diff options
Diffstat (limited to 'drivers/tty/ehv_bytechan.c')
| -rw-r--r-- | drivers/tty/ehv_bytechan.c | 814 |
1 files changed, 814 insertions, 0 deletions
diff --git a/drivers/tty/ehv_bytechan.c b/drivers/tty/ehv_bytechan.c new file mode 100644 index 000000000..ca5004ae3 --- /dev/null +++ b/drivers/tty/ehv_bytechan.c @@ -0,0 +1,814 @@ +// SPDX-License-Identifier: GPL-2.0 +/* ePAPR hypervisor byte channel device driver + * + * Copyright 2009-2011 Freescale Semiconductor, Inc. + * + * Author: Timur Tabi <timur@freescale.com> + * + * This driver support three distinct interfaces, all of which are related to + * ePAPR hypervisor byte channels. + * + * 1) An early-console (udbg) driver. This provides early console output + * through a byte channel. The byte channel handle must be specified in a + * Kconfig option. + * + * 2) A normal console driver. Output is sent to the byte channel designated + * for stdout in the device tree. The console driver is for handling kernel + * printk calls. + * + * 3) A tty driver, which is used to handle user-space input and output. The + * byte channel used for the console is designated as the default tty. + */ + +#include <linux/init.h> +#include <linux/slab.h> +#include <linux/err.h> +#include <linux/interrupt.h> +#include <linux/fs.h> +#include <linux/poll.h> +#include <asm/epapr_hcalls.h> +#include <linux/of.h> +#include <linux/of_irq.h> +#include <linux/platform_device.h> +#include <linux/cdev.h> +#include <linux/console.h> +#include <linux/tty.h> +#include <linux/tty_flip.h> +#include <linux/circ_buf.h> +#include <asm/udbg.h> + +/* The size of the transmit circular buffer. This must be a power of two. */ +#define BUF_SIZE 2048 + +/* Per-byte channel private data */ +struct ehv_bc_data { + struct device *dev; + struct tty_port port; + uint32_t handle; + unsigned int rx_irq; + unsigned int tx_irq; + + spinlock_t lock; /* lock for transmit buffer */ + unsigned char buf[BUF_SIZE]; /* transmit circular buffer */ + unsigned int head; /* circular buffer head */ + unsigned int tail; /* circular buffer tail */ + + int tx_irq_enabled; /* true == TX interrupt is enabled */ +}; + +/* Array of byte channel objects */ +static struct ehv_bc_data *bcs; + +/* Byte channel handle for stdout (and stdin), taken from device tree */ +static unsigned int stdout_bc; + +/* Virtual IRQ for the byte channel handle for stdin, taken from device tree */ +static unsigned int stdout_irq; + +/**************************** SUPPORT FUNCTIONS ****************************/ + +/* + * Enable the transmit interrupt + * + * Unlike a serial device, byte channels have no mechanism for disabling their + * own receive or transmit interrupts. To emulate that feature, we toggle + * the IRQ in the kernel. + * + * We cannot just blindly call enable_irq() or disable_irq(), because these + * calls are reference counted. This means that we cannot call enable_irq() + * if interrupts are already enabled. This can happen in two situations: + * + * 1. The tty layer makes two back-to-back calls to ehv_bc_tty_write() + * 2. A transmit interrupt occurs while executing ehv_bc_tx_dequeue() + * + * To work around this, we keep a flag to tell us if the IRQ is enabled or not. + */ +static void enable_tx_interrupt(struct ehv_bc_data *bc) +{ + if (!bc->tx_irq_enabled) { + enable_irq(bc->tx_irq); + bc->tx_irq_enabled = 1; + } +} + +static void disable_tx_interrupt(struct ehv_bc_data *bc) +{ + if (bc->tx_irq_enabled) { + disable_irq_nosync(bc->tx_irq); + bc->tx_irq_enabled = 0; + } +} + +/* + * find the byte channel handle to use for the console + * + * The byte channel to be used for the console is specified via a "stdout" + * property in the /chosen node. + */ +static int find_console_handle(void) +{ + struct device_node *np = of_stdout; + const uint32_t *iprop; + + /* We don't care what the aliased node is actually called. We