From: "Ondřej Jirman" <megi@xff.cz>
To: linux-kernel@vger.kernel.org, Liam Girdwood <lgirdwood@gmail.com>,
Mark Brown <broonie@kernel.org>, Jaroslav Kysela <perex@perex.cz>,
Takashi Iwai <tiwai@suse.com>
Cc: Arnaud Ferraris <arnaud.ferraris@collabora.com>,
Chen-Yu Tsai <wens@csie.org>,
Jernej Skrabec <jernej.skrabec@gmail.com>,
Samuel Holland <samuel@sholland.org>, Ondrej Jirman <megi@xff.cz>,
linux-sound@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-sunxi@lists.linux.dev
Subject: [PATCH v3 4/4] ASoC: sun8i-codec: Implement jack and accessory detection
Date: Sat, 2 Mar 2024 15:00:38 +0100 [thread overview]
Message-ID: <20240302140042.1990256-5-megi@xff.cz> (raw)
In-Reply-To: <20240302140042.1990256-1-megi@xff.cz>
From: Arnaud Ferraris <arnaud.ferraris@collabora.com>
Add support for the jack detection functionality in the A64 variant,
which uses a pair of IRQs; and microphone accessory (button) detection,
which uses an ADC with an IRQ trigger.
IRQs will only be triggered if the JACKDETEN, HMICBIASEN, and MICADCEN
bits are set appropriately in the analog codec component
(sun50i-codec-analog), but there is no direct software dependency
between the two components.
Setup ADC so that it samples with period of 16ms, disable smoothing
and enable MDATA threshold (should be below idle voltage/HMIC_DATA
value). Also enable HMIC_N, which makes sure we get HMIC_N samples
after HMIC_DATA crosses the threshold.
This allows us to perform steady state detection of HMIC_DATA, by
comparing current and previous ADC samples, to detect end of the
transient when the user de-presses the button. Otherwise ADC could
sample anywhere within the transient, and the driver may mis-issue
key-press events for other buttons attached to the resistor ladder.
Signed-off-by: Arnaud Ferraris <arnaud.ferraris@collabora.com>
[Samuel: Decouple from analog codec, fixes]
Co-developed-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Samuel Holland <samuel@sholland.org>
[Ondrej: Almost complete rewrite of the patch, change to use set_jack
API. Better de-bounce, fix mic button handling, better interrupt
processing.]
Co-developed-by: Ondrej Jirman <megi@xff.cz>
Signed-off-by: Ondrej Jirman <megi@xff.cz>
---
sound/soc/sunxi/sun50i-codec-analog.c | 12 +
sound/soc/sunxi/sun8i-codec.c | 305 ++++++++++++++++++++++++++
2 files changed, 317 insertions(+)
diff --git a/sound/soc/sunxi/sun50i-codec-analog.c b/sound/soc/sunxi/sun50i-codec-analog.c
index 2081721a8ff2..2dcdf113b66e 100644
--- a/sound/soc/sunxi/sun50i-codec-analog.c
+++ b/sound/soc/sunxi/sun50i-codec-analog.c
@@ -115,6 +115,11 @@
#define SUN50I_ADDA_HS_MBIAS_CTRL 0x0e
#define SUN50I_ADDA_HS_MBIAS_CTRL_MMICBIASEN 7
