Root/drivers/tty/ehv_bytechan.c

1/* ePAPR hypervisor byte channel device driver
2 *
3 * Copyright 2009-2011 Freescale Semiconductor, Inc.
4 *
5 * Author: Timur Tabi <timur@freescale.com>
6 *
7 * This file is licensed under the terms of the GNU General Public License
8 * version 2. This program is licensed "as is" without any warranty of any
9 * kind, whether express or implied.
10 *
11 * This driver support three distinct interfaces, all of which are related to
12 * ePAPR hypervisor byte channels.
13 *
14 * 1) An early-console (udbg) driver. This provides early console output
15 * through a byte channel. The byte channel handle must be specified in a
16 * Kconfig option.
17 *
18 * 2) A normal console driver. Output is sent to the byte channel designated
19 * for stdout in the device tree. The console driver is for handling kernel
20 * printk calls.
21 *
22 * 3) A tty driver, which is used to handle user-space input and output. The
23 * byte channel used for the console is designated as the default tty.
24 */
25
26#include <linux/module.h>
27#include <linux/init.h>
28#include <linux/slab.h>
29#include <linux/err.h>
30#include <linux/interrupt.h>
31#include <linux/fs.h>
32#include <linux/poll.h>
33#include <asm/epapr_hcalls.h>
34#include <linux/of.h>
35#include <linux/platform_device.h>
36#include <linux/cdev.h>
37#include <linux/console.h>
38#include <linux/tty.h>
39#include <linux/tty_flip.h>
40#include <linux/circ_buf.h>
41#include <asm/udbg.h>
42
43/* The size of the transmit circular buffer. This must be a power of two. */
44#define BUF_SIZE 2048
45
46/* Per-byte channel private data */
47struct ehv_bc_data {
48    struct device *dev;
49    struct tty_port port;
50    uint32_t handle;
51    unsigned int rx_irq;
52    unsigned int tx_irq;
53
54    spinlock_t lock; /* lock for transmit buffer */
55    unsigned char buf[BUF_SIZE]; /* transmit circular buffer */
56    unsigned int head; /* circular buffer head */
57    unsigned int tail; /* circular buffer tail */
58
59    int tx_irq_enabled; /* true == TX interrupt is enabled */
60};
61
62/* Array of byte channel objects */
63static struct ehv_bc_data *bcs;
64
65/* Byte channel handle for stdout (and stdin), taken from device tree */
66static unsigned int stdout_bc;
67
68/* Virtual IRQ for the byte channel handle for stdin, taken from device tree */
69static unsigned int stdout_irq;
70
71/**************************** SUPPORT FUNCTIONS ****************************/
72
73/*
74 * Enable the transmit interrupt
75 *
76 * Unlike a serial device, byte channels have no mechanism for disabling their
77 * own receive or transmit interrupts. To emulate that feature, we toggle
78 * the IRQ in the kernel.
79 *
80 * We cannot just blindly call enable_irq() or disable_irq(), because these
81 * calls are reference counted. This means that we cannot call enable_irq()
82 * if interrupts are already enabled. This can happen in two situations:
83 *
84 * 1. The tty layer makes two back-to-back calls to ehv_bc_tty_write()
85 * 2. A transmit interrupt occurs while executing ehv_bc_tx_dequeue()
86 *
87 * To work around this, we keep a flag to tell us if the IRQ is enabled or not.
88 */
89static void enable_tx_interrupt(struct ehv_bc_data *bc)
90{
91    if (!bc->tx_irq_enabled) {
92        enable_irq(bc->tx_irq);
93        bc->tx_irq_enabled = 1;
94    }
95}
96
97static void disable_tx_interrupt(struct ehv_bc_data *bc)
98{
99    if (bc->tx_irq_enabled) {
100        disable_irq_nosync(bc->tx_irq);
101        bc->tx_irq_enabled = 0;
102    }
103}
104
105/*
106 * find the byte channel handle to use for the console
107 *
108 * The byte channel to be used for the console is specified via a "stdout"
109 * property in the /chosen node.
110 *
111 * For compatible with legacy device trees, we also look for a "stdout" alias.
112 */
113static int find_console_handle(void)
114{
115    struct device_node *np, *np2;
116    const char *sprop = NULL;
117    const uint32_t *iprop;
118
119    np = of_find_node_by_path("/chosen");
120    if (np)
121        sprop = of_get_property(np, "stdout-path", NULL);
122
123    if (!np || !sprop) {
124        of_node_put(np);
125        np = of_find_node_by_name(NULL, "aliases");
126        if (np)
127            sprop = of_get_property(np, "stdout", NULL);
128    }
129
130    if (!sprop) {
131        of_node_put(np);
132        return 0;
133    }
134
135    /* We don't care what the aliased node is actually called. We only
136     * care if it's compatible with "epapr,hv-byte-channel", because that
137     * indicates that it's a byte channel node. We use a temporary
138     * variable, 'np2', because we can't release 'np' until we're done with
139     * 'sprop'.
140     */
141    np2 = of_find_node_by_path(sprop);
142    of_node_put(np);
143    np = np2;
144    if (!np) {
145        pr_warning("ehv-bc: stdout node '%s' does not exist\n", sprop);
146        return 0;
147    }
148
149    /* Is it a byte channel? */
150    if (!of_device_is_compatible(np, "epapr,hv-byte-channel")) {
151        of_node_put(np);
152        return 0;
153    }
154
155    stdout_irq = irq_of_parse_and_map(np, 0);
156    if (stdout_irq == NO_IRQ) {
157        pr_err("ehv-bc: no 'interrupts' property in %s node\n", sprop);
158        of_node_put(np);
159        return 0;
160    }
161
162    /*
163     * The 'hv-handle' property contains the handle for this byte channel.
164     */
165    iprop = of_get_property(np, "hv-handle", NULL);
166    if (!iprop) {
167        pr_err("ehv-bc: no 'hv-handle' property in %s node\n",
168               np->name);
169        of_node_put(np);
170        return 0;
171    }
172    stdout_bc = be32_to_cpu(*iprop);
173
174    of_node_put(np);
175    return 1;
176}
177
178/*************************** EARLY CONSOLE DRIVER ***************************/
179
180#ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC
181
182/*
183 * send a byte to a byte channel, wait if necessary
184 *
185 * This function sends a byte to a byte channel, and it waits and
186 * retries if the byte channel is full. It returns if the character
187 * has been sent, or if some error has occurred.
188 *
189 */
190static void byte_channel_spin_send(const char data)
191{
192    int ret, count;
193
194    do {
195        count = 1;
196        ret = ev_byte_channel_send(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE,
197                       &count, &data);
198    } while (ret == EV_EAGAIN);
199}
200
201/*
202 * The udbg subsystem calls this function to display a single character.
203 * We convert CR to a CR/LF.
204 */
205static void ehv_bc_udbg_putc(char c)
206{
207    if (c == '\n')
208        byte_channel_spin_send('\r');
209
210    byte_channel_spin_send(c);
211}
212
213/*
214 * early console initialization
215 *
216 * PowerPC kernels support an early printk console, also known as udbg.
217 * This function must be called via the ppc_md.init_early function pointer.
218 * At this point, the device tree has been unflattened, so we can obtain the
219 * byte channel handle for stdout.
220 *
221 * We only support displaying of characters (putc). We do not support
222 * keyboard input.
223 */
224void __init udbg_init_ehv_bc(void)
225{
226    unsigned int rx_count, tx_count;
227    unsigned int ret;
228
229    /* Verify the byte channel handle */
230    ret = ev_byte_channel_poll(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE,
231                   &rx_count, &tx_count);
232    if (ret)
233        return;
234
235    udbg_putc = ehv_bc_udbg_putc;
236    register_early_udbg_console();
237
238    udbg_printf("ehv-bc: early console using byte channel handle %u\n",
239            CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE);
240}
241
242#endif
243
244/****************************** CONSOLE DRIVER ******************************/
245
246static struct tty_driver *ehv_bc_driver;
247
248/*
249 * Byte channel console sending worker function.
250 *
251 * For consoles, if the output buffer is full, we should just spin until it
252 * clears.
253 */
254static int ehv_bc_console_byte_channel_send(unsigned int handle, const char *s,
255                 unsigned int count)
256{
257    unsigned int len;
258    int ret = 0;
259
260    while (count) {
261        len = min_t(unsigned int, count, EV_BYTE_CHANNEL_MAX_BYTES);
262        do {
263            ret = ev_byte_channel_send(handle, &len, s);
264        } while (ret == EV_EAGAIN);
265        count -= len;
266        s += len;
267    }
268
269    return ret;
270}
271
272/*
273 * write a string to the console
274 *
275 * This function gets called to write a string from the kernel, typically from
276 * a printk(). This function spins until all data is written.
277 *
278 * We copy the data to a temporary buffer because we need to insert a \r in
279 * front of every \n. It's more efficient to copy the data to the buffer than
280 * it is to make multiple hcalls for each character or each newline.
281 */
282static void ehv_bc_console_write(struct console *co, const char *s,
283                 unsigned int count)
284{
285    char s2[EV_BYTE_CHANNEL_MAX_BYTES];
286    unsigned int i, j = 0;
287    char c;
288
289    for (i = 0; i < count; i++) {
290        c = *s++;
291
292        if (c == '\n')
293            s2[j++] = '\r';
294
295        s2[j++] = c;
296        if (j >= (EV_BYTE_CHANNEL_MAX_BYTES - 1)) {
297            if (ehv_bc_console_byte_channel_send(stdout_bc, s2, j))
298                return;
299            j = 0;
300        }
301    }
302
303    if (j)
304        ehv_bc_console_byte_channel_send(stdout_bc, s2, j);
305}
306
307/*
308 * When /dev/console is opened, the kernel iterates the console list looking
309 * for one with ->device and then calls that method. On success, it expects
310 * the passed-in int* to contain the minor number to use.
311 */
312static struct tty_driver *ehv_bc_console_device(struct console *co, int *index)
313{
314    *index = co->index;
315
316    return ehv_bc_driver;
317}
318
319static struct console ehv_bc_console = {
320    .name = "ttyEHV",
321    .write = ehv_bc_console_write,
322    .device = ehv_bc_console_device,
323    .flags = CON_PRINTBUFFER | CON_ENABLED,
324};
325
326/*
327 * Console initialization
328 *
329 * This is the first function that is called after the device tree is
330 * available, so here is where we determine the byte channel handle and IRQ for
331 * stdout/stdin, even though that information is used by the tty and character
332 * drivers.
333 */
334static int __init ehv_bc_console_init(void)
335{
336    if (!find_console_handle()) {
337        pr_debug("ehv-bc: stdout is not a byte channel\n");
338        return -ENODEV;
339    }
340
341#ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC
342    /* Print a friendly warning if the user chose the wrong byte channel
343     * handle for udbg.
344     */
345    if (stdout_bc != CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE)
346        pr_warning("ehv-bc: udbg handle %u is not the stdout handle\n",
347               CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE);
348#endif
349
350    /* add_preferred_console() must be called before register_console(),
351       otherwise it won't work. However, we don't want to enumerate all the
352       byte channels here, either, since we only care about one. */
353
354    add_preferred_console(ehv_bc_console.name, ehv_bc_console.index, NULL);
355    register_console(&ehv_bc_console);
356
357    pr_info("ehv-bc: registered console driver for byte channel %u\n",
358        stdout_bc);
359
360    return 0;
361}
362console_initcall(ehv_bc_console_init);
363
364/******************************** TTY DRIVER ********************************/
365
366/*
367 * byte channel receive interupt handler
368 *
369 * This ISR is called whenever data is available on a byte channel.
370 */
371static irqreturn_t ehv_bc_tty_rx_isr(int irq, void *data)
372{
373    struct ehv_bc_data *bc = data;
374    unsigned int rx_count, tx_count, len;
375    int count;
376    char buffer[EV_BYTE_CHANNEL_MAX_BYTES];
377    int ret;
378
379    /* Find out how much data needs to be read, and then ask the TTY layer
380     * if it can handle that much. We want to ensure that every byte we
381     * read from the byte channel will be accepted by the TTY layer.
382     */
383    ev_byte_channel_poll(bc->handle, &rx_count, &tx_count);
384    count = tty_buffer_request_room(&bc->port, rx_count);
385
386    /* 'count' is the maximum amount of data the TTY layer can accept at
387     * this time. However, during testing, I was never able to get 'count'
388     * to be less than 'rx_count'. I'm not sure whether I'm calling it
389     * correctly.
390     */
391
392    while (count > 0) {
393        len = min_t(unsigned int, count, sizeof(buffer));
394
395        /* Read some data from the byte channel. This function will
396         * never return more than EV_BYTE_CHANNEL_MAX_BYTES bytes.
397         */
398        ev_byte_channel_receive(bc->handle, &len, buffer);
399
400        /* 'len' is now the amount of data that's been received. 'len'
401         * can't be zero, and most likely it's equal to one.
402         */
403
404        /* Pass the received data to the tty layer. */
405        ret = tty_insert_flip_string(&bc->port, buffer, len);
406
407        /* 'ret' is the number of bytes that the TTY layer accepted.
408         * If it's not equal to 'len', then it means the buffer is
409         * full, which should never happen. If it does happen, we can
410         * exit gracefully, but we drop the last 'len - ret' characters
411         * that we read from the byte channel.
412         */
413        if (ret != len)
414            break;
415
416        count -= len;
417    }
418
419    /* Tell the tty layer that we're done. */
420    tty_flip_buffer_push(&bc->port);
421
422    return IRQ_HANDLED;
423}
424
425/*
426 * dequeue the transmit buffer to the hypervisor
427 *
428 * This function, which can be called in interrupt context, dequeues as much
429 * data as possible from the transmit buffer to the byte channel.
430 */
431static void ehv_bc_tx_dequeue(struct ehv_bc_data *bc)
432{
433    unsigned int count;
434    unsigned int len, ret;
435    unsigned long flags;
436
437    do {
438        spin_lock_irqsave(&bc->lock, flags);
439        len = min_t(unsigned int,
440                CIRC_CNT_TO_END(bc->head, bc->tail, BUF_SIZE),
441                EV_BYTE_CHANNEL_MAX_BYTES);
442
443        ret = ev_byte_channel_send(bc->handle, &len, bc->buf + bc->tail);
444
445        /* 'len' is valid only if the return code is 0 or EV_EAGAIN */
446        if (!ret || (ret == EV_EAGAIN))
447            bc->tail = (bc->tail + len) & (BUF_SIZE - 1);
448
449        count = CIRC_CNT(bc->head, bc->tail, BUF_SIZE);
450        spin_unlock_irqrestore(&bc->lock, flags);
451    } while (count && !ret);
452
453    spin_lock_irqsave(&bc->lock, flags);
454    if (CIRC_CNT(bc->head, bc->tail, BUF_SIZE))
455        /*
456         * If we haven't emptied the buffer, then enable the TX IRQ.
457         * We'll get an interrupt when there's more room in the
458         * hypervisor's output buffer.
459         */
460        enable_tx_interrupt(bc);
461    else
462        disable_tx_interrupt(bc);
463    spin_unlock_irqrestore(&bc->lock, flags);
464}
465
466/*
467 * byte channel transmit interupt handler
468 *
469 * This ISR is called whenever space becomes available for transmitting
470 * characters on a byte channel.
471 */
472static irqreturn_t ehv_bc_tty_tx_isr(int irq, void *data)
473{
474    struct ehv_bc_data *bc = data;
475    struct tty_struct *ttys = tty_port_tty_get(&bc->port);
476
477    ehv_bc_tx_dequeue(bc);
478    if (ttys) {
479        tty_wakeup(ttys);
480        tty_kref_put(ttys);
481    }
482
483    return IRQ_HANDLED;
484}
485
486/*
487 * This function is called when the tty layer has data for us send. We store
488 * the data first in a circular buffer, and then dequeue as much of that data
489 * as possible.
490 *
491 * We don't need to worry about whether there is enough room in the buffer for
492 * all the data. The purpose of ehv_bc_tty_write_room() is to tell the tty
493 * layer how much data it can safely send to us. We guarantee that
494 * ehv_bc_tty_write_room() will never lie, so the tty layer will never send us
495 * too much data.
