb/gadget/function/u_audio.h
@@ -40,13 +40,13 @@ struct uac_fu_params {
struct uac_params {
/* playback */
- int p_chmask; /* channel mask */
+ unsigned int p_channels; /* resolved number of channels */
int p_srates[UAC_MAX_RATES]; /* available rates in Hz (0 terminated list) */
int p_ssize; /* sample size */
struct uac_fu_params p_fu; /* Feature Unit parameters */
/* capture */
- int c_chmask; /* channel mask */
+ unsigned int c_channels; /* resolved number of channels */
int c_srates[UAC_MAX_RATES]; /* available rates in Hz (0 terminated list) */
int c_ssize; /* sample size */
struct uac_fu_params c_fu; /* Feature Unit parameters */
--
2.34.1
^ permalink raw reply related [flat|nested] 7+ messages in thread* [PATCH v3 3/3] usb: gadget: f_uac2: allow explicit channel count independent of channel mask
2026-11-03 21:14 [PATCH v3 0/3] usb: gadget: f_uac2: allow explicit channel count independent of channel mask Kyle Farrell
2026-11-03 21:14 ` [PATCH v3 1/3] usb: gadget: f_uac2: avoid truncating calculated bandwidth Kyle Farrell
2026-11-03 21:14 ` [PATCH v3 2/3] usb: gadget: u_audio: pass channel counts explicitly Kyle Farrell
@ 2026-11-03 21:14 ` Kyle Farrell
2026-11-03 21:24 ` sashiko-bot
2 siblings, 1 reply; 7+ messages in thread
From: Kyle Farrell @ 2026-11-03 21:14 UTC (permalink / raw)
To: nkapron, gregkh
Cc: corbet, skhan, rdunlap, linux-usb, linux-doc, flavra,
Kyle Farrell
The UAC2 gadget driver currently derives bNrChannels from the number
of set bits in bmChannelConfig. Since the bmChannelConfig
channel-location bitmap provides only 27 predefined channel locations,
this limits playback and capture streams to 27 channels. UAC2 allows
bNrChannels to specify up to 255 channels, including channels without
predefined locations in bmChannelConfig.
Add ConfigFS p_channels and c_channels attributes to configure the
playback and capture channel counts explicitly. Preserve the existing
p_chmask and c_chmask interface and semantics. The default value of
zero for p_channels and c_channels continues to derive the channel count
from the corresponding p_chmask and c_chmask.
When an explicit channel count and a nonzero channel mask are both
specified, require the number of set bits in the mask to match the
channel count. Partial channel-location assignments permitted by UAC2
are therefore not supported. Additionally, reject Feature Unit
configurations whose descriptor length would exceed the one-byte
bLength field.
Signed-off-by: Kyle Farrell <kaf@nwlink.com>
---
.../ABI/testing/configfs-usb-gadget-uac2 | 18 ++++-
Documentation/usb/gadget-testing.rst | 18 ++++-
drivers/usb/gadget/function/f_uac2.c | 66 ++++++++++++++-----
drivers/usb/gadget/function/u_uac2.h | 4 ++
4 files changed, 85 insertions(+), 21 deletions(-)
diff --git a/Documentation/ABI/testing/configfs-usb-gadget-uac2 b/Documentation/ABI/testing/configfs-usb-gadget-uac2
index 133e995c3e92..8e264843e492 100644
--- a/Documentation/ABI/testing/configfs-usb-gadget-uac2
+++ b/Documentation/ABI/testing/configfs-usb-gadget-uac2
@@ -5,7 +5,14 @@ Description:
The attributes:
===================== =======================================
- c_chmask capture channel mask
+ c_chmask capture channel-location mask. The number of
+ capture channels is derived from the number of
+ set bits unless c_channels is specified.