only + * care if it's compatible with "epapr,hv-byte-channel", because that + * indicates that it's a byte channel node. + */ + if (!np || !of_device_is_compatible(np, "epapr,hv-byte-channel")) + return 0; + + stdout_irq = irq_of_parse_and_map(np, 0); + if (stdout_irq == NO_IRQ) { + pr_err("ehv-bc: no 'interrupts' property in %pOF node\n", np); + return 0; + } + + /* + * The 'hv-handle' property contains the handle for this byte channel. + */ + iprop = of_get_property(np, "hv-handle", NULL); + if (!iprop) { + pr_err("ehv-bc: no 'hv-handle' property in %s node\n", + np->name); + return 0; + } + stdout_bc = be32_to_cpu(*iprop); + return 1; +} + +static unsigned int local_ev_byte_channel_send(unsigned int handle, + unsigned int *count, + const char *p) +{ + char buffer[EV_BYTE_CHANNEL_MAX_BYTES]; + unsigned int c = *count; + + if (c < sizeof(buffer)) { + memcpy(buffer, p, c); + memset(&buffer[c], 0, sizeof(buffer) - c); + p = buffer; + } + return ev_byte_channel_send(handle, count, p); +} + +/*************************** EARLY CONSOLE DRIVER ***************************/ + +#ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC + +/* + * send a byte to a byte channel, wait if necessary + * + * This function sends a byte to a byte channel, and it waits and + * retries if the byte channel is full. It returns if the character + * has been sent, or if some error has occurred. + * + */ +static void byte_channel_spin_send(const char data) +{ + int ret, count; + + do { + count = 1; + ret = local_ev_byte_channel_send(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE, + &count, &data); + } while (ret == EV_EAGAIN); +} + +/* + * The udbg subsystem calls this function to display a single character. + * We convert CR to a CR/LF. + */ +static void ehv_bc_udbg_putc(char c) +{ + if (c == '\n') + byte_channel_spin_send('\r'); + + byte_channel_spin_send(c); +} + +/* + * early console initialization + * + * PowerPC kernels support an early printk console, also known as udbg. + * This function must be called via the ppc_md.init_early function pointer. + * At this point, the device tree has been unflattened, so we can obtain the + * byte channel handle for stdout. + * + * We only support displaying of characters (putc). We do not support + * keyboard input. + */ +void __init udbg_init_ehv_bc(void) +{ + unsigned int rx_count, tx_count; + unsigned int ret; + + /* Verify the byte channel handle */ + ret = ev_byte_channel_poll(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE, + &rx_count, &tx_count); + if (ret) + return; + + udbg_putc = ehv_bc_udbg_putc; + register_early_udbg_console(); + + udbg_printf("ehv-bc: early console using byte channel handle %u\n", + CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE); +} + +#endif + +/****************************** CONSOLE DRIVER ******************************/ + +static struct tty_driver *ehv_bc_driver; + +/* + * Byte channel console sending worker function. + * + * For consoles, if the output buffer is full, we should just spin until it + * clears. + */ +static int ehv_bc_console_byte_channel_send(unsigned int handle, const char *s, + unsigned int count) +{ + unsigned int len; + int ret = 0; + + while (count) { + len = min_t(unsigned int, count, EV_BYTE_CHANNEL_MAX_BYTES); + do { + ret = local_ev_byte_channel_send(handle, &len, s); + } while (ret == EV_EAGAIN); + count -= len; + s += len; + } + + return ret; +} + +/* + * write a string to the console + * + * This function gets called to write a string from the kernel, typically from + * a printk(). This function spins until all data is written. + * + * We copy the data to a temporary buffer because we need to insert a \r in + * front of every \n. It's more efficient to copy the data to the buffer than + * it is to make multiple hcalls for each character or each newline. + */ +static void ehv_bc_console_write(struct