496 */
497static int ehv_bc_tty_write(struct tty_struct *ttys, const unsigned char *s,
498                int count)
499{
500    struct ehv_bc_data *bc = ttys->driver_data;
501    unsigned long flags;
502    unsigned int len;
503    unsigned int written = 0;
504
505    while (1) {
506        spin_lock_irqsave(&bc->lock, flags);
507        len = CIRC_SPACE_TO_END(bc->head, bc->tail, BUF_SIZE);
508        if (count < len)
509            len = count;
510        if (len) {
511            memcpy(bc->buf + bc->head, s, len);
512            bc->head = (bc->head + len) & (BUF_SIZE - 1);
513        }
514        spin_unlock_irqrestore(&bc->lock, flags);
515        if (!len)
516            break;
517
518        s += len;
519        count -= len;
520        written += len;
521    }
522
523    ehv_bc_tx_dequeue(bc);
524
525    return written;
526}
527
528/*
529 * This function can be called multiple times for a given tty_struct, which is
530 * why we initialize bc->ttys in ehv_bc_tty_port_activate() instead.
531 *
532 * The tty layer will still call this function even if the device was not
533 * registered (i.e. tty_register_device() was not called). This happens
534 * because tty_register_device() is optional and some legacy drivers don't
535 * use it. So we need to check for that.
536 */
537static int ehv_bc_tty_open(struct tty_struct *ttys, struct file *filp)
538{
539    struct ehv_bc_data *bc = &bcs[ttys->index];
540
541    if (!bc->dev)
542        return -ENODEV;
543
544    return tty_port_open(&bc->port, ttys, filp);
545}
546
547/*
548 * Amazingly, if ehv_bc_tty_open() returns an error code, the tty layer will
549 * still call this function to close the tty device. So we can't assume that
550 * the tty port has been initialized.
551 */
552static void ehv_bc_tty_close(struct tty_struct *ttys, struct file *filp)
553{
554    struct ehv_bc_data *bc = &bcs[ttys->index];
555
556    if (bc->dev)
557        tty_port_close(&bc->port, ttys, filp);
558}
559
560/*
561 * Return the amount of space in the output buffer
562 *
563 * This is actually a contract between the driver and the tty layer outlining
564 * how much write room the driver can guarantee will be sent OR BUFFERED. This
565 * driver MUST honor the return value.
566 */
567static int ehv_bc_tty_write_room(struct tty_struct *ttys)
568{
569    struct ehv_bc_data *bc = ttys->driver_data;
570    unsigned long flags;
571    int count;
572
573    spin_lock_irqsave(&bc->lock, flags);
574    count = CIRC_SPACE(bc->head, bc->tail, BUF_SIZE);
575    spin_unlock_irqrestore(&bc->lock, flags);
576
577    return count;
578}
579
580/*
581 * Stop sending data to the tty layer
582 *
583 * This function is called when the tty layer's input buffers are getting full,
584 * so the driver should stop sending it data. The easiest way to do this is to
585 * disable the RX IRQ, which will prevent ehv_bc_tty_rx_isr() from being
586 * called.
587 *
588 * The hypervisor will continue to queue up any incoming data. If there is any
589 * data in the queue when the RX interrupt is enabled, we'll immediately get an
590 * RX interrupt.
591 */
592static void ehv_bc_tty_throttle(struct tty_struct *ttys)
593{
594    struct ehv_bc_data *bc = ttys->driver_data;
595
596    disable_irq(bc->rx_irq);
597}
598
599/*
600 * Resume sending data to the tty layer
601 *
602 * This function is called after previously calling ehv_bc_tty_throttle(). The
603 * tty layer's input buffers now have more room, so the driver can resume
604 * sending it data.
605 */
606static void ehv_bc_tty_unthrottle(struct tty_struct *ttys)
607{
608    struct ehv_bc_data *bc = ttys->driver_data;
609
610    /* If there is any data in the queue when the RX interrupt is enabled,
611     * we'll immediately get an RX interrupt.
