kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted

Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit
`objtool` errors such as:

    vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a:
    can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd

The reason is that in such builds, the Clang invocation that compiles
the combined Rust plus helpers bitcode emits LLVM bitcode (again) --
the final code generation happens in the linker's LTO step, which the
`-mllvm` trap options passed to Clang do not reach.

This, in turn, means that unreachable traps are missing, and the
impossible paths do not merely fallthrough to the next symbol, but past
the end of their own section, since LTO builds place each function in
its own section.

Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always
emits machine code directly, with the traps in place.

Assisted-by: LLM
Cc: Gary Guo <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 352 insertions, 0 deletions

diff --git a/sound/soc/codecs/cs4341.c b/sound/soc/codecs/cs4341.c
new file mode 100644
index 000000000..a44e6b3c2
--- /dev/null
+++ b/sound/soc/codecs/cs4341.c
@@ -0,0 +1,352 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ *  Cirrus Logic CS4341A ALSA SoC Codec Driver
+ *  Author: Alexander Shiyan <shc_work@mail.ru>
+ */
+
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+#include <linux/spi/spi.h>
+
+#include <sound/pcm.h>
+#include <sound/pcm_params.h>
+#include <sound/soc.h>
+#include <sound/tlv.h>
+
+#define CS4341_REG_MODE1	0x00
+#define CS4341_REG_MODE2	0x01
+#define CS4341_REG_MIX		0x02
+#define CS4341_REG_VOLA		0x03
+#define CS4341_REG_VOLB		0x04
+
+#define CS4341_MODE2_DIF	(7 << 4)
+#define CS4341_MODE2_DIF_I2S_24	(0 << 4)
+#define CS4341_MODE2_DIF_I2S_16	(1 << 4)
+#define CS4341_MODE2_DIF_LJ_24	(2 << 4)
+#define CS4341_MODE2_DIF_RJ_24	(3 << 4)
+#define CS4341_MODE2_DIF_RJ_16	(5 << 4)
+#define CS4341_VOLX_MUTE	(1 << 7)
+
+struct cs4341_priv {
+	unsigned int		fmt;
+	struct regmap		*regmap;
+	struct regmap_config	regcfg;
+};
+
+static const struct reg_default cs4341_reg_defaults[] = {
+	{ CS4341_REG_MODE1,	0x00 },
+	{ CS4341_REG_MODE2,	0x82 },
+	{ CS4341_REG_MIX,	0x49 },
+	{ CS4341_REG_VOLA,	0x80 },
+	{ CS4341_REG_VOLB,	0x80 },
+};
+
+static int cs4341_set_fmt(struct snd_soc_dai *dai, unsigned int format)
+{
+	struct snd_soc_component *component = dai->component;
+	struct cs4341_priv *cs4341 = snd_soc_component_get_drvdata(component);
+
+	switch (format & SND_SOC_DAIFMT_MASTER_MASK) {
+	case SND_SOC_DAIFMT_CBC_CFC:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	switch (format & SND_SOC_DAIFMT_INV_MASK) {
+	case SND_SOC_DAIFMT_NB_NF:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	switch (format & SND_SOC_DAIFMT_FORMAT_MASK) {
+	case SND_SOC_DAIFMT_I2S:
+	case SND_SOC_DAIFMT_LEFT_J:
+	case SND_SOC_DAIFMT_RIGHT_J:
+		cs4341->fmt = format & SND_SOC_DAIFMT_FORMAT_MASK;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int cs4341_hw_params(struct snd_pcm_substream *substream,
+			    struct snd_pcm_hw_params *params,
+			    struct snd_soc_dai *dai)
+{
+	struct snd_soc_component *component = dai->component;
+	struct cs4341_priv *cs4341 = snd_soc_component_get_drvdata(component);
+	unsigned int mode = 0;
+	int b24 = 0;
+
+	switch (params_format(params)) {
+	case SNDRV_PCM_FORMAT_S24_LE:
+		b24 = 1;
+		break;
+	case SNDRV_PCM_FORMAT_S16_LE:
+		break;
+	default:
+		dev_err(component->dev, "Unsupported PCM format 0x%08x.\n",