+ c_channels explicit capture channel count. A value of 0
+ derives the channel count from c_chmask. When
+ nonzero, c_chmask specifies channel locations
+ and may be 0. If both c_channels and c_chmask
+ are nonzero, the values must agree.
c_srate list of capture sampling rates (comma-separated)
c_ssize capture sample size (bytes)
c_hs_bint capture bInterval for HS/SS (1-4: fixed, 0: auto)
@@ -20,7 +27,14 @@ Description:
c_volume_res capture volume control resolution
(in 1/256 dB)
fb_max maximum extra bandwidth in async mode
- p_chmask playback channel mask
+ p_chmask playback channel-location mask. The number of
+ playback channels is derived from the number of
+ set bits unless p_channels is specified.
+ p_channels explicit playback channel count. A value of 0
+ derives the channel count from p_chmask. When
+ nonzero, p_chmask specifies channel locations
+ and may be 0. If both p_channels and p_chmask
+ are nonzero, the values must agree.
p_srate list of playback sampling rates (comma-separated)
p_ssize playback sample size (bytes)
p_hs_bint playback bInterval for HS/SS (1-4: fixed, 0: auto)
diff --git a/Documentation/usb/gadget-testing.rst b/Documentation/usb/gadget-testing.rst
index 4921e5307d49..c050218291d1 100644
--- a/Documentation/usb/gadget-testing.rst
+++ b/Documentation/usb/gadget-testing.rst
@@ -741,7 +741,14 @@ The function name to use when creating the function directory is "uac2".
The uac2 function provides these attributes in its function directory:
================ ====================================================
- c_chmask capture channel mask
+ c_chmask capture channel-location mask. The number of
+ capture channels is derived from the number of
+ set bits unless c_channels is specified.
+ c_channels explicit capture channel count. A value of 0
+ derives the channel count from c_chmask. When
+ nonzero, c_chmask specifies channel locations
+ and may be 0. If both c_channels and c_chmask
+ are nonzero, the values must agree.
c_srate list of capture sampling rates (comma-separated)
c_ssize capture sample size (bytes)
c_sync capture synchronization type (async/adaptive)
@@ -752,7 +759,14 @@ The uac2 function provides these attributes in its function directory:
c_volume_res capture volume control resolution (in 1/256 dB)
c_hs_bint capture bInterval for HS/SS (1-4: fixed, 0: auto)
fb_max maximum extra bandwidth in async mode
- p_chmask playback channel mask
+ p_chmask playback channel-location mask. The number of
+ playback channels is derived from the number of
+ set bits unless p_channels is specified.
+ p_channels explicit playback channel count. A value of 0
+ derives the channel count from p_chmask. When
+ nonzero, p_chmask specifies channel locations
+ and may be 0. If both p_channels and p_chmask
+ are nonzero, the values must agree.
p_srate list of playback sampling rates (comma-separated)
p_ssize playback sample size (bytes)
p_mute_present playback mute control enable
diff --git a/drivers/usb/gadget/function/f_uac2.c b/drivers/usb/gadget/function/f_uac2.c
index 19578fbc6af5..5973484a4233 100644
--- a/drivers/usb/gadget/function/f_uac2.c
+++ b/drivers/usb/gadget/function/f_uac2.c