+#define SUN50I_ADDA_MDET_CTRL 0x1c
+#define SUN50I_ADDA_MDET_CTRL_SELDETADC_FS 4
+#define SUN50I_ADDA_MDET_CTRL_SELDETADC_DB 2
+#define SUN50I_ADDA_MDET_CTRL_SELDETADC_BF 0
+
#define SUN50I_ADDA_JACK_MIC_CTRL 0x1d
#define SUN50I_ADDA_JACK_MIC_CTRL_JACKDETEN 7
#define SUN50I_ADDA_JACK_MIC_CTRL_INNERRESEN 6
@@ -564,6 +569,13 @@ static int sun50i_codec_analog_probe(struct platform_device *pdev)
BIT(SUN50I_ADDA_JACK_MIC_CTRL_INNERRESEN),
enable << SUN50I_ADDA_JACK_MIC_CTRL_INNERRESEN);
+ /* Select sample interval of the ADC sample to 16ms */
+ regmap_update_bits(regmap, SUN50I_ADDA_MDET_CTRL,
+ 0x7 << SUN50I_ADDA_MDET_CTRL_SELDETADC_FS |
+ 0x3 << SUN50I_ADDA_MDET_CTRL_SELDETADC_BF,
+ 0x3 << SUN50I_ADDA_MDET_CTRL_SELDETADC_FS |
+ 0x3 << SUN50I_ADDA_MDET_CTRL_SELDETADC_BF);
+
return devm_snd_soc_register_component(&pdev->dev,
&sun50i_codec_analog_cmpnt_drv,
NULL, 0);
diff --git a/sound/soc/sunxi/sun8i-codec.c b/sound/soc/sunxi/sun8i-codec.c
index 2a46b96b03cc..43795362fed0 100644
--- a/sound/soc/sunxi/sun8i-codec.c
+++ b/sound/soc/sunxi/sun8i-codec.c
@@ -12,12 +12,16 @@
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/clk.h>
+#include <linux/input.h>
#include <linux/io.h>
+#include <linux/irq.h>
+#include <linux/mutex.h>
#include <linux/of.h>
#include <linux/pm_runtime.h>
#include <linux/regmap.h>
#include <linux/log2.h>
+#include <sound/jack.h>
#include <sound/pcm_params.h>
#include <sound/soc.h>
#include <sound/soc-dapm.h>
@@ -118,6 +122,23 @@
#define SUN8I_ADC_VOL_CTRL 0x104
#define SUN8I_ADC_VOL_CTRL_ADCL_VOL 8
#define SUN8I_ADC_VOL_CTRL_ADCR_VOL 0
+#define SUN8I_HMIC_CTRL1 0x110
+#define SUN8I_HMIC_CTRL1_HMIC_M 12
+#define SUN8I_HMIC_CTRL1_HMIC_N 8
+#define SUN8I_HMIC_CTRL1_MDATA_THRESHOLD_DB 5
+#define SUN8I_HMIC_CTRL1_JACK_OUT_IRQ_EN 4
+#define SUN8I_HMIC_CTRL1_JACK_IN_IRQ_EN 3
+#define SUN8I_HMIC_CTRL1_HMIC_DATA_IRQ_EN 0
+#define SUN8I_HMIC_CTRL2 0x114
+#define SUN8I_HMIC_CTRL2_HMIC_SAMPLE 14
+#define SUN8I_HMIC_CTRL2_HMIC_MDATA_THRESHOLD 8
+#define SUN8I_HMIC_CTRL2_HMIC_SF 6
+#define SUN8I_HMIC_STS 0x118
+#define SUN8I_HMIC_STS_MDATA_DISCARD 13
+#define SUN8I_HMIC_STS_HMIC_DATA 8
+#define SUN8I_HMIC_STS_JACK_OUT_IRQ_ST 4
+#define SUN8I_HMIC_STS_JACK_IN_IRQ_ST 3
+#define SUN8I_HMIC_STS_HMIC_DATA_IRQ_ST 0
#define SUN8I_DAC_DIG_CTRL 0x120
#define SUN8I_DAC_DIG_CTRL_ENDA 15
#define SUN8I_DAC_VOL_CTRL 0x124
@@ -143,6 +164,17 @@
#define SUN8I_AIF_CLK_CTRL_WORD_SIZ_MASK GENMASK(5, 4)
#define SUN8I_AIF_CLK_CTRL_DATA_FMT_MASK GENMASK(3, 2)
#define SUN8I_AIF3_CLK_CTRL_AIF3_CLK_SRC_MASK GENMASK(1, 0)
+#define SUN8I_HMIC_CTRL1_HMIC_M_MASK GENMASK(15, 12)
+#define SUN8I_HMIC_CTRL1_HMIC_N_MASK GENMASK(11, 8)
