ALSA: usb-audio: Check valid altsetting at parsing rates for UAC2/3

The current driver code assumes blindly that all found sample rates for
the same endpoint from the UAC2 and UAC3 descriptors can be used no
matter which altsetting, but actually this was wrong: some devices
accept only limited sample rates in each altsetting.  For determining
which altsetting supports which rate, we need to verify each sample rate
and check the validity via UAC2_AS_VAL_ALT_SETTINGS.  This control
reports back the available altsettings as a bitmap.

This patch implements the missing piece above, the verification and
reconstructs the sample rate tables based on the result.

An open question is how to deal with the altsettings that ended up
with no valid sample rates after verification.  At least, there is a
device that showed this problem although the sample rates did work in
the later usage (see bug link).  For now, we accept such an altset as
is, assuming that it's a firmware bug.

Reported-by: Dylan Robinson <dylan_robinson@motu.com>
Tested-by: Keith Milner <kamilner@superlative.org>
Tested-by: Dylan Robinson <dylan_robinson@motu.com>
BugLink: https://bugzilla.suse.com/show_bug.cgi?id=1178203
Link: https://lore.kernel.org/r/20201123085347.19667-4-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 93 insertions, 0 deletions

diff --git a/sound/usb/format.c b/sound/usb/format.c
index 3bfead393aa3..3348032daa16 100644
--- a/sound/usb/format.c
+++ b/sound/usb/format.c
@@ -417,6 +417,97 @@ static int line6_parse_audio_format_rates_quirk(struct snd_usb_audio *chip,
 	return -ENODEV;
 }
 
+/* check whether the given altsetting is supported for the already set rate */
+static bool check_valid_altsetting_v2v3(struct snd_usb_audio *chip, int iface,
+					int altsetting)
+{
+	struct usb_device *dev = chip->dev;
+	__le64 raw_data = 0;
+	u64 data;
+	int err;
+
+	/* we assume 64bit is enough for any altsettings */
+	if (snd_BUG_ON(altsetting >= 64 - 8))
+		return false;
+
+	err = snd_usb_ctl_msg(dev, usb_sndctrlpipe(dev, 0), UAC2_CS_CUR,
+			      USB_TYPE_CLASS | USB_RECIP_INTERFACE | USB_DIR_IN,
+			      UAC2_AS_VAL_ALT_SETTINGS << 8,
+			      iface, &raw_data, sizeof(raw_data));
+	if (err < 0)
+		return false;
+
+	data = le64_to_cpu(raw_data);
+	/* first byte contains the bitmap size */
+	if ((data & 0xff) * 8 < altsetting)
+		return false;
+	if (data & (1ULL << (altsetting + 8)))
+		return true;
+
+	return false;
+}
+
+/*
+ * Validate each sample rate with the altsetting
+ * Rebuild the rate table if only partial values are valid
+ */
+static int validate_sample_rate_table_v2v3(struct snd_usb_audio *chip,
+					   struct audioformat *fp,
+					   int clock)
+{
+	struct usb_device *dev = chip->dev;
+	unsigned int *table;
+	unsigned int nr_rates;
+	unsigned int rate_min = 0x7fffffff;
+	unsigned int rate_max = 0;
+	unsigned int rates = 0;
+	int i, err;
+
+	table = kcalloc(fp->nr_rates, sizeof(*table), GFP_KERNEL);
+	if (!table)
+		return -ENOMEM;
+
+	/* clear the interface altsetting at first */
+	usb_set_interface(dev, fp->iface, 0);
+
+	nr_rates = 0;
+	for (i = 0; i < fp->nr_rates; i++) {
+		err = snd_usb_set_sample_rate_v2v3(chip, fp, clock,
+						   fp->rate_table[i]);
+		if (err < 0)
+			continue;
+
+		if (check_valid_altsetting_v2v3(chip, fp->iface, fp->altsetting)) {
+			table[nr_rates++] = fp->rate_table[i];
+			if (rate_min > fp->rate_table[i])
+				rate_min = fp->rate_table[i];
+			if (rate_max < fp->rate_table[i])
+				rate_max = fp->rate_table[i];
+			rates |= snd_pcm_rate_to_rate_bit(fp->rate_table[i]);
+		}
+	}
+
+	if (!nr_rates) {
+		usb_audio_dbg(chip,
+			      "No valid sample rate available for %d:%d, assuming a firmware bug\n",
+			      fp->iface, fp->altsetting);
+		nr_rates = fp->nr_rates; /* continue as is */
+	}
+
+	if (fp->nr_rates == nr_rates) {
+		kfree(table);
+		return 0;
+	}
+
+	kfree(fp->rate_table);
+	fp->rate_table = table;
+	fp->nr_rates = nr_rates;
+	fp->rate_min = rate_min;
+	fp->rate_max = rate_max;
+	fp->rates = rates;
+	return 0;
+}
+
 /*
  * parse the format descriptor and stores the possible sample rates
  * on the audioformat table (audio class v2 and v3).
@@ -509,6 +600,8 @@ static int parse_audio_format_rates_v2v3(struct snd_usb_audio *chip,
 	 * allocated, so the rates will be stored */
 	parse_uac2_sample_rate_range(chip, fp, nr_triplets, data);
 
+	ret = validate_sample_rate_table_v2v3(chip, fp, clock);
+
 err_free:
 	kfree(data);
 err: