From: Ganapathi Bhat <gbhat@xxxxxxxxxxx> This patch implement firmware download feature for Marvell Bluetooth devices. If firmware is already downloaded, it will skip downloading. Signed-off-by: Ganapathi Bhat <gbhat@xxxxxxxxxxx> Signed-off-by: Amitkumar Karwar <akarwar@xxxxxxxxxxx> --- v2: Fixed compilation warning reported by kbuild test robot v3: Addressed review comments from Marcel Holtmann a) Removed vendor specific code from hci_ldisc.c b) Get rid of static forward declaration c) Removed unnecessary heavy nesting d) Git rid of module parameter and global variables e) Add logic to pick right firmware image v4: Addresses review comments from Alan a) Use existing kernel helper APIs instead of writing own. b) Replace mdelay() with msleep() --- drivers/bluetooth/Kconfig | 10 + drivers/bluetooth/Makefile | 1 + drivers/bluetooth/btmrvl.h | 41 +++ drivers/bluetooth/hci_ldisc.c | 6 + drivers/bluetooth/hci_mrvl.c | 585 ++++++++++++++++++++++++++++++++++++++++++ drivers/bluetooth/hci_uart.h | 13 +- 6 files changed, 655 insertions(+), 1 deletion(-) create mode 100644 drivers/bluetooth/btmrvl.h create mode 100644 drivers/bluetooth/hci_mrvl.c diff --git a/drivers/bluetooth/Kconfig b/drivers/bluetooth/Kconfig index cf50fd2..cb825f1 100644 --- a/drivers/bluetooth/Kconfig +++ b/drivers/bluetooth/Kconfig @@ -180,6 +180,16 @@ config BT_HCIUART_AG6XX Say Y here to compile support for Intel AG6XX protocol. +config BT_HCIUART_MRVL + bool "Marvell protocol support" + depends on BT_HCIUART + help + Marvell is serial protocol for communication between Bluetooth + device and host. This protocol is required for most Marvell Bluetooth + devices with UART interface. + + Say Y here to compile support for HCI MRVL protocol. + config BT_HCIBCM203X tristate "HCI BCM203x USB driver" depends on USB diff --git a/drivers/bluetooth/Makefile b/drivers/bluetooth/Makefile index 9c18939..364dbb6 100644 --- a/drivers/bluetooth/Makefile +++ b/drivers/bluetooth/Makefile @@ -37,6 +37,7 @@ hci_uart-$(CONFIG_BT_HCIUART_INTEL) += hci_intel.o hci_uart-$(CONFIG_BT_HCIUART_BCM) += hci_bcm.o hci_uart-$(CONFIG_BT_HCIUART_QCA) += hci_qca.o hci_uart-$(CONFIG_BT_HCIUART_AG6XX) += hci_ag6xx.o +hci_uart-$(CONFIG_BT_HCIUART_MRVL) += hci_mrvl.o hci_uart-objs := $(hci_uart-y) ccflags-y += -D__CHECK_ENDIAN__ diff --git a/drivers/bluetooth/btmrvl.h b/drivers/bluetooth/btmrvl.h new file mode 100644 index 0000000..fec87e2 --- /dev/null +++ b/drivers/bluetooth/btmrvl.h @@ -0,0 +1,41 @@ +/* Bluetooth support for Marvell devices + * + * Copyright (C) 2016, Marvell International Ltd. + * + * This software file (the "File") is distributed by Marvell International + * Ltd. under the terms of the GNU General Public License Version 2, June 1991 + * (the "License"). You may use, redistribute and/or modify this File in + * accordance with the terms and conditions of the License, a copy of which + * is available on the worldwide web at + * http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt. + * + * THE FILE IS DISTRIBUTED AS-IS, WITHOUT WARRANTY OF ANY KIND, AND THE + * IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE + * ARE EXPRESSLY DISCLAIMED. The License provides additional details about + * this warranty disclaimer. + */ + +struct fw_data { + wait_queue_head_t init_wait_q __aligned(4); + u8 wait_fw; + int next_len; + u8 five_bytes[5]; + u8 next_index; + u8 last_ack; + u8 expected_ack; + struct ktermios old_termios; + u8 chip_id; + u8 chip_rev; +}; + +#define MRVL_HELPER_NAME "mrvl/helper_uart_3000000.bin" +#define MRVL_8997_FW_NAME "mrvl/uart8997_bt.bin" +#define MRVL_WAIT_TIMEOUT 12000 +#define MRVL_MAX_FW_BLOCK_SIZE 1024 +#define MRVL_MAX_RETRY_SEND 12 +#define MRVL_DNLD_DELAY 100 +#define MRVL_ACK 0x5A +#define MRVL_NAK 0xBF +#define MRVL_HDR_REQ_FW 0xA5 +#define MRVL_HDR_CHIP_VER 0xAA +#define MRVL_HCI_OP_SET_BAUD 0xFC09 diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c index c00168a..b858758 100644 --- a/drivers/bluetooth/hci_ldisc.c +++ b/drivers/bluetooth/hci_ldisc.c @@ -807,6 +807,9 @@ static int __init hci_uart_init(void) #ifdef CONFIG_BT_HCIUART_AG6XX ag6xx_init(); #endif +#ifdef CONFIG_BT_HCIUART_MRVL + mrvl_init(); +#endif return 0; } @@ -842,6 +845,9 @@ static void __exit hci_uart_exit(void) #ifdef CONFIG_BT_HCIUART_AG6XX ag6xx_deinit(); #endif +#ifdef CONFIG_BT_HCIUART_MRVL + mrvl_deinit(); +#endif /* Release tty registration of line discipline */ err = tty_unregister_ldisc(N_HCI); diff --git a/drivers/bluetooth/hci_mrvl.c b/drivers/bluetooth/hci_mrvl.c new file mode 100644 index 0000000..686f6c2 --- /dev/null +++ b/drivers/bluetooth/hci_mrvl.c @@ -0,0 +1,585 @@ +/* Bluetooth HCI UART driver for Marvell devices + * + * Copyright (C) 2016, Marvell International Ltd. + * + * Acknowledgements: + * This file is based on hci_h4.c, which was written + * by Maxim Krasnyansky and Marcel Holtmann. + * + * This software file (the "File") is distributed by Marvell International + * Ltd. under the terms of the GNU General Public License Version 2, June 1991 + * (the "License"). You may use, redistribute and/or modify this File in + * accordance with the terms and conditions of the License, a copy of which + * is available on the worldwide web at + * http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt. + * + * THE FILE IS DISTRIBUTED AS-IS, WITHOUT WARRANTY OF ANY KIND, AND THE + * IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE + * ARE EXPRESSLY DISCLAIMED. The License provides additional details about + * this warranty disclaimer. + */ + +#include <linux/module.h> + +#include <linux/kernel.h> +#include <linux/init.h> +#include <linux/types.h> +#include <linux/fcntl.h> +#include <linux/interrupt.h> +#include <linux/ptrace.h> +#include <linux/poll.h> +#include <linux/firmware.h> +#include <linux/version.h> +#include <linux/slab.h> +#include <linux/tty.h> +#include <linux/errno.h> +#include <linux/string.h> +#include <linux/signal.h> +#include <linux/ioctl.h> +#include <linux/skbuff.h> +#include <asm/unaligned.h> + +#include <net/bluetooth/bluetooth.h> +#include <net/bluetooth/hci_core.h> + +#include "hci_uart.h" +#include "btmrvl.h" + +struct mrvl_data { + struct sk_buff *rx_skb; + struct sk_buff_head txq; + struct fw_data *fwdata; +}; + +/* Initialize protocol */ +static int mrvl_open(struct hci_uart *hu) +{ + struct mrvl_data *mrvl; + + BT_DBG("hu %p", hu); + + mrvl = kzalloc(sizeof(*mrvl), GFP_KERNEL); + if (!mrvl) + return -ENOMEM; + + skb_queue_head_init(&mrvl->txq); + hu->priv = mrvl; + + return 0; +} + +/* Flush protocol data */ +static int mrvl_flush(struct hci_uart *hu) +{ + struct mrvl_data *mrvl = hu->priv; + + BT_DBG("hu %p", hu); + + skb_queue_purge(&mrvl->txq); + + return 0; +} + +/* Close protocol */ +static int mrvl_close(struct hci_uart *hu) +{ + struct mrvl_data *mrvl = hu->priv; + + BT_DBG("hu %p", hu); + + skb_queue_purge(&mrvl->txq); + kfree_skb(mrvl->rx_skb); + kfree(mrvl->fwdata); + hu->priv = NULL; + kfree(mrvl); + + return 0; +} + +/* Enqueue frame for transmittion (padding, crc, etc) */ +static int mrvl_enqueue(struct hci_uart *hu, struct sk_buff *skb) +{ + struct mrvl_data *mrvl = hu->priv; + + if (test_bit(HCI_UART_DNLD_FW, &hu->flags)) + return -EBUSY; + + BT_DBG("hu %p skb %p", hu, skb); + + /* Prepend skb with frame type */ + memcpy(skb_push(skb, 1), &hci_skb_pkt_type(skb), 1); + skb_queue_tail(&mrvl->txq, skb); + + return 0; +} + +static const struct h4_recv_pkt mrvl_recv_pkts[] = { + { H4_RECV_ACL, .recv = hci_recv_frame }, + { H4_RECV_SCO, .recv = hci_recv_frame }, + { H4_RECV_EVENT, .recv = hci_recv_frame }, +}; + +/* Receive data */ +static int mrvl_recv(struct hci_uart *hu, const void *data, int count) +{ + struct mrvl_data *mrvl = hu->priv; + + if (test_bit(HCI_UART_DNLD_FW, &hu->flags)) { + hci_uart_recv_data(hu, (u8 *)data, count); + return 0; + } + + if (!test_bit(HCI_UART_REGISTERED, &hu->flags)) + return -EUNATCH; + + mrvl->rx_skb = h4_recv_buf(hu->hdev, mrvl->rx_skb, data, count, + mrvl_recv_pkts, ARRAY_SIZE(mrvl_recv_pkts)); + if (IS_ERR(mrvl->rx_skb)) { + int err = PTR_ERR(mrvl->rx_skb); + + BT_ERR("%s: Frame reassembly failed (%d)", hu->hdev->name, err); + mrvl->rx_skb = NULL; + return err; + } + + return count; +} + +static struct sk_buff *mrvl_dequeue(struct hci_uart *hu) +{ + struct mrvl_data *mrvl = hu->priv; + + return skb_dequeue(&mrvl->txq); +} + +static int mrvl_init_fw_data(struct hci_uart *hu) +{ + struct fw_data *fwdata; + struct mrvl_data *mrvl = hu->priv; + + fwdata = kzalloc(sizeof(*fwdata), GFP_KERNEL); + + if (!fwdata) { + BT_ERR("Can't allocate firmware data"); + return -ENOMEM; + } + + mrvl->fwdata = fwdata; + init_waitqueue_head(&fwdata->init_wait_q); + + return 0; +} + +static int mrvl_setup(struct hci_uart *hu) +{ + mrvl_init_fw_data(hu); + set_bit(HCI_UART_DNLD_FW, &hu->flags); + + return hci_uart_dnld_fw(hu); +} + +static const struct hci_uart_proto mrvlp = { + .id = HCI_UART_MRVL, + .name = "MRVL", + .open = mrvl_open, + .close = mrvl_close, + .recv = mrvl_recv, + .enqueue = mrvl_enqueue, + .dequeue = mrvl_dequeue, + .flush = mrvl_flush, + .setup = mrvl_setup, +}; + +int __init mrvl_init(void) +{ + return hci_uart_register_proto(&mrvlp); +} + +int __exit mrvl_deinit(void) +{ + return hci_uart_unregister_proto(&mrvlp); +} + +static int get_cts(struct tty_struct *tty) +{ + u32 state; + + if (tty->ops->tiocmget) { + state = tty->ops->tiocmget(tty); + if (state & TIOCM_CTS) { + BT_DBG("CTS is low"); + return 1; + } + BT_DBG("CTS is high"); + return 0; + } + return -1; +} + +/* Wait for the header from device */ +static int mrvl_wait_for_hdr(struct hci_uart *hu, u8 header) +{ + struct mrvl_data *mrvl = hu->priv; + struct fw_data *fw_data = mrvl->fwdata; + + fw_data->expected_ack = header; + fw_data->wait_fw = 0; + + if (!wait_event_interruptible_timeout(fw_data->init_wait_q, + fw_data->wait_fw, + ((MRVL_WAIT_TIMEOUT) * HZ / 1000))) { + BT_ERR("TIMEOUT, waiting for:0x%x", fw_data->expected_ack); + return -1; + } + + return 0; +} + +/* Send bytes to device */ +static int mrvl_send_data(struct hci_uart *hu, struct sk_buff *skb) +{ + struct tty_struct *tty = hu->tty; + int retry = 0; + int skb_len; + + skb_len = skb->len; + while (retry < MRVL_MAX_RETRY_SEND) { + tty->ops->write(tty, skb->data, skb->len); + if (mrvl_wait_for_hdr(hu, MRVL_HDR_REQ_FW) == -1) { + retry++; + continue; + } else { + skb_pull(skb, skb_len); + break; + } + } + if (retry == MRVL_MAX_RETRY_SEND) + return -1; + + return 0; +} + +/* Download firmware to the device */ +static int mrvl_dnld_fw(struct hci_uart *hu, const char *file_name) +{ + struct hci_dev *hdev = hu->hdev; + const struct firmware *fw; + struct sk_buff *skb = NULL; + int offset = 0; + int ret, tx_len; + struct mrvl_data *mrvl = hu->priv; + struct fw_data *fw_data = mrvl->fwdata; + + ret = request_firmware(&fw, file_name, &hdev->dev); + if (ret < 0) { + BT_ERR("request_firmware() failed"); + ret = -1; + goto done; + } + if (fw) { + BT_INFO("Downloading FW (%d bytes)", (u16)fw->size); + } else { + BT_ERR("No FW image found"); + ret = -1; + goto done; + } + + skb = bt_skb_alloc(MRVL_MAX_FW_BLOCK_SIZE, GFP_ATOMIC); + if (!skb) { + BT_ERR("cannot allocate memory for skb"); + ret = -1; + goto done; + } + + skb->dev = (void *)hdev; + fw_data->last_ack = 0; + + do { + if ((offset >= fw->size) || (fw_data->last_ack)) + break; + tx_len = fw_data->next_len; + if ((fw->size - offset) < tx_len) + tx_len = fw->size - offset; + + memcpy(skb->data, &fw->data[offset], tx_len); + skb_put(skb, tx_len); + if (mrvl_send_data(hu, skb) != 0) { + BT_ERR("fail to download firmware"); + ret = -1; + goto done; + } + skb_push(skb, tx_len); + skb_trim(skb, 0); + offset += tx_len; + } while (1); + + BT_INFO("downloaded %d byte firmware", offset); +done: + if (fw) + release_firmware(fw); + + kfree(skb); + return ret; +} + +/* Set the baud rate */ +static int mrvl_set_dev_baud(struct hci_uart *hu) +{ + struct hci_dev *hdev = hu->hdev; + struct sk_buff *skb; + static const u8 baud_param[] = { 0xc0, 0xc6, 0x2d, 0x00}; + int err; + + skb = __hci_cmd_sync(hdev, MRVL_HCI_OP_SET_BAUD, sizeof(baud_param), + baud_param, HCI_INIT_TIMEOUT); + if (IS_ERR(skb)) { + err = PTR_ERR(skb); + BT_ERR("%s: Set device baudrate failed (%d)", hdev->name, err); + return err; + } + kfree_skb(skb); + + return 0; +} + +/* Reset device */ +static int mrvl_reset(struct hci_uart *hu) +{ + struct hci_dev *hdev = hu->hdev; + struct sk_buff *skb; + int err; + + skb = __hci_cmd_sync(hdev, HCI_OP_RESET, 