console *co, const char *s, + unsigned int count) +{ + char s2[EV_BYTE_CHANNEL_MAX_BYTES]; + unsigned int i, j = 0; + char c; + + for (i = 0; i < count; i++) { + c = *s++; + + if (c == '\n') + s2[j++] = '\r'; + + s2[j++] = c; + if (j >= (EV_BYTE_CHANNEL_MAX_BYTES - 1)) { + if (ehv_bc_console_byte_channel_send(stdout_bc, s2, j)) + return; + j = 0; + } + } + + if (j) + ehv_bc_console_byte_channel_send(stdout_bc, s2, j); +} + +/* + * When /dev/console is opened, the kernel iterates the console list looking + * for one with ->device and then calls that method. On success, it expects + * the passed-in int* to contain the minor number to use. + */ +static struct tty_driver *ehv_bc_console_device(struct console *co, int *index) +{ + *index = co->index; + + return ehv_bc_driver; +} + +static struct console ehv_bc_console = { + .name = "ttyEHV", + .write = ehv_bc_console_write, + .device = ehv_bc_console_device, + .flags = CON_PRINTBUFFER | CON_ENABLED, +}; + +/* + * Console initialization + * + * This is the first function that is called after the device tree is + * available, so here is where we determine the byte channel handle and IRQ for + * stdout/stdin, even though that information is used by the tty and character + * drivers. + */ +static int __init ehv_bc_console_init(void) +{ + if (!find_console_handle()) { + pr_debug("ehv-bc: stdout is not a byte channel\n"); + return -ENODEV; + } + +#ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC + /* Print a friendly warning if the user chose the wrong byte channel + * handle for udbg. + */ + if (stdout_bc != CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE) + pr_warn("ehv-bc: udbg handle %u is not the stdout handle\n", + CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE); +#endif + + /* add_preferred_console() must be called before register_console(), + otherwise it won't work. However, we don't want to enumerate all the + byte channels here, either, since we only care about one. */ + + add_preferred_console(ehv_bc_console.name, ehv_bc_console.index, NULL); + register_console(&ehv_bc_console); + + pr_info("ehv-bc: registered console driver for byte channel %u\n", + stdout_bc); + + return 0; +} +console_initcall(ehv_bc_console_init); + +/******************************** TTY DRIVER ********************************/ + +/* + * byte channel receive interrupt handler + * + * This ISR is called whenever data is available on a byte channel. + */ +static irqreturn_t ehv_bc_tty_rx_isr(int irq, void *data) +{ + struct ehv_bc_data *bc = data; + unsigned int rx_count, tx_count, len; + int count; + char buffer[EV_BYTE_CHANNEL_MAX_BYTES]; + int ret; + + /* Find out how much data needs to be read, and then ask the TTY layer + * if it can handle that much. We want to ensure that every byte we + * read from the byte channel will be accepted by the TTY layer. + */ + ev_byte_channel_poll(bc->handle, &rx_count, &tx_count); + count = tty_buffer_request_room(&bc->port, rx_count); + + /* 'count' is the maximum amount of data the TTY layer can accept at + * this time. However, during testing, I was never able to get 'count' + * to be less than 'rx_count'. I'm not sure whether I'm calling it + * correctly. + */ + + while (count > 0) { + len = min_t(unsigned int, count, sizeof(buffer)); + + /* Read some data from the byte channel. This function will + * never return more than EV_BYTE_CHANNEL_MAX_BYTES bytes. + */ + ev_byte_channel_receive(bc->handle, &len, buffer); + + /* 'len' is now the amount of data that's been received. 