All of lore.kernel.org
 help / color / mirror / Atom feed
From: Even Xu <even.xu@intel.com>
To: jikos@kernel.org, bentiss@kernel.org, corbet@lwn.net,
	bagasdotme@gmail.com, aaron.ma@canonical.com
Cc: linux-input@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-doc@vger.kernel.org, Xinpeng Sun <xinpeng.sun@intel.com>,
	Even Xu <even.xu@intel.com>, Rui Zhang <rui1.zhang@intel.com>,
	Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Subject: [PATCH v2 09/22] HID: intel-thc-hid: intel-thc: Add THC SPI config interfaces
Date: Thu, 14 Nov 2024 13:34:03 +0800	[thread overview]
Message-ID: <20241114053416.4085715-10-even.xu@intel.com> (raw)
In-Reply-To: <20241114053416.4085715-1-even.xu@intel.com>

From: Xinpeng Sun <xinpeng.sun@intel.com>

Add SPI bus related APIs to configure SPI operation parameters,
such as port type, bus frequency, bus IO mode, read/write OPcode,
and slave register addresses.

Co-developed-by: Even Xu <even.xu@intel.com>
Signed-off-by: Even Xu <even.xu@intel.com>
Signed-off-by: Xinpeng Sun <xinpeng.sun@intel.com>
Tested-by: Rui Zhang <rui1.zhang@intel.com>
Reviewed-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
---
 .../intel-thc-hid/intel-thc/intel-thc-dev.c   | 229 ++++++++++++++++++
 .../intel-thc-hid/intel-thc/intel-thc-dev.h   |   7 +
 .../intel-thc-hid/intel-thc/intel-thc-hw.h    |  52 ++++
 3 files changed, 288 insertions(+)

diff --git a/drivers/hid/intel-thc-hid/intel-thc/intel-thc-dev.c b/drivers/hid/intel-thc-hid/intel-thc/intel-thc-dev.c
index fb5d42cb1d44..4f1f86b45513 100644
--- a/drivers/hid/intel-thc-hid/intel-thc/intel-thc-dev.c
+++ b/drivers/hid/intel-thc-hid/intel-thc/intel-thc-dev.c
@@ -929,6 +929,235 @@ int thc_interrupt_handler(struct thc_device *dev)
 }
 EXPORT_SYMBOL_NS_GPL(thc_interrupt_handler, INTEL_THC);
 
+/**
+ * thc_port_select - Set THC port type
+ *
+ * @dev: The pointer of THC private device context
+ * @port_type: THC port type to use for current device
+ *
+ * Return: 0 on success, other error codes on failed.
+ */
+int thc_port_select(struct thc_device *dev, enum thc_port_type port_type)
+{
+	u32 ctrl, mask;
+
+	if (port_type == THC_PORT_TYPE_SPI) {
+		dev_dbg(dev->dev, "Set THC port type to SPI\n");
+		dev->port_type = THC_PORT_TYPE_SPI;
+
+		/* Enable delay of CS assertion and set to default value */
+		ctrl = THC_M_PRT_SPI_DUTYC_CFG_SPI_CSA_CK_DELAY_EN |
+		       FIELD_PREP(THC_M_PRT_SPI_DUTYC_CFG_SPI_CSA_CK_DELAY_VAL,
+				  THC_CSA_CK_DELAY_VAL_DEFAULT);
+		mask = THC_M_PRT_SPI_DUTYC_CFG_SPI_CSA_CK_DELAY_EN |
+		       THC_M_PRT_SPI_DUTYC_CFG_SPI_CSA_CK_DELAY_VAL;
+		regmap_write_bits(dev->thc_regmap, THC_M_PRT_SPI_DUTYC_CFG_OFFSET,
+				  mask, ctrl);
+	} else if (port_type == THC_PORT_TYPE_I2C) {
+		dev_dbg(dev->dev, "Set THC port type to I2C\n");
+		dev->port_type = THC_PORT_TYPE_I2C;
+
+		/* Set THC transition arbitration policy to frame boundary for I2C */
+		ctrl = FIELD_PREP(THC_M_PRT_CONTROL_THC_ARB_POLICY,
+				  THC_ARB_POLICY_FRAME_BOUNDARY);
+		mask = THC_M_PRT_CONTROL_THC_ARB_POLICY;
+
+		regmap_write_bits(dev->thc_regmap, THC_M_PRT_CONTROL_OFFSET, mask, ctrl);
+	} else {
+		dev_err(dev->dev, "unsupported THC port type: %d\n", port_type);
+		return -EINVAL;
+	}
+
+	ctrl = FIELD_PREP(THC_M_PRT_CONTROL_PORT_TYPE, port_type);
+	mask = THC_M_PRT_CONTROL_PORT_TYPE;
+
+	regmap_write_bits(dev->thc_regmap, THC_M_PRT_CONTROL_OFFSET, mask, ctrl);
+
+	return 0;
+}
+EXPORT_SYMBOL_NS_GPL(thc_port_select, INTEL_THC);
+
+#define THC_SPI_FREQUENCY_7M	7812500
+#define THC_SPI_FREQUENCY_15M	15625000
+#define THC_SPI_FREQUENCY_17M	17857100
+#define THC_SPI_FREQUENCY_20M	20833000
+#define THC_SPI_FREQUENCY_25M	25000000
+#define THC_SPI_FREQUENCY_31M	31250000
+#define THC_SPI_FREQUENCY_41M	41666700
+
+#define THC_SPI_LOW_FREQUENCY	THC_SPI_FREQUENCY_17M
+
+static u8 thc_get_spi_freq_div_val(struct thc_device *dev, u32 spi_freq_val)
+{
+	int frequency[] = {
+		THC_SPI_FREQUENCY_7M,
+		THC_SPI_FREQUENCY_15M,
+		THC_SPI_FREQUENCY_17M,
+		THC_SPI_FREQUENCY_20M,
+		THC_SPI_FREQUENCY_25M,
+		THC_SPI_FREQUENCY_31M,
+		THC_SPI_FREQUENCY_41M,
+	};
+	u8 frequency_div[] = {
+		THC_SPI_FRQ_DIV_2,
+		THC_SPI_FRQ_DIV_1,
+		THC_SPI_FRQ_DIV_7,
+		THC_SPI_FRQ_DIV_6,
+		THC_SPI_FRQ_DIV_5,
+		THC_SPI_FRQ_DIV_4,
+		THC_SPI_FRQ_DIV_3,
+	};
+	int size = ARRAY_SIZE(frequency);
+	u32 closest_freq;
+	u8 freq_div;
+	int i;
+
+	for (i = size - 1; i >= 0; i--)
+		if ((int)spi_freq_val - frequency[i] >= 0)
+			break;
+
+	if (i < 0) {
+		dev_err_once(dev->dev, "Not supported SPI frequency %d\n", spi_freq_val);
+		return THC_SPI_FRQ_RESERVED;
+	}
+
+	closest_freq = frequency[i];
+	freq_div = frequency_div[i];
+
+	dev_dbg(dev->dev,
+		"Setting SPI frequency: spi_freq_val = %u, Closest freq = %u\n",
+		spi_freq_val, closest_freq);
+
+	return freq_div;
+}
+
+/**
+ * thc_spi_read_config - Configure SPI bus read attributes
+ *
+ * @dev: The pointer of THC private device context
+ * @spi_freq_val: SPI read frequecy value
+ * @io_mode: SPI read IO mode
+ * @opcode: Read opcode
+ * @spi_rd_mps: SPI read max packet size
+ *
+ * Return: 0 on success, other error codes on failed.
+ */
+int thc_spi_read_config(struct thc_device *dev, u32 spi_freq_val,
+			u32 io_mode, u32 opcode, u32 spi_rd_mps)
+{
+	bool is_low_freq = false;
+	u32 cfg, mask;
+	u8 freq_div;
+
+	freq_div = thc_get_spi_freq_div_val(dev, spi_freq_val);
+	if (freq_div == THC_SPI_FRQ_RESERVED)
+		return -EINVAL;
+
+	if (spi_freq_val < THC_SPI_LOW_FREQUENCY)
+		is_low_freq = true;
+