+#define SUN8I_HMIC_CTRL1_MDATA_THRESHOLD_DB_MASK GENMASK(6, 5)
+#define SUN8I_HMIC_CTRL2_HMIC_SAMPLE_MASK GENMASK(15, 14)
+#define SUN8I_HMIC_CTRL2_HMIC_SF_MASK GENMASK(7, 6)
+#define SUN8I_HMIC_STS_HMIC_DATA_MASK GENMASK(12, 8)
+
+#define SUN8I_CODEC_BUTTONS (SND_JACK_BTN_0|\
+ SND_JACK_BTN_1|\
+ SND_JACK_BTN_2|\
+ SND_JACK_BTN_3)
#define SUN8I_CODEC_PASSTHROUGH_SAMPLE_RATE 48000
@@ -178,16 +210,32 @@ struct sun8i_codec_aif {
struct sun8i_codec_quirks {
bool bus_clock : 1;
+ bool jack_detection : 1;
bool legacy_widgets : 1;
bool lrck_inversion : 1;
};
+enum {
+ SUN8I_JACK_STATUS_DISCONNECTED,
+ SUN8I_JACK_STATUS_WAITING_HBIAS,
+ SUN8I_JACK_STATUS_CONNECTED,
+};
+
struct sun8i_codec {
+ struct snd_soc_component *component;
struct regmap *regmap;
struct clk *clk_bus;
struct clk *clk_module;
const struct sun8i_codec_quirks *quirks;
struct sun8i_codec_aif aifs[SUN8I_CODEC_NAIFS];
+ struct snd_soc_jack *jack;
+ struct delayed_work jack_work;
+ int jack_irq;
+ int jack_status;
+ int jack_last_sample;
+ ktime_t jack_hbias_ready;
+ struct mutex jack_mutex;
+ int last_hmic_irq;
unsigned int sysclk_rate;
int sysclk_refcnt;
};
@@ -1245,6 +1293,8 @@ static int sun8i_codec_component_probe(struct snd_soc_component *component)
struct sun8i_codec *scodec = snd_soc_component_get_drvdata(component);
int ret;
+ scodec->component = component;
+
/* Add widgets for backward compatibility with old device trees. */
if (scodec->quirks->legacy_widgets) {
ret = snd_soc_dapm_new_controls(dapm, sun8i_codec_legacy_widgets,
@@ -1281,6 +1331,251 @@ static int sun8i_codec_component_probe(struct snd_soc_component *component)
return 0;
}
+static void sun8i_codec_set_hmic_bias(struct sun8i_codec *scodec, bool enable)
+{
+ struct snd_soc_dapm_context *dapm = &scodec->component->card->dapm;
+ int irq_mask = BIT(SUN8I_HMIC_CTRL1_HMIC_DATA_IRQ_EN);
+
+ if (enable)
+ snd_soc_dapm_force_enable_pin(dapm, "HBIAS");
+ else
+ snd_soc_dapm_disable_pin(dapm, "HBIAS");
+
+ snd_soc_dapm_sync(dapm);
+
+ regmap_update_bits(scodec->regmap, SUN8I_HMIC_CTRL1,
+ irq_mask, enable ? irq_mask : 0);
+}
+
+static void sun8i_codec_jack_work(struct work_struct *work)
+{
+ struct sun8i_codec *scodec = container_of(work, struct sun8i_codec,
+ jack_work.work);
+ unsigned int mdata;
+ int type_mask = scodec->jack->jack->type;
+ int type;
+
+ guard(mutex)(&scodec->jack_mutex);
+
+ if (scodec->jack_status == SUN8I_JACK_STATUS_DISCONNECTED) {
+ if (scodec->last_hmic_irq != SUN8I_HMIC_STS_JACK_IN_IRQ_ST)
+ return;
+
+ scodec->jack_last_sample = -1;
+
+ if (type_mask & SND_JACK_MICROPHONE) {
+ /*
+ * If we were in disconnected state, we enable HBIAS and
+ * wait 600ms before reading initial HDATA value.