'len' + * can't be zero, and most likely it's equal to one. + */ + + /* Pass the received data to the tty layer. */ + ret = tty_insert_flip_string(&bc->port, buffer, len); + + /* 'ret' is the number of bytes that the TTY layer accepted. + * If it's not equal to 'len', then it means the buffer is + * full, which should never happen. If it does happen, we can + * exit gracefully, but we drop the last 'len - ret' characters + * that we read from the byte channel. + */ + if (ret != len) + break; + + count -= len; + } + + /* Tell the tty layer that we're done. */ + tty_flip_buffer_push(&bc->port); + + return IRQ_HANDLED; +} + +/* + * dequeue the transmit buffer to the hypervisor + * + * This function, which can be called in interrupt context, dequeues as much + * data as possible from the transmit buffer to the byte channel. + */ +static void ehv_bc_tx_dequeue(struct ehv_bc_data *bc) +{ + unsigned int count; + unsigned int len, ret; + unsigned long flags; + + do { + spin_lock_irqsave(&bc->lock, flags); + len = min_t(unsigned int, + CIRC_CNT_TO_END(bc->head, bc->tail, BUF_SIZE), + EV_BYTE_CHANNEL_MAX_BYTES); + + ret = local_ev_byte_channel_send(bc->handle, &len, bc->buf + bc->tail); + + /* 'len' is valid only if the return code is 0 or EV_EAGAIN */ + if (!ret || (ret == EV_EAGAIN)) + bc->tail = (bc->tail + len) & (BUF_SIZE - 1); + + count = CIRC_CNT(bc->head, bc->tail, BUF_SIZE); + spin_unlock_irqrestore(&bc->lock, flags); + } while (count && !ret); + + spin_lock_irqsave(&bc->lock, flags); + if (CIRC_CNT(bc->head, bc->tail, BUF_SIZE)) + /* + * If we haven't emptied the buffer, then enable the TX IRQ. + * We'll get an interrupt when there's more room in the + * hypervisor's output buffer. + */ + enable_tx_interrupt(bc); + else + disable_tx_interrupt(bc); + spin_unlock_irqrestore(&bc->lock, flags); +} + +/* + * byte channel transmit interrupt handler + * + * This ISR is called whenever space becomes available for transmitting + * characters on a byte channel. + */ +static irqreturn_t ehv_bc_tty_tx_isr(int irq, void *data) +{ + struct ehv_bc_data *bc = data; + + ehv_bc_tx_dequeue(bc); + tty_port_tty_wakeup(&bc->port); + + return IRQ_HANDLED; +} + +/* + * This function is called when the tty layer has data for us send. We store + * the data first in a circular buffer, and then dequeue as much of that data + * as possible. + * + * We don't need to worry about whether there is enough room in the buffer for + * all the data. The purpose of ehv_bc_tty_write_room() is to tell the tty + * layer how much data it can safely send to us. We guarantee that + * ehv_bc_tty_write_room() will never lie, so the tty layer will never send us + * too much data. + */ +static int ehv_bc_tty_write(struct tty_struct *ttys, const unsigned char *s, + int count) +{ + struct ehv_bc_data *bc = ttys->driver_data; + unsigned long flags; + unsigned int len; + unsigned int written = 0; + + while (1) { + spin_lock_irqsave(&bc->lock, flags); + len = CIRC_SPACE_TO_END(bc->head, bc->tail, BUF_SIZE); + if (count < len) + len = count; + if (len) { + memcpy(bc->buf + bc->head, s, len); + bc->head = (bc->head + len) & (BUF_SIZE - 1); + } + spin_unlock_irqrestore(&bc->lock, flags); + if (!len) + break; + + s += len; + count -= len; + written += len; + } + + ehv_bc_tx_dequeue(bc); + + return written; +} + +/* + * This function can be called multiple times for a given tty_struct, which is + * why we initialize bc->ttys in ehv_bc_tty_port_activate() instead. + * + * The tty layer will still call this function even if the device was not + * registered (i.e. tty_register_device() was not called). This happens + * because tty_register_device() is optional and some legacy drivers don't + * use it. So we need to check for that. + */ +static int ehv_bc_tty_open(struct tty_struct *ttys, struct file *filp) +{ + struct ehv_bc_data *bc = &bcs[ttys->index]; + + if (!bc->dev) + return -ENODEV; + + return tty_port_open(&bc->port, ttys, filp); +} + +/* + * Amazingly, if ehv_bc_tty_open() returns an error code, the tty layer will + * still call this function to close the tty device. So we can't assume that + * the tty port has been initialized. + */ +static void ehv_bc_tty_close(struct tty_struct *ttys, struct