+	cfg = FIELD_PREP(THC_M_PRT_SPI_CFG_SPI_TCRF, freq_div) |
+	      FIELD_PREP(THC_M_PRT_SPI_CFG_SPI_TRMODE, io_mode) |
+	      (is_low_freq ? THC_M_PRT_SPI_CFG_SPI_LOW_FREQ_EN : 0) |
+	      FIELD_PREP(THC_M_PRT_SPI_CFG_SPI_RD_MPS, spi_rd_mps);
+	mask = THC_M_PRT_SPI_CFG_SPI_TCRF |
+	       THC_M_PRT_SPI_CFG_SPI_TRMODE |
+	       THC_M_PRT_SPI_CFG_SPI_LOW_FREQ_EN |
+	       THC_M_PRT_SPI_CFG_SPI_RD_MPS;
+
+	regmap_write_bits(dev->thc_regmap,
+			  THC_M_PRT_SPI_CFG_OFFSET, mask, cfg);
+
+	if (io_mode == THC_QUAD_IO)
+		opcode = FIELD_PREP(THC_M_PRT_SPI_ICRRD_OPCODE_SPI_QIO, opcode);
+	else if (io_mode == THC_DUAL_IO)
+		opcode = FIELD_PREP(THC_M_PRT_SPI_ICRRD_OPCODE_SPI_DIO, opcode);
+	else
+		opcode = FIELD_PREP(THC_M_PRT_SPI_ICRRD_OPCODE_SPI_SIO, opcode);
+
+	regmap_write(dev->thc_regmap, THC_M_PRT_SPI_ICRRD_OPCODE_OFFSET, opcode);
+	regmap_write(dev->thc_regmap, THC_M_PRT_SPI_DMARD_OPCODE_OFFSET, opcode);
+
+	return 0;
+}
+EXPORT_SYMBOL_NS_GPL(thc_spi_read_config, INTEL_THC);
+
+/**
+ * thc_spi_write_config - Configure SPI bus write attributes
+ *
+ * @dev: The pointer of THC private device context
+ * @spi_freq_val: SPI write frequecy value
+ * @io_mode: SPI write IO mode
+ * @opcode: Write opcode
+ * @spi_wr_mps: SPI write max packet size
+ * @perf_limit: Performance limitation in unit of 10us
+ *
+ * Return: 0 on success, other error codes on failed.
+ */
+int thc_spi_write_config(struct thc_device *dev, u32 spi_freq_val,
+			 u32 io_mode, u32 opcode, u32 spi_wr_mps,
+			 u32 perf_limit)
+{
+	bool is_low_freq = false;
+	u32 cfg, mask;
+	u8 freq_div;
+
+	freq_div = thc_get_spi_freq_div_val(dev, spi_freq_val);
+	if (freq_div == THC_SPI_FRQ_RESERVED)
+		return -EINVAL;
+
+	if (spi_freq_val < THC_SPI_LOW_FREQUENCY)
+		is_low_freq = true;
+
+	cfg = FIELD_PREP(THC_M_PRT_SPI_CFG_SPI_TCWF, freq_div) |
+	      FIELD_PREP(THC_M_PRT_SPI_CFG_SPI_TWMODE, io_mode) |
+	      (is_low_freq ? THC_M_PRT_SPI_CFG_SPI_LOW_FREQ_EN : 0) |
+	      FIELD_PREP(THC_M_PRT_SPI_CFG_SPI_WR_MPS, spi_wr_mps);
+	mask = THC_M_PRT_SPI_CFG_SPI_TCWF |
+	       THC_M_PRT_SPI_CFG_SPI_TWMODE |
+	       THC_M_PRT_SPI_CFG_SPI_LOW_FREQ_EN |
+	       THC_M_PRT_SPI_CFG_SPI_WR_MPS;
+
+	regmap_write_bits(dev->thc_regmap,
+			  THC_M_PRT_SPI_CFG_OFFSET, mask, cfg);
+
+	if (io_mode == THC_QUAD_IO)
+		opcode = FIELD_PREP(THC_M_PRT_SPI_ICRRD_OPCODE_SPI_QIO, opcode);
+	else if (io_mode == THC_DUAL_IO)
+		opcode = FIELD_PREP(THC_M_PRT_SPI_ICRRD_OPCODE_SPI_DIO, opcode);
+	else
+		opcode = FIELD_PREP(THC_M_PRT_SPI_ICRRD_OPCODE_SPI_SIO, opcode);
+
+	regmap_write(dev->thc_regmap, THC_M_PRT_SPI_WR_OPCODE_OFFSET, opcode);
+
+	dev->perf_limit = perf_limit;
+
+	return 0;
+}
+EXPORT_SYMBOL_NS_GPL(thc_spi_write_config, INTEL_THC);
+
+/**
+ * thc_spi_input_output_address_config - Configure SPI input and output addresses
+ *
+ * @dev: the pointer of THC private device context
+ * @input_hdr_addr: input report header address
+ * @input_bdy_addr: input report body address
+ * @output_addr: output report address
+ */
+void thc_spi_input_output_address_config(struct thc_device *dev, u32 input_hdr_addr,
+					 u32 input_bdy_addr, u32 output_addr)
+{
+	regmap_write(dev->thc_regmap,
+		     THC_M_PRT_DEV_INT_CAUSE_ADDR_OFFSET, input_hdr_addr);
+	regmap_write(dev->thc_regmap,
+		     THC_M_PRT_RD_BULK_ADDR_1_OFFSET, input_bdy_addr);
+	regmap_write(dev->thc_regmap,
+		     THC_M_PRT_RD_BULK_ADDR_2_OFFSET, input_bdy_addr);
+	regmap_write(dev->thc_regmap,
+		     THC_M_PRT_WR_BULK_ADDR_OFFSET, output_addr);
+}
+EXPORT_SYMBOL_NS_GPL(thc_spi_input_output_address_config, INTEL_THC);
+
 MODULE_AUTHOR("Xinpeng Sun <xinpeng.sun@intel.com>");
 MODULE_AUTHOR("Even Xu <even.xu@intel.com>");
 
diff --git a/drivers/hid/intel-thc-hid/intel-thc/intel-thc-dev.h b/drivers/hid/intel-thc-hid/intel-thc/intel-thc-dev.h
index d34fab243fdc..925355f19bae 100644
--- a/drivers/hid/intel-thc-hid/intel-thc/intel-thc-dev.h
+++ b/drivers/hid/intel-thc-hid/intel-thc/intel-thc-dev.h
@@ -98,5 +98,12 @@ void thc_change_ltr_mode(struct thc_device *dev, u32 ltr_mode);
 void thc_ltr_unconfig(struct thc_device *dev);
 u32 thc_int_cause_read(struct thc_device *dev);
 int thc_interrupt_handler(struct thc_device *dev);
+int thc_port_select(struct thc_device *dev, enum thc_port_type port_type);
+int thc_spi_read_config(struct thc_device *dev, u32 spi_freq_val,
+			u32 io_mode, u32 opcode, u32 spi_rd_mps);
+int thc_spi_write_config(struct thc_device *dev, u32 spi_freq_val,
+			 u32 io_mode, u32 opcode, u32 spi_wr_mps, u32 perf_limit);
+void thc_spi_input_output_address_config(struct thc_device *dev, u32 input_hdr_addr,
+					 u32 input_bdy_addr, u32 output_addr);
 
 #endif /* _INTEL_THC_DEV_H_ */
diff --git a/drivers/hid/intel-thc-hid/intel-thc/intel-thc-hw.h b/drivers/hid/intel-thc-hid/intel-thc/intel-thc-hw.h
index 4a1153022605..985cad0cbe87 100644
--- a/drivers/hid/intel-thc-hid/intel-thc/intel-thc-hw.h
+++ b/drivers/hid/intel-thc-hid/intel-thc/intel-thc-hw.h
@@ -633,6 +633,20 @@
 
 #define THC_M_PRT_SW_DMA_PRD_TABLE_LEN_THC_M_PRT_SW_DMA_PRD_TABLE_LEN	GENMASK(23, 0)
 
+#define THC_M_PRT_SPI_DUTYC_CFG_SPI_CSA_CK_DELAY_VAL		GENMASK(3, 0)
+#define THC_M_PRT_SPI_DUTYC_CFG_SPI_CSA_CK_DELAY_EN		BIT(25)
+
+/* CS Assertion delay default value */
+#define THC_CSA_CK_DELAY_VAL_DEFAULT		4
+
+/* ARB policy definition */
+/* Arbiter switches on packet boundary */
+#define THC_ARB_POLICY_PACKET_BOUNDARY		0
+/* Arbiter switches on Micro Frame boundary */
+#define THC_ARB_POLICY_UFRAME_BOUNDARY		1
+/* Arbiter switches on Frame boundary */
+#define THC_ARB_POLICY_FRAME_BOUNDARY		2
+
 #define THC_REGMAP_POLLING_INTERVAL_US		10 /* 10us */
 #define THC_PIO_DONE_TIMEOUT_US			USEC_PER_SEC /* 1s */
 
@@ -694,4 +708,42 @@ enum thc_pio_opcode {
 	THC_PIO_OP_I2C_TIC_WRITE_AND_READ = 0x1C,
 };
 
+/**
+ * THC SPI IO mode
+ * @THC_SINGLE_IO: single IO mode, 1(opcode) - 1(address) - 1(data)
+ * @THC_DUAL_IO: dual IO mode, 1(opcode) - 2(address) - 2(data)
+ * @THC_QUAD_IO: quad IO mode, 1(opcode) - 4(address) - 4(data)
+ * @THC_QUAD_PARALLEL_IO: parallel quad IO mode, 4(opcode) - 4(address) - 4(data)
+ */
+enum thc_spi_iomode {
+	THC_SINGLE_IO = 0,
+	THC_DUAL_IO = 1,
+	THC_QUAD_IO = 2,
+	THC_QUAD_PARALLEL_IO = 3,
+};
+
+/**
+ * THC SPI frequency divider
+ *
+ * This DIV final value is determined by THC_M_PRT_SPI_CFG_SPI_LOW_FREQ_EN bit.
+ * If THC_M_PRT_SPI_CFG_SPI_LOW_FREQ_EN isn't be set, THC takes the DIV value directly;
+ * If THC_M_PRT_SPI_CFG_SPI_LOW_FREQ_EN is set, THC takes the DIV value multiply by 8.
+ *
+ * For example, if THC input clock is 125MHz:
+ * When THC_M_PRT_SPI_CFG_SPI_LOW_FREQ_EN isn't set, THC_SPI_FRQ_DIV_3 means DIV is 3,
+ * THC final clock is 125 / 3 = 41.667MHz;
+ * When THC_M_PRT_SPI_CFG_SPI_LOW_FREQ_EN is set, THC_SPI_FRQ_DIV_3 means DIV is 3 * 8,
+ * THC final clock is 125 / (3 * 8) = 5.208MHz;
+ */
+enum thc_spi_frq_div {
+	THC_SPI_FRQ_RESERVED = 0,
+	THC_SPI_FRQ_DIV_1 = 1,
+	THC_SPI_FRQ_DIV_2 = 2,
+	THC_SPI_FRQ_DIV_3 = 3,
+	THC_SPI_FRQ_DIV_4 = 4,
+	THC_SPI_FRQ_DIV_5 = 5,
+	THC_SPI_FRQ_DIV_6 = 6,
+	THC_SPI_FRQ_DIV_7 = 7,
+};
+
 #endif /* _INTEL_THC_HW_H_  */
-- 
2.40.1