+			params_format(params));
+		return -EINVAL;
+	}
+
+	switch (cs4341->fmt) {
+	case SND_SOC_DAIFMT_I2S:
+		mode = b24 ? CS4341_MODE2_DIF_I2S_24 : CS4341_MODE2_DIF_I2S_16;
+		break;
+	case SND_SOC_DAIFMT_LEFT_J:
+		mode = CS4341_MODE2_DIF_LJ_24;
+		break;
+	case SND_SOC_DAIFMT_RIGHT_J:
+		mode = b24 ? CS4341_MODE2_DIF_RJ_24 : CS4341_MODE2_DIF_RJ_16;
+		break;
+	default:
+		dev_err(component->dev, "Unsupported DAI format 0x%08x.\n",
+			cs4341->fmt);
+		return -EINVAL;
+	}
+
+	return snd_soc_component_update_bits(component, CS4341_REG_MODE2,
+					     CS4341_MODE2_DIF, mode);
+}
+
+static int cs4341_mute(struct snd_soc_dai *dai, int mute, int direction)
+{
+	struct snd_soc_component *component = dai->component;
+	int ret;
+
+	ret = snd_soc_component_update_bits(component, CS4341_REG_VOLA,
+					    CS4341_VOLX_MUTE,
+					    mute ? CS4341_VOLX_MUTE : 0);
+	if (ret < 0)
+		return ret;
+
+	return snd_soc_component_update_bits(component, CS4341_REG_VOLB,
+					     CS4341_VOLX_MUTE,
+					     mute ? CS4341_VOLX_MUTE : 0);
+}
+
+static DECLARE_TLV_DB_SCALE(out_tlv, -9000, 100, 0);
+
+static const char * const deemph[] = {
+	"None", "44.1k", "48k", "32k",
+};
+
+static const struct soc_enum deemph_enum =
+	SOC_ENUM_SINGLE(CS4341_REG_MODE2, 2, 4, deemph);
+
+static const char * const srzc[] = {
+	"Immediate", "Zero Cross", "Soft Ramp", "SR on ZC",
+};
+
+static const struct soc_enum srzc_enum =
+	SOC_ENUM_SINGLE(CS4341_REG_MIX, 5, 4, srzc);
+
+
+static const struct snd_soc_dapm_widget cs4341_dapm_widgets[] = {
+	SND_SOC_DAPM_DAC("HiFi DAC", NULL, SND_SOC_NOPM, 0, 0),
+	SND_SOC_DAPM_OUTPUT("OutA"),
+	SND_SOC_DAPM_OUTPUT("OutB"),
+};
+
+static const struct snd_soc_dapm_route cs4341_routes[] = {
+	{ "OutA", NULL, "HiFi DAC" },
+	{ "OutB", NULL, "HiFi DAC" },
+	{ "DAC Playback", NULL, "OutA" },
+	{ "DAC Playback", NULL, "OutB" },
+};
+
+static const struct snd_kcontrol_new cs4341_controls[] = {
+	SOC_DOUBLE_R_TLV("Master Playback Volume",
+			 CS4341_REG_VOLA, CS4341_REG_VOLB, 0, 90, 1, out_tlv),
+	SOC_ENUM("De-Emphasis Control", deemph_enum),
+	SOC_ENUM("Soft Ramp Zero Cross Control", srzc_enum),
+	SOC_SINGLE("Auto-Mute Switch", CS4341_REG_MODE2, 7, 1, 0),
+	SOC_SINGLE("Popguard Transient Switch", CS4341_REG_MODE2, 1, 1, 0),
+};
+
+static const struct snd_soc_dai_ops cs4341_dai_ops = {
+	.set_fmt	= cs4341_set_fmt,
+	.hw_params	= cs4341_hw_params,
+	.mute_stream	= cs4341_mute,
+	.no_capture_mute = 1,
+};
+
+static struct snd_soc_dai_driver cs4341_dai = {
+	.name			= "cs4341a-hifi",
+	.playback		= {
+		.stream_name	= "DAC Playback",
+		.channels_min	= 1,
+		.channels_max	= 2,
+		.rates		= SNDRV_PCM_RATE_8000_96000,
+		.formats	= SNDRV_PCM_FMTBIT_S16_LE |
+				  SNDRV_PCM_FMTBIT_S24_LE,
+	},
+	.ops			= &cs4341_dai_ops,
+	.symmetric_rate		= 1,
+};
+
+static const struct snd_soc_component_driver soc_component_cs4341 = {
+	.controls		= cs4341_controls,
+	.num_controls		= ARRAY_SIZE(cs4341_controls),
+	.dapm_widgets		= cs4341_dapm_widgets,
+	.num_dapm_widgets	= ARRAY_SIZE(cs4341_dapm_widgets),
+	.dapm_routes		= cs4341_routes,
+	.num_dapm_routes	= ARRAY_SIZE(cs4341_routes),
+	.idle_bias_on		= 1,
+	.use_pmdown_time	= 1,
+	.endianness		= 1,
+};
+
+static const struct of_device_id __maybe_unused cs4341_dt_ids[] = {
+	{ .compatible = "cirrus,cs4341a", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, cs4341_dt_ids);
+
+static int cs4341_probe(struct device *dev)
+{
+	struct cs4341_priv *cs4341 = dev_get_drvdata(dev);
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(cs4341_reg_defaults); i++)
+		regmap_write(cs4341->regmap, cs4341_reg_defaults[i].reg,
+			     cs4341_reg_defaults[i].def);
+
+	return devm_snd_soc_register_component(dev, &soc_component_cs4341,
+					       &cs4341_dai, 1);
+}
+
+#if IS_ENABLED(CONFIG_I2C)
+static int cs4341_i2c_probe(struct i2c_client *i2c)
+{
+	struct cs4341_priv *cs4341;
+
+	cs4341 = devm_kzalloc(&i2c->dev, sizeof(*cs4341), GFP_KERNEL);
+	if (!cs4341)
+		return -ENOMEM;
+
+	i2c_set_clientdata(i2c, cs4341);
+
+	cs4341->regcfg.reg_bits		= 8;
+	cs4341->regcfg.val_bits		= 8;
+	cs4341->regcfg.max_register	= CS4341_REG_VOLB;
+	cs4341->regcfg.cache_type	= REGCACHE_FLAT;
+	cs4341->regcfg.reg_defaults	= cs4341_reg_defaults;
+	cs4341->regcfg.num_reg_defaults	= ARRAY_SIZE(cs4341_reg_defaults);
+	cs4341->regmap = devm_regmap_init_i2c(i2c, &cs4341->regcfg);
+	if (IS_ERR(cs4341->regmap))
+		return PTR_ERR(cs4341->regmap);
+
+	return cs4341_probe(&i2c->dev);
+}
+
+static const struct i2c_device_id cs4341_i2c_id[] = {
+	{ .name = "cs4341" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, cs4341_i2c_id);
+
+static struct i2c_driver cs4341_i2c_driver = {
+	.driver = {
+		.name = "cs4341-i2c",
+		.of_match_table = of_match_ptr(cs4341_dt_ids),
+	},
+	.probe = cs4341_i2c_probe,
+	.id_table = cs4341_i2c_id,
+};
+#endif
+
+#if defined(CONFIG_SPI_MASTER)
+static bool cs4341_reg_readable(struct device *dev, unsigned int reg)
+{
+	return false;
+}
+
+static int cs4341_spi_probe(struct spi_device *spi)
+{
+	struct cs4341_priv *cs4341;
+	int ret;
+
+	cs4341 = devm_kzalloc(&spi->dev, sizeof(*cs4341), GFP_KERNEL);
+	if (!cs4341)
+		return -ENOMEM;
+
+	if (!spi->bits_per_word)
+		spi->bits_per_word = 8;
+	if (!spi->max_speed_hz)
+		spi->max_speed_hz = 6000000;
+	ret = spi_setup(spi);
+	if (ret)
+		return ret;
+
+	spi_set_drvdata(spi, cs4341);
+
+	cs4341->regcfg.reg_bits		= 16;
+	cs4341->regcfg.val_bits		= 8;
+	cs4341->regcfg.write_flag_mask	= 0x20;
+	cs4341->regcfg.max_register	= CS4341_REG_VOLB;
+	cs4341->regcfg.cache_type	= REGCACHE_FLAT;
+	cs4341->regcfg.readable_reg	= cs4341_reg_readable;
+	cs4341->regcfg.reg_defaults	= cs4341_reg_defaults;
+	cs4341->regcfg.num_reg_defaults	= ARRAY_SIZE(cs4341_reg_defaults);
+	cs4341->regmap = devm_regmap_init_spi(spi, &cs4341->regcfg);
+	if (IS_ERR(cs4341->regmap))
+		return PTR_ERR(cs4341->regmap);
+
+	return cs4341_probe(&spi->dev);
+}
+
+static const struct spi_device_id cs4341_spi_ids[] = {
+	{ "cs4341a" },
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, cs4341_spi_ids);
+
+static struct spi_driver cs4341_spi_driver = {
+	.driver = {
+		.name = "cs4341-spi",
+		.of_match_table = of_match_ptr(cs4341_dt_ids),
+	},
+	.probe = cs4341_spi_probe,
+	.id_table = cs4341_spi_ids,
+};
+#endif
+
+static int __init cs4341_init(void)
+{
+	int ret = 0;
+
+#if IS_ENABLED(CONFIG_I2C)
+	ret = i2c_add_driver(&cs4341_i2c_driver);
+	if (ret)
+		return ret;
+#endif
+#if defined(CONFIG_SPI_MASTER)
+	ret = spi_register_driver(&cs4341_spi_driver);
+#endif
+
+	return ret;
+}
+module_init(cs4341_init);
+
+static void __exit cs4341_exit(void)
+{
+#if IS_ENABLED(CONFIG_I2C)
+	i2c_del_driver(&cs4341_i2c_driver);
+#endif
+#if defined(CONFIG_SPI_MASTER)
+	spi_unregister_driver(&cs4341_spi_driver);
+#endif
+}
+module_exit(cs4341_exit);
+
+MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>");
+MODULE_DESCRIPTION("Cirrus Logic CS4341 ALSA SoC Codec Driver");
+MODULE_LICENSE("GPL");