@@ -50,8 +50,17 @@
#define UNFLW_CTRL 8
#define OVFLW_CTRL 10
-#define EPIN_EN(_opts) ((_opts)->p_chmask != 0)
-#define EPOUT_EN(_opts) ((_opts)->c_chmask != 0)
+static unsigned int uac2_num_channels(bool is_playback,
+ const struct f_uac2_opts *opts)
+{
+ u8 channels = is_playback ? opts->p_channels : opts->c_channels;
+ u32 chmask = is_playback ? opts->p_chmask : opts->c_chmask;
+
+ return channels ? channels : num_channels(chmask);
+}
+
+#define EPIN_EN(_opts) (uac2_num_channels(true, (_opts)) != 0)
+#define EPOUT_EN(_opts) (uac2_num_channels(false, (_opts)) != 0)
#define FUIN_EN(_opts) (EPIN_EN(_opts) \
&& ((_opts)->p_mute_present \
|| (_opts)->p_volume_present))
@@ -676,11 +685,11 @@ static u32 get_max_bw_for_bint(const struct f_uac2_opts *uac2_opts,
u32 max_size_bw;
if (is_playback) {
- channels = num_channels(uac2_opts->p_chmask);
+ channels = uac2_num_channels(true, uac2_opts);
srate = get_max_srate(uac2_opts->p_srates);
ssize = uac2_opts->p_ssize;
} else {
- channels = num_channels(uac2_opts->c_chmask);
+ channels = uac2_num_channels(false, uac2_opts);
srate = get_max_srate(uac2_opts->c_srates);
ssize = uac2_opts->c_ssize;
}
@@ -766,10 +775,9 @@ static int set_ep_max_packet_size_bint(struct device *dev, const struct f_uac2_o
return 0;
}
-static struct uac2_feature_unit_descriptor *build_fu_desc(int chmask)
+static struct uac2_feature_unit_descriptor *build_fu_desc(unsigned int channels)
{
struct uac2_feature_unit_descriptor *fu_desc;
- int channels = num_channels(chmask);
int fu_desc_size = UAC2_DT_FEATURE_UNIT_SIZE(channels);
fu_desc = kzalloc(fu_desc_size, GFP_KERNEL);
@@ -978,13 +986,27 @@ static int afunc_validate_opts(struct g_audio *agdev, struct device *dev)
{
struct f_uac2_opts *opts = g_audio_to_uac2_opts(agdev);
const char *msg = NULL;
+ unsigned int p_channels = uac2_num_channels(true, opts);
+ unsigned int c_channels = uac2_num_channels(false, opts);
- if (!opts->p_chmask && !opts->c_chmask)
- msg = "no playback and capture channels";
- else if (opts->p_chmask & ~UAC2_CHANNEL_MASK)
+ if (opts->p_chmask & ~UAC2_CHANNEL_MASK)
msg = "unsupported playback channels mask";
else if (opts->c_chmask & ~UAC2_CHANNEL_MASK)
msg = "unsupported capture channels mask";
+ else if (!p_channels && !c_channels)
+ msg = "no playback and capture channels";
+ else if (opts->p_channels && opts->p_chmask &&
+ opts->p_channels != num_channels(opts->p_chmask))
+ msg = "playback channel count does not match channel mask";
+ else if (opts->c_channels && opts->c_chmask &&
+ opts->c_channels != num_channels(opts->c_chmask))
+ msg = "capture channel count does not match channel mask";
+ else if (FUIN_EN(opts) &&
+ UAC2_DT_FEATURE_UNIT_SIZE(p_channels) > U8_MAX)
+ msg = "too many playback channels for feature unit descriptor";
+ else if (FUOUT_EN(opts) &&
+ UAC2_DT_FEATURE_UNIT_SIZE(c_channels) > U8_MAX)
+ msg = "too many capture channels for feature unit descriptor";
else if ((opts->p_ssize < 1) || (opts->p_ssize > 4))
msg = "incorrect playback sample size";
else if ((opts->c_ssize < 1) || (opts->c_ssize > 4))
@@ -1061,12 +1083,16 @@ afunc_bind(struct usb_configuration *cfg, struct usb_function *fn)
return PTR_ERR(us);
if (FUOUT_EN(uac2_opts)) {
- out_feature_unit_desc = build_fu_desc(uac2_opts->c_chmask);
+ unsigned int c_channels = uac2_num_channels(false, uac2_opts);
+
+ out_feature_unit_desc = build_fu_desc(c_channels);
if (!out_feature_unit_desc)
return -ENOMEM;
}
if (FUIN_EN(uac2_opts)) {
- in_feature_unit_desc = build_fu_desc(uac2_opts->p_chmask);
+ unsigned int p_channels = uac2_num_channels(true, uac2_opts);
+
+ in_feature_unit_desc = build_fu_desc(p_channels);
if (!in_feature_unit_desc) {
ret = -ENOMEM;
goto err_free_fu;
@@ -1101,13 +1127,13 @@ afunc_bind(struct usb_configuration *cfg, struct usb_function *fn)
/* Initialize the configurable parameters */
- usb_out_it_desc.bNrChannels = num_channels(uac2_opts->c_chmask);
+ usb_out_it_desc.bNrChannels = uac2_num_channels(false, uac2_opts);
usb_out_it_desc.bmChannelConfig = cpu_to_le32(uac2_opts->c_chmask);
- io_in_it_desc.bNrChannels = num_channels(uac2_opts->p_chmask);
+ io_in_it_desc.bNrChannels = uac2_num_channels(true, uac2_opts);
io_in_it_desc.bmChannelConfig = cpu_to_le32(uac2_opts->p_chmask);
- as_out_hdr_desc.bNrChannels = num_channels(uac2_opts->c_chmask);
+ as_out_hdr_desc.bNrChannels = uac2_num_channels(false, uac2_opts);
as_out_hdr_desc.bmChannelConfig = cpu_to_le32(uac2_opts->c_chmask);
- as_in_hdr_desc.bNrChannels = num_channels(uac2_opts->p_chmask);
+ as_in_hdr_desc.bNrChannels = uac2_num_channels(true, uac2_opts);
as_in_hdr_desc.bmChannelConfig = cpu_to_le32(uac2_opts->p_chmask);
as_out_fmt1_desc.bSubslotSize = uac2_opts->c_ssize;
as_out_fmt1_desc.bBitResolution = uac2_opts->c_ssize * 8;
@@ -1309,7 +1335,7 @@ afunc_bind(struct usb_configuration *cfg, struct usb_function *fn)
agdev->gadget = gadget;
- agdev->params.p_channels = num_channels(uac2_opts->p_chmask);
+ agdev->params.p_channels = uac2_num_channels(true, uac2_opts);
memcpy(agdev->params.p_srates, uac2_opts->p_srates,
sizeof(agdev->params.p_srates));
agdev->params.p_ssize = uac2_opts->p_ssize;
@@ -1321,7 +1347,7 @@ afunc_bind(struct usb_configuration *cfg, struct usb_function *fn)
agdev->params.p_fu.volume_max = uac2_opts->p_volume_max;
agdev->params.p_fu.volume_res = uac2_opts->p_volume_res;
}
- agdev->params.c_channels = num_channels(uac2_opts->c_chmask);
+ agdev->params.c_channels = uac2_num_channels(false, uac2_opts);
memcpy(agdev->params.c_srates, uac2_opts->c_srates,
sizeof(agdev->params.c_srates));
agdev->params.c_ssize = uac2_opts->c_ssize;
@@ -2091,10 +2117,12 @@ end: \
CONFIGFS_ATTR(f_uac2_opts_, name)
UAC2_ATTRIBUTE(u32, p_chmask);
+UAC2_ATTRIBUTE(u8, p_channels);
UAC2_RATE_ATTRIBUTE(p_srate);
UAC2_ATTRIBUTE(u32, p_ssize);
UAC2_ATTRIBUTE(u8, p_hs_bint);
UAC2_ATTRIBUTE(u32, c_chmask);
+UAC2_ATTRIBUTE(u8, c_channels);
UAC2_RATE_ATTRIBUTE(c_srate);
UAC2_ATTRIBUTE_SYNC(c_sync);
UAC2_ATTRIBUTE(u32, c_ssize);
@@ -2134,10 +2162,12 @@ UAC2_ATTRIBUTE(s16, c_terminal_type);
static struct configfs_attribute *f_uac2_attrs[] = {
&f_uac2_opts_attr_p_chmask,
+ &f_uac2_opts_attr_p_channels,
&f_uac2_opts_attr_p_srate,
&f_uac2_opts_attr_p_ssize,
&f_uac2_opts_attr_p_hs_bint,
&f_uac2_opts_attr_c_chmask,
+ &f_uac2_opts_attr_c_channels,
&f_uac2_opts_attr_c_srate,
&f_uac2_opts_attr_c_ssize,