+ */
+ scodec->jack_hbias_ready = ktime_add_ms(ktime_get(), 600);
+ sun8i_codec_set_hmic_bias(scodec, true);
+ queue_delayed_work(system_power_efficient_wq,
+ &scodec->jack_work,
+ msecs_to_jiffies(610));
+ scodec->jack_status = SUN8I_JACK_STATUS_WAITING_HBIAS;
+ } else {
+ snd_soc_jack_report(scodec->jack, SND_JACK_HEADPHONE,
+ type_mask);
+ scodec->jack_status = SUN8I_JACK_STATUS_CONNECTED;
+ }
+ } else if (scodec->jack_status == SUN8I_JACK_STATUS_WAITING_HBIAS) {
+ /*
+ * If we're waiting for HBIAS to stabilize, and we get plug-out
+ * interrupt and nothing more for > 100ms, just cancel the
+ * initialization.
+ */
+ if (scodec->last_hmic_irq == SUN8I_HMIC_STS_JACK_OUT_IRQ_ST) {
+ scodec->jack_status = SUN8I_JACK_STATUS_DISCONNECTED;
+ sun8i_codec_set_hmic_bias(scodec, false);
+ return;
+ }
+
+ /*
+ * If we're not done waiting for HBIAS to stabilize, wait more.
+ */
+ if (!ktime_after(ktime_get(), scodec->jack_hbias_ready)) {
+ s64 msecs = ktime_ms_delta(scodec->jack_hbias_ready,
+ ktime_get());
+
+ queue_delayed_work(system_power_efficient_wq,
+ &scodec->jack_work,
+ msecs_to_jiffies(msecs + 10));
+ return;
+ }
+
+ /*
+ * Everything is stabilized, determine jack type and report it.
+ */
+ regmap_read(scodec->regmap, SUN8I_HMIC_STS, &mdata);
+ mdata &= SUN8I_HMIC_STS_HMIC_DATA_MASK;
+ mdata >>= SUN8I_HMIC_STS_HMIC_DATA;
+
+ regmap_write(scodec->regmap, SUN8I_HMIC_STS, 0);
+
+ type = mdata < 16 ? SND_JACK_HEADPHONE : SND_JACK_HEADSET;
+ if (type == SND_JACK_HEADPHONE)
+ sun8i_codec_set_hmic_bias(scodec, false);
+
+ snd_soc_jack_report(scodec->jack, type, type_mask);
+ scodec->jack_status = SUN8I_JACK_STATUS_CONNECTED;
+ } else if (scodec->jack_status == SUN8I_JACK_STATUS_CONNECTED) {
+ if (scodec->last_hmic_irq != SUN8I_HMIC_STS_JACK_OUT_IRQ_ST)
+ return;
+
+ scodec->jack_status = SUN8I_JACK_STATUS_DISCONNECTED;
+ if (type_mask & SND_JACK_MICROPHONE)
+ sun8i_codec_set_hmic_bias(scodec, false);
+
+ snd_soc_jack_report(scodec->jack, 0, type_mask);
+ }
+}
+
+static irqreturn_t sun8i_codec_jack_irq(int irq, void *dev_id)
+{
+ struct sun8i_codec *scodec = dev_id;
+ int type = SND_JACK_HEADSET;
+ unsigned int status, value;
+
+ guard(mutex)(&scodec->jack_mutex);
+
+ regmap_read(scodec->regmap, SUN8I_HMIC_STS, &status);
+ regmap_write(scodec->regmap, SUN8I_HMIC_STS, status);
+
+ /*
+ * De-bounce in/out interrupts via a delayed work re-scheduling to
+ * 100ms after each interrupt..
+ */
+ if (status & BIT(SUN8I_HMIC_STS_JACK_OUT_IRQ_ST)) {
+ /*
+ * Out interrupt has priority over in interrupt so that if
+ * we get both, we assume the disconnected state, which is
+ * safer.
+ */
+ scodec->last_hmic_irq = SUN8I_HMIC_STS_JACK_OUT_IRQ_ST;
+ mod_delayed_work(system_power_efficient_wq, &scodec->jack_work,
+ msecs_to_jiffies(100));
+ } else if (status & BIT(SUN8I_HMIC_STS_JACK_IN_IRQ_ST)) {
+ scodec->last_hmic_irq = SUN8I_HMIC_STS_JACK_IN_IRQ_ST;
+ mod_delayed_work(system_power_efficient_wq, &scodec->jack_work,
+ msecs_to_jiffies(100));
+ } else if (status & BIT(SUN8I_HMIC_STS_HMIC_DATA_IRQ_ST)) {
+ /*
+ * Ignore data interrupts until jack status turns to connected
+ * state, which is after HMIC enable stabilization is completed.