0, NULL, HCI_CMD_TIMEOUT); + if (IS_ERR(skb)) { + err = PTR_ERR(skb); + BT_ERR("%s: Reset device failed (%d)", hdev->name, err); + return err; + } + kfree_skb(skb); + + return 0; +} + +static int mrvl_set_baud(struct hci_uart *hu) +{ + int err; + + hci_uart_set_baudrate(hu, 115200); + hci_uart_set_flow_control(hu, false); + + err = mrvl_reset(hu); + if (err) + goto set_term_baud; + else + goto set_dev_baud; + +set_dev_baud: + err = mrvl_set_dev_baud(hu); + if (err) + return -1; + +set_term_baud: + hci_uart_set_baudrate(hu, 3000000); + hci_uart_set_flow_control(hu, false); + + return 0; +} + +static int mrvl_get_fw_name(struct hci_uart *hu, char *fw_name) +{ + int ret; + struct mrvl_data *mrvl = hu->priv; + struct fw_data *fw_data = mrvl->fwdata; + + ret = mrvl_wait_for_hdr(hu, MRVL_HDR_CHIP_VER); + if (ret) { + ret = -1; + BT_ERR("Could not read chip id and revision"); + goto fail; + } + + BT_DBG("chip_id=0x%x, chip_rev=0x%x", + fw_data->chip_id, fw_data->chip_rev); + + if (fw_data->chip_id == 0x50) { + memcpy(fw_name, MRVL_8997_FW_NAME, sizeof(MRVL_8997_FW_NAME)); + } else { + ret = -1; + BT_ERR("Invalid chip id"); + } +fail: + return ret; +} + +/* Download helper and firmare to device */ +int hci_uart_dnld_fw(struct hci_uart *hu) +{ + struct tty_struct *tty = hu->tty; + struct ktermios new_termios; + struct ktermios old_termios; + char fw_name[128]; + int ret; + + old_termios = tty->termios; + + if (!tty) { + BT_ERR("tty is null"); + clear_bit(HCI_UART_DNLD_FW, &hu->flags); + ret = -1; + goto fail; + } + + if (get_cts(hu->tty)) { + BT_INFO("fw is running"); + clear_bit(HCI_UART_DNLD_FW, &hu->flags); + goto set_baud; + } + + hci_uart_set_baudrate(hu, 115200); + hci_uart_set_flow_control(hu, true); + + ret = mrvl_wait_for_hdr(hu, MRVL_HDR_REQ_FW); + if (ret) + goto fail; + + ret = mrvl_dnld_fw(hu, MRVL_HELPER_NAME); + if (ret) + goto fail; + + msleep(MRVL_DNLD_DELAY); + + hci_uart_set_baudrate(hu, 3000000); + hci_uart_set_flow_control(hu, false); + + ret = mrvl_get_fw_name(hu, fw_name); + if (ret) + goto fail; + + ret = mrvl_wait_for_hdr(hu, MRVL_HDR_REQ_FW); + if (ret) + goto fail; + + ret = mrvl_dnld_fw(hu, fw_name); + if (ret) + goto fail; + + msleep(MRVL_DNLD_DELAY); + /* restore uart settings */ + new_termios = tty->termios; + tty->termios.c_cflag = old_termios.c_cflag; + tty_set_termios(tty, &new_termios); + clear_bit(HCI_UART_DNLD_FW, &hu->flags); + +set_baud: + ret = mrvl_set_baud(hu); + if (ret) + goto fail; + + msleep(MRVL_DNLD_DELAY); + + return ret; +fail: + /* restore uart settings */ + new_termios = tty->termios; + tty->termios.c_cflag = old_termios.c_cflag; + tty_set_termios(tty, &new_termios); + clear_bit(HCI_UART_DNLD_FW, &hu->flags); + + return ret; +} + +/* Send ACK/NAK to the device */ +static void mrvl_send_ack(struct hci_uart *hu, unsigned char ack) +{ + struct tty_struct *tty = hu->tty; + + tty->ops->write(tty, &ack, sizeof(ack)); +} + +/* Validate the feedback data from device */ +static void mrvl_validate_hdr_and_len(struct hci_uart *hu, u8 *buf) +{ + struct mrvl_data *mrvl = hu->priv; + struct fw_data *fw_data = mrvl->fwdata; + u16 lhs, rhs; + + lhs = le16_to_cpu(*((__le16 *)(&buf[1]))); + rhs = le16_to_cpu(*((__le16 *)(&buf[3]))); + if ((lhs ^ rhs) == 0xffff) { + mrvl_send_ack(hu, MRVL_ACK); + fw_data->wait_fw = 1; + fw_data->next_len = lhs; + /*firmware download is done, send the last ack*/ + if (!lhs) + fw_data->last_ack = 1; + + if (unlikely(fw_data->expected_ack == MRVL_HDR_CHIP_VER)) { + fw_data->chip_id = *((u8 *)(&buf[1])); + fw_data->chip_rev = *((u8 *)(&buf[2])); + } + wake_up_interruptible(&fw_data->init_wait_q); + } else { + mrvl_send_ack(hu, MRVL_NAK); + } +} + +void hci_uart_recv_data(struct hci_uart *hu, u8 *buf, int len) +{ + struct mrvl_data *mrvl = hu->priv; + struct fw_data *fw_data = mrvl->fwdata; + int i = 0; + + if (len < 5) { + if ((!fw_data->next_index) && + (buf[0] != fw_data->expected_ack)) { + /*ex: XX XX XX*/ + return; + } + } + + if (len == 5) { + if (buf[0] != fw_data->expected_ack) { + /*ex: XX XX XX XX XX*/ + return; + } + /*ex: 5A LL LL LL LL*/ + fw_data->next_index = 0; + mrvl_validate_hdr_and_len(hu, buf); + return; + } + + if (len > 5) { + i = 0; + + while ((i < len) && (buf[i] != fw_data->expected_ack)) + i++; + + if (i == len) { + /* Could not find a header */ + return; + } + + if ((len - i) >= 5) { + /*ex: 00 00 00 00 a5 LL LL LL LL*/ + /*ex: a5 LL LL LL LL 00 00 00 00*/ + /*ex: 00 00 a5 LL LL LL LL 00 00*/ + /*ex: a5 LL LL LL LL*/ + fw_data->next_index = 0; + mrvl_validate_hdr_and_len(hu, buf + i); + return; + } + + /*ex: 00 00 00 00 a5 LL LL*/ + hci_uart_recv_data(hu, buf + i, len - i); + return; + } + + for (i = 0; i < len; i++) { + fw_data->five_bytes[fw_data->next_index] = buf[i]; + if (++fw_data->next_index == 5) { + fw_data->next_index = 0; + mrvl_validate_hdr_and_len(hu, fw_data->five_bytes); + return; + } + } +} diff --git a/drivers/bluetooth/hci_uart.h b/drivers/bluetooth/hci_uart.h index 4814ff0..245cab58 100644 --- a/drivers/bluetooth/hci_uart.h +++ b/drivers/bluetooth/hci_uart.h @@ -35,7 +35,7 @@ #define HCIUARTGETFLAGS _IOR('U', 204, int) /* UART protocols */ -#define HCI_UART_MAX_PROTO 10 +#define HCI_UART_MAX_PROTO 11 #define HCI_UART_H4 0 #define HCI_UART_BCSP 1 @@ -47,6 +47,7 @@ #define HCI_UART_BCM 7 #define HCI_UART_QCA 8 #define HCI_UART_AG6XX 9 +#define HCI_UART_MRVL 10 #define HCI_UART_RAW_DEVICE 0 #define HCI_UART_RESET_ON_INIT 1 @@ -95,11 +96,16 @@ struct hci_uart { /* HCI_UART proto flag bits */ #define HCI_UART_PROTO_SET 0 #define HCI_UART_REGISTERED 1 +#define HCI_UART_DNLD_FW 2 /* TX states */ #define HCI_UART_SENDING 1 #define HCI_UART_TX_WAKEUP 2 +#ifdef CONFIG_BT_HCIUART_MRVL +void hci_uart_recv_data(struct hci_uart *hu, u8 *buf, int len); +int hci_uart_dnld_fw(struct hci_uart *hu); +#endif int hci_uart_register_proto(const struct hci_uart_proto *p); int hci_uart_unregister_proto(const struct hci_uart_proto *p); int hci_uart_tx_wakeup(struct hci_uart *hu); @@ -188,3 +194,8 @@ int qca_deinit(void); int ag6xx_init(void); int ag6xx_deinit(void); #endif + +#ifdef CONFIG_BT_HCIUART_MRVL +int mrvl_init(void); +int mrvl_deinit(void); +#endif -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html