&f_uac2_opts_attr_c_hs_bint,
@@ -2207,10 +2237,12 @@ static struct usb_function_instance *afunc_alloc_inst(void)
&f_uac2_func_type);
opts->p_chmask = UAC2_DEF_PCHMASK;
+ opts->p_channels = UAC2_DEF_PCHANNELS;
opts->p_srates[0] = UAC2_DEF_PSRATE;
opts->p_ssize = UAC2_DEF_PSSIZE;
opts->p_hs_bint = UAC2_DEF_PHSBINT;
opts->c_chmask = UAC2_DEF_CCHMASK;
+ opts->c_channels = UAC2_DEF_CCHANNELS;
opts->c_srates[0] = UAC2_DEF_CSRATE;
opts->c_ssize = UAC2_DEF_CSSIZE;
opts->c_hs_bint = UAC2_DEF_CHSBINT;
diff --git a/drivers/usb/gadget/function/u_uac2.h b/drivers/usb/gadget/function/u_uac2.h
index 0df808289ded..bacd841c9df6 100644
--- a/drivers/usb/gadget/function/u_uac2.h
+++ b/drivers/usb/gadget/function/u_uac2.h
@@ -17,10 +17,12 @@
#include "uac_common.h"
#define UAC2_DEF_PCHMASK 0x3
+#define UAC2_DEF_PCHANNELS 0 /* 0 = derive from p_chmask */
#define UAC2_DEF_PSRATE 48000
#define UAC2_DEF_PSSIZE 2
#define UAC2_DEF_PHSBINT 0
#define UAC2_DEF_CCHMASK 0x3
+#define UAC2_DEF_CCHANNELS 0 /* 0 = derive from c_chmask */
#define UAC2_DEF_CSRATE 64000
#define UAC2_DEF_CSSIZE 2
#define UAC2_DEF_CHSBINT 0
@@ -46,11 +48,13 @@ struct f_uac2_opts {
int p_srates[UAC_MAX_RATES];
int p_ssize;
u8 p_hs_bint;
+ u8 p_channels;
int c_chmask;
int c_srates[UAC_MAX_RATES];
int c_ssize;
int c_sync;
u8 c_hs_bint;
+ u8 c_channels;
bool p_mute_present;
bool p_volume_present;
--
2.34.1
^ permalink raw reply related [flat|nested] 7+ messages in thread* Re: [PATCH v3 3/3] usb: gadget: f_uac2: allow explicit channel count independent of channel mask
2026-11-03 21:14 ` [PATCH v3 3/3] usb: gadget: f_uac2: allow explicit channel count independent of channel mask Kyle Farrell
@ 2026-11-03 21:24 ` sashiko-bot
0 siblings, 0 replies; 7+ messages in thread
From: sashiko-bot @ 2026-11-03 21:24 UTC (permalink / raw)
To: Kyle Farrell; +Cc: linux-usb
> The UAC2 gadget driver currently derives bNrChannels from the number
> of set bits in bmChannelConfig. Since the bmChannelConfig
> channel-location bitmap provides only 27 predefined channel locations,
> this limits playback and capture streams to 27 channels. UAC2 allows
> bNrChannels to specify up to 255 channels, including channels without
> predefined locations in bmChannelConfig.
>
> Add ConfigFS p_channels and c_channels attributes to configure the
> playback and capture channel counts explicitly. Preserve the existing
> p_chmask and c_chmask interface and semantics. The default value of
> zero for p_channels and c_channels continues to derive the channel count
> from the corresponding p_chmask and c_chmask.
>
> When an explicit channel count and a nonzero channel mask are both
> specified, require the number of set bits in the mask to match the
> channel count. Partial channel-location assignments permitted by UAC2
> are therefore not supported. Additionally, reject Feature Unit
> configurations whose descriptor length would exceed the one-byte
> bLength field.
>
> Signed-off-by: Kyle Farrell <kaf@nwlink.com>
Sashiko has reviewed this patch and found no issues.
--
Sashiko AI review · https://sashiko.dev/#/patchset/20261103211434.996135-1-kaf@nwlink.com?part=3
^ permalink raw reply [flat|nested] 7+ messages in thread