+ * Until then tha data are bogus.
+ */
+ if (scodec->jack_status != SUN8I_JACK_STATUS_CONNECTED)
+ return IRQ_HANDLED;
+
+ value = (status & SUN8I_HMIC_STS_HMIC_DATA_MASK) >>
+ SUN8I_HMIC_STS_HMIC_DATA;
+
+ /*
+ * Assumes 60 mV per ADC LSB increment, 2V bias voltage, 2.2kOhm
+ * bias resistor.
+ */
+ if (value == 0)
+ type |= SND_JACK_BTN_0;
+ else if (value == 1)
+ type |= SND_JACK_BTN_3;
+ else if (value <= 3)
+ type |= SND_JACK_BTN_1;
+ else if (value <= 8)
+ type |= SND_JACK_BTN_2;
+
+ /*
+ * De-bounce. Only report button after two consecutive A/D
+ * samples are identical.
+ */
+ if (scodec->jack_last_sample >= 0 &&
+ scodec->jack_last_sample == value)
+ snd_soc_jack_report(scodec->jack, type,
+ scodec->jack->jack->type);
+
+ scodec->jack_last_sample = value;
+ }
+
+ return IRQ_HANDLED;
+}
+
+static int sun8i_codec_enable_jack_detect(struct snd_soc_component *component,
+ struct snd_soc_jack *jack, void *data)
+{
+ struct sun8i_codec *scodec = snd_soc_component_get_drvdata(component);
+ struct platform_device *pdev = to_platform_device(component->dev);
+ int ret;
+
+ if (!scodec->quirks->jack_detection)
+ return 0;
+
+ scodec->jack = jack;
+
+ scodec->jack_irq = platform_get_irq(pdev, 0);
+ if (scodec->jack_irq < 0)
+ return scodec->jack_irq;
+
+ /* Reserved value required for jack IRQs to trigger. */
+ regmap_write(scodec->regmap, SUN8I_HMIC_CTRL1,
+ 0xf << SUN8I_HMIC_CTRL1_HMIC_N |
+ 0x0 << SUN8I_HMIC_CTRL1_MDATA_THRESHOLD_DB |
+ 0x4 << SUN8I_HMIC_CTRL1_HMIC_M);
+
+ /* Sample the ADC at 128 Hz; bypass smooth filter. */
+ regmap_write(scodec->regmap, SUN8I_HMIC_CTRL2,
+ 0x0 << SUN8I_HMIC_CTRL2_HMIC_SAMPLE |
+ 0x17 << SUN8I_HMIC_CTRL2_HMIC_MDATA_THRESHOLD |
+ 0x0 << SUN8I_HMIC_CTRL2_HMIC_SF);
+
+ /* Do not discard any MDATA, enable user written MDATA threshold. */
+ regmap_write(scodec->regmap, SUN8I_HMIC_STS, 0);
+
+ regmap_set_bits(scodec->regmap, SUN8I_HMIC_CTRL1,
+ BIT(SUN8I_HMIC_CTRL1_JACK_OUT_IRQ_EN) |
+ BIT(SUN8I_HMIC_CTRL1_JACK_IN_IRQ_EN));
+
+ ret = devm_request_threaded_irq(&pdev->dev, scodec->jack_irq,
+ NULL, sun8i_codec_jack_irq,
+ IRQF_ONESHOT,
+ dev_name(&pdev->dev), scodec);
+ if (ret)
+ return ret;
+
+ return 0;
+}
+
+static void sun8i_codec_disable_jack_detect(struct snd_soc_component *component)
+{
+ struct sun8i_codec *scodec = snd_soc_component_get_drvdata(component);
+
+ if (!scodec->quirks->jack_detection)
+ return;
+
+ devm_free_irq(component->dev, scodec->jack_irq, scodec);
+
+ cancel_delayed_work_sync(&scodec->jack_work);
+
+ regmap_clear_bits(scodec->regmap, SUN8I_HMIC_CTRL1,
+ BIT(SUN8I_HMIC_CTRL1_JACK_OUT_IRQ_EN) |
+ BIT(SUN8I_HMIC_CTRL1_JACK_IN_IRQ_EN) |
+ BIT(SUN8I_HMIC_CTRL1_HMIC_DATA_IRQ_EN));
+
+ scodec->jack = NULL;
+}
+
+static int sun8i_codec_component_set_jack(struct snd_soc_component *component,
+ struct snd_soc_jack *jack, void *data)
+{