file *filp) +{ + struct ehv_bc_data *bc = &bcs[ttys->index]; + + if (bc->dev) + tty_port_close(&bc->port, ttys, filp); +} + +/* + * Return the amount of space in the output buffer + * + * This is actually a contract between the driver and the tty layer outlining + * how much write room the driver can guarantee will be sent OR BUFFERED. This + * driver MUST honor the return value. + */ +static int ehv_bc_tty_write_room(struct tty_struct *ttys) +{ + struct ehv_bc_data *bc = ttys->driver_data; + unsigned long flags; + int count; + + spin_lock_irqsave(&bc->lock, flags); + count = CIRC_SPACE(bc->head, bc->tail, BUF_SIZE); + spin_unlock_irqrestore(&bc->lock, flags); + + return count; +} + +/* + * Stop sending data to the tty layer + * + * This function is called when the tty layer's input buffers are getting full, + * so the driver should stop sending it data. The easiest way to do this is to + * disable the RX IRQ, which will prevent ehv_bc_tty_rx_isr() from being + * called. + * + * The hypervisor will continue to queue up any incoming data. If there is any + * data in the queue when the RX interrupt is enabled, we'll immediately get an + * RX interrupt. + */ +static void ehv_bc_tty_throttle(struct tty_struct *ttys) +{ + struct ehv_bc_data *bc = ttys->driver_data; + + disable_irq(bc->rx_irq); +} + +/* + * Resume sending data to the tty layer + * + * This function is called after previously calling ehv_bc_tty_throttle(). The + * tty layer's input buffers now have more room, so the driver can resume + * sending it data. + */ +static void ehv_bc_tty_unthrottle(struct tty_struct *ttys) +{ + struct ehv_bc_data *bc = ttys->driver_data; + + /* If there is any data in the queue when the RX interrupt is enabled, + * we'll immediately get an RX interrupt. + */ + enable_irq(bc->rx_irq); +} + +static void ehv_bc_tty_hangup(struct tty_struct *ttys) +{ + struct ehv_bc_data *bc = ttys->driver_data; + + ehv_bc_tx_dequeue(bc); + tty_port_hangup(&bc->port); +} + +/* + * TTY driver operations + * + * If we could ask the hypervisor how much data is still in the TX buffer, or + * at least how big the TX buffers are, then we could implement the + * .wait_until_sent and .chars_in_buffer functions. + */ +static const struct tty_operations ehv_bc_ops = { + .open = ehv_bc_tty_open, + .close = ehv_bc_tty_close, + .write = ehv_bc_tty_write, + .write_room = ehv_bc_tty_write_room, + .throttle = ehv_bc_tty_throttle, + .unthrottle = ehv_bc_tty_unthrottle, + .hangup = ehv_bc_tty_hangup, +}; + +/* + * initialize the TTY port + * + * This function will only be called once, no matter how many times + * ehv_bc_tty_open() is called. That's why we register the ISR here, and also + * why we initialize tty_struct-related variables here. + */ +static int ehv_bc_tty_port_activate(struct tty_port *port, + struct tty_struct *ttys) +{ + struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port); + int ret; + + ttys->driver_data = bc; + + ret = request_irq(bc->rx_irq, ehv_bc_tty_rx_isr, 0, "ehv-bc", bc); + if (ret < 0) { + dev_err(bc->dev, "could not request rx irq %u (ret=%i)\n", + bc->rx_irq, ret); + return ret; + } + + /* request_irq also enables the IRQ */ + bc->tx_irq_enabled = 1; + + ret = request_irq(bc->tx_irq, ehv_bc_tty_tx_isr, 0, "ehv-bc", bc); + if (ret < 0) { + dev_err(bc->dev, "could not request tx irq %u (ret=%i)\n", + bc->tx_irq, ret); + free_irq(bc->rx_irq, bc); + return ret; + } + + /* The TX IRQ is enabled only when we can't write all the data to the + * byte channel at once, so by default it's disabled. + */ + disable_tx_interrupt(bc); + + return 0; +} + +static void ehv_bc_tty_port_shutdown(struct tty_port *port) +{ + struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port); + + free_irq(bc->tx_irq, bc); + free_irq(bc->rx_irq, bc); +} + +static const struct tty_port_operations ehv_bc_tty_port_ops = { + .activate = ehv_bc_tty_port_activate, + .shutdown = ehv_bc_tty_port_shutdown, +}; + +static int ehv_bc_tty_probe(struct platform_device *pdev) +{ + struct device_node *np = pdev->dev.of_node; + struct ehv_bc_data *bc; + const uint32_t *iprop; + unsigned int handle; + int ret; + static unsigned int index = 1; + unsigned int i; + + iprop = of_get_property(np, "hv-handle", NULL); + if (!iprop) { + dev_err(&pdev->dev, "no 'hv-handle' property in %s node\n", + np->name); + return -ENODEV; + } + + /* We already told the console layer that the index for the console + * device is zero, so we need to make sure that we use that index when + * we probe the console byte channel node. + */ + handle = be32_to_cpu(*iprop); + i = (handle == stdout_bc) ? 0 : index++; + bc = &bcs[i]; + + bc->handle = handle; + bc->head = 0; + bc->tail = 0; + spin_lock_init(&bc->lock); + + bc->rx_irq = irq_of_parse_and_map(np, 0); + bc->tx_irq = irq_of_parse_and_map(np, 1); + if ((bc->rx_irq == NO_IRQ) || (bc->tx_irq == NO_IRQ)) { + dev_err(&pdev->dev, "no 'interrupts' property in %s node\n", + np->name); + ret = -ENODEV; + goto error; + } + + tty_port_init(&bc->port); + bc->port.ops = &ehv_bc_tty_port_ops; + + bc->dev = tty_port_register_device(&bc->port, ehv_bc_driver, i, + &pdev->dev); + if (IS_ERR(bc->dev)) { + ret = PTR_ERR(bc->dev); + dev_err(&pdev->dev, "could not register tty (ret=%i)\n", ret); + goto error; + } + + dev_set_drvdata(&pdev->dev, bc); + + dev_info(&pdev->dev, "registered /dev/%s%u for byte channel %u\n", + ehv_bc_driver->name, i, bc->handle); + + return 0; + +error: + tty_port_destroy(&bc->port); + irq_dispose_mapping(bc->tx_irq); + irq_dispose_mapping(bc->rx_irq); + + memset(bc, 0, sizeof(struct ehv_bc_data)); + return ret; +} + +static const struct of_device_id ehv_bc_tty_of_ids[] = { + { .compatible = "epapr,hv-byte-channel" }, + {} +}; + +static struct platform_driver ehv_bc_tty_driver = { + .driver = { + .name = "ehv-bc", + .of_match_table = ehv_bc_tty_of_ids, + .suppress_bind_attrs = true, + }, + .probe = ehv_bc_tty_probe, +}; + +/** + * ehv_bc_init - ePAPR hypervisor byte channel driver initialization + * + * This function is called when this driver is loaded. + */ +static int __init ehv_bc_init(void) +{ + struct device_node *np; + unsigned int count = 0; /* Number of elements in bcs[] */ + int ret; + + pr_info("ePAPR hypervisor byte channel driver\n"); + + /* Count the number of byte channels */ + for_each_compatible_node(np, NULL, "epapr,hv-byte-channel") + count++; + + if (!count) + return -ENODEV; + + /* The array index of an element in bcs[] is the same as the tty index + * for that element. If you know the address of an element in the + * array, then you can use pointer math (e.g. "bc - bcs") to get its + * tty index. + */ + bcs = kcalloc(count, sizeof(struct ehv_bc_data), GFP_KERNEL); + if (!bcs) + return -ENOMEM; + + ehv_bc_driver = alloc_tty_driver(count); + if (!ehv_bc_driver) { + ret = -ENOMEM; + goto err_free_bcs; + } + + ehv_bc_driver->driver_name = "ehv-bc"; + ehv_bc_driver->name = ehv_bc_console.name; + ehv_bc_driver->type = TTY_DRIVER_TYPE_CONSOLE; + ehv_bc_driver->subtype = SYSTEM_TYPE_CONSOLE; + ehv_bc_driver->init_termios = tty_std_termios; + ehv_bc_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV; + tty_set_operations(ehv_bc_driver, &ehv_bc_ops); + + ret = tty_register_driver(ehv_bc_driver); + if (ret) { + pr_err("ehv-bc: could not register tty driver (ret=%i)\n", ret); + goto err_put_tty_driver; + } + + ret = platform_driver_register(&ehv_bc_tty_driver); + if (ret) { + pr_err("ehv-bc: could not register platform driver (ret=%i)\n", + ret); + goto err_deregister_tty_driver; + } + + return 0; + +err_deregister_tty_driver: + tty_unregister_driver(ehv_bc_driver); +err_put_tty_driver: + put_tty_driver(ehv_bc_driver); +err_free_bcs: + kfree(bcs); + + return ret; +} +device_initcall(ehv_bc_init); |