612     */
613    enable_irq(bc->rx_irq);
614}
615
616static void ehv_bc_tty_hangup(struct tty_struct *ttys)
617{
618    struct ehv_bc_data *bc = ttys->driver_data;
619
620    ehv_bc_tx_dequeue(bc);
621    tty_port_hangup(&bc->port);
622}
623
624/*
625 * TTY driver operations
626 *
627 * If we could ask the hypervisor how much data is still in the TX buffer, or
628 * at least how big the TX buffers are, then we could implement the
629 * .wait_until_sent and .chars_in_buffer functions.
630 */
631static const struct tty_operations ehv_bc_ops = {
632    .open = ehv_bc_tty_open,
633    .close = ehv_bc_tty_close,
634    .write = ehv_bc_tty_write,
635    .write_room = ehv_bc_tty_write_room,
636    .throttle = ehv_bc_tty_throttle,
637    .unthrottle = ehv_bc_tty_unthrottle,
638    .hangup = ehv_bc_tty_hangup,
639};
640
641/*
642 * initialize the TTY port
643 *
644 * This function will only be called once, no matter how many times
645 * ehv_bc_tty_open() is called. That's why we register the ISR here, and also
646 * why we initialize tty_struct-related variables here.
647 */
648static int ehv_bc_tty_port_activate(struct tty_port *port,
649                    struct tty_struct *ttys)
650{
651    struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port);
652    int ret;
653
654    ttys->driver_data = bc;
655
656    ret = request_irq(bc->rx_irq, ehv_bc_tty_rx_isr, 0, "ehv-bc", bc);
657    if (ret < 0) {
658        dev_err(bc->dev, "could not request rx irq %u (ret=%i)\n",
659               bc->rx_irq, ret);
660        return ret;
661    }
662
663    /* request_irq also enables the IRQ */
664    bc->tx_irq_enabled = 1;
665
666    ret = request_irq(bc->tx_irq, ehv_bc_tty_tx_isr, 0, "ehv-bc", bc);
667    if (ret < 0) {
668        dev_err(bc->dev, "could not request tx irq %u (ret=%i)\n",
669               bc->tx_irq, ret);
670        free_irq(bc->rx_irq, bc);
671        return ret;
672    }
673
674    /* The TX IRQ is enabled only when we can't write all the data to the
675     * byte channel at once, so by default it's disabled.
676     */
677    disable_tx_interrupt(bc);
678
679    return 0;
680}
681
682static void ehv_bc_tty_port_shutdown(struct tty_port *port)
683{
684    struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port);
685
686    free_irq(bc->tx_irq, bc);
687    free_irq(bc->rx_irq, bc);
688}
689
690static const struct tty_port_operations ehv_bc_tty_port_ops = {
691    .activate = ehv_bc_tty_port_activate,
692    .shutdown = ehv_bc_tty_port_shutdown,
693};
694
695static int ehv_bc_tty_probe(struct platform_device *pdev)
696{
697    struct device_node *np = pdev->dev.of_node;
698    struct ehv_bc_data *bc;
699    const uint32_t *iprop;
700    unsigned int handle;
701    int ret;
702    static unsigned int index = 1;
703    unsigned int i;
704
705    iprop = of_get_property(np, "hv-handle", NULL);
706    if (!iprop) {
707        dev_err(&pdev->dev, "no 'hv-handle' property in %s node\n",
708            np->name);
709        return -ENODEV;
710    }
711
712    /* We already told the console layer that the index for the console
713     * device is zero, so we need to make sure that we use that index when
714     * we probe the console byte channel node.
715     */
716    handle = be32_to_cpu(*iprop);
717    i = (handle == stdout_bc) ? 0 : index++;
718    bc = &bcs[i];
719
720    bc->handle = handle;
721    bc->head = 0;
722    bc->tail = 0;
723    spin_lock_init(&bc->lock);
724
725    bc->rx_irq = irq_of_parse_and_map(np, 0);
726    bc->tx_irq = irq_of_parse_and_map(np, 1);
727    if ((bc->rx_irq == NO_IRQ) || (bc->tx_irq == NO_IRQ)) {
728        dev_err(&pdev->dev, "no 'interrupts' property in %s