+ int ret = 0;
+
+ if (jack)
+ ret = sun8i_codec_enable_jack_detect(component, jack, data);
+ else
+ sun8i_codec_disable_jack_detect(component);
+
+ return ret;
+}
+
static const struct snd_soc_component_driver sun8i_soc_component = {
.controls = sun8i_codec_controls,
.num_controls = ARRAY_SIZE(sun8i_codec_controls),
@@ -1288,16 +1583,23 @@ static const struct snd_soc_component_driver sun8i_soc_component = {
.num_dapm_widgets = ARRAY_SIZE(sun8i_codec_dapm_widgets),
.dapm_routes = sun8i_codec_dapm_routes,
.num_dapm_routes = ARRAY_SIZE(sun8i_codec_dapm_routes),
+ .set_jack = sun8i_codec_component_set_jack,
.probe = sun8i_codec_component_probe,
.idle_bias_on = 1,
.suspend_bias_off = 1,
.endianness = 1,
};
+static bool sun8i_codec_volatile_reg(struct device *dev, unsigned int reg)
+{
+ return reg == SUN8I_HMIC_STS;
+}
+
static const struct regmap_config sun8i_codec_regmap_config = {
.reg_bits = 32,
.reg_stride = 4,
.val_bits = 32,
+ .volatile_reg = sun8i_codec_volatile_reg,
.max_register = SUN8I_DAC_MXR_SRC,
.cache_type = REGCACHE_FLAT,
@@ -1314,6 +1616,8 @@ static int sun8i_codec_probe(struct platform_device *pdev)
return -ENOMEM;
scodec->quirks = of_device_get_match_data(&pdev->dev);
+ INIT_DELAYED_WORK(&scodec->jack_work, sun8i_codec_jack_work);
+ mutex_init(&scodec->jack_mutex);
platform_set_drvdata(pdev, scodec);
@@ -1387,6 +1691,7 @@ static const struct sun8i_codec_quirks sun8i_a33_quirks = {
static const struct sun8i_codec_quirks sun50i_a64_quirks = {
.bus_clock = true,
+ .jack_detection = true,
};
static const struct of_device_id sun8i_codec_of_match[] = {
--
2.44.0
next prev parent reply other threads:[~2024-03-02 14:00 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-02 14:00 [PATCH v3 0/4] Add support for jack detection to codec present in A64 SoC Ondřej Jirman
2024-03-02 14:00 ` [PATCH v3 1/4] ASoC: sun50i-codec-analog: Move suspend/resume to set_bias_level Ondřej Jirman
2024-03-02 14:00 ` [PATCH v3 2/4] ASoC: sun8i-codec: Enable bus clock at STANDBY and higher bias Ondřej Jirman
2024-03-02 14:00 ` [PATCH v3 3/4] ASoC: sun50i-codec-analog: Enable jack detection on startup Ondřej Jirman
2024-03-02 14:00 ` Ondřej Jirman [this message]
2024-03-26 15:27 ` [PATCH v3 0/4] Add support for jack detection to codec present in A64 SoC Mark Brown
2024-03-26 16:33 ` Ondřej Jirman
2024-03-26 16:46 ` Mark Brown
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20240302140042.1990256-5-megi@xff.cz \
--to=megi@xff.cz \
--cc=arnaud.ferraris@collabora.com \
--cc=broonie@kernel.org \
--cc=jernej.skrabec@gmail.com \
--cc=lgirdwood@gmail.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-sound@vger.kernel.org \
--cc=linux-sunxi@lists.linux.dev \
--cc=perex@perex.cz \
--cc=samuel@sholland.org \
--cc=tiwai@suse.com \
--cc=wens@csie.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).