  parent reply	other threads:[~2024-11-14  5:34 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-11-14  5:33 [PATCH v2 00/22] Add Intel Touch Host Controller drivers Even Xu
2024-11-14  5:33 ` [PATCH v2 01/22] HID: THC: Add documentation Even Xu
2024-11-14 13:16   ` Srinivas Pandruvada
2024-11-15  0:39     ` Xu, Even
2024-11-15  4:04   ` Bagas Sanjaya
2024-11-15  5:10     ` Xu, Even
2024-11-15 11:38       ` Bagas Sanjaya
2024-11-18  0:34         ` Xu, Even
2024-11-14  5:33 ` [PATCH v2 02/22] HID: intel-thc-hid: Add basic THC driver skeleton Even Xu
2024-11-14  5:41   ` Randy Dunlap
2024-11-14  5:56     ` Xu, Even
2024-11-14  5:33 ` [PATCH v2 03/22] HID: intel-thc-hid: intel-thc: Add THC registers definition Even Xu
2024-11-14  5:33 ` [PATCH v2 04/22] HID: intel-thc-hid: intel-thc: Add THC PIO operation APIs Even Xu
2024-12-04  5:37   ` Aaron Ma
2024-12-04  6:00     ` Xu, Even
2024-11-14  5:33 ` [PATCH v2 05/22] HID: intel-thc-hid: intel-thc: Add APIs for interrupt Even Xu
2024-11-14  5:34 ` [PATCH v2 06/22] HID: intel-thc-hid: intel-thc: Add THC DMA interfaces Even Xu
2024-11-14  5:34 ` [PATCH v2 07/22] HID: intel-thc-hid: intel-thc: Add THC LTR interfaces Even Xu
2024-11-14  5:34 ` [PATCH v2 08/22] HID: intel-thc-hid: intel-thc: Add THC interrupt handler Even Xu
2024-11-14  5:34 ` Even Xu [this message]
2024-11-14  5:34 ` [PATCH v2 10/22] HID: intel-thc-hid: intel-thc: Add THC I2C config interfaces Even Xu
2024-11-14  5:34 ` [PATCH v2 11/22] HID: intel-thc-hid: intel-quickspi: Add THC QuickSPI driver skeleton Even Xu
2024-11-14  5:44   ` Randy Dunlap
2024-11-14  5:59     ` Xu, Even
2024-11-14  5:34 ` [PATCH v2 12/22] HID: intel-thc-hid: intel-quickspi: Add THC QuickSPI driver hid layer Even Xu
2024-11-14  5:34 ` [PATCH v2 13/22] HID: intel-thc-hid: intel-quickspi: Add THC QuickSPI ACPI interfaces Even Xu
2024-11-14  5:34 ` [PATCH v2 14/22] HID: intel-thc-hid: intel-quickspi: Add HIDSPI protocol implementation Even Xu
2024-11-14  5:34 ` [PATCH v2 15/22] HID: intel-thc-hid: intel-quickspi: Complete THC QuickSPI driver Even Xu
2024-11-14  5:34 ` [PATCH v2 16/22] HID: intel-thc-hid: intel-quickspi: Add PM implementation Even Xu
2024-11-14  5:34 ` [PATCH v2 17/22] HID: intel-thc-hid: intel-quicki2c: Add THC QuickI2C driver skeleton Even Xu
2024-11-14  5:45   ` Randy Dunlap
2024-11-14  6:01     ` Xu, Even
2024-11-14  5:34 ` [PATCH v2 18/22] HID: intel-thc-hid: intel-quicki2c: Add THC QuickI2C driver hid layer Even Xu
2024-11-14  5:34 ` [PATCH v2 19/22] HID: intel-thc-hid: intel-quicki2c: Add THC QuickI2C ACPI interfaces Even Xu
2024-11-14  5:34 ` [PATCH v2 20/22] HID: intel-thc-hid: intel-quicki2c: Add HIDI2C protocol implementation Even Xu
2024-11-14  5:34 ` [PATCH v2 21/22] HID: intel-thc-hid: intel-quicki2c: Complete THC QuickI2C driver Even Xu
2024-11-14  5:34 ` [PATCH v2 22/22] HID: intel-thc-hid: intel-quicki2c: Add PM implementation Even Xu

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=20241114053416.4085715-10-even.xu@intel.com \
    --to=even.xu@intel.com \
    --cc=aaron.ma@canonical.com \
    --cc=bagasdotme@gmail.com \
    --cc=bentiss@kernel.org \
    --cc=corbet@lwn.net \
    --cc=jikos@kernel.org \
    --cc=linux-doc@vger.kernel.org \
    --cc=linux-input@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=rui1.zhang@intel.com \
    --cc=srinivas.pandruvada@linux.intel.com \
    --cc=xinpeng.sun@intel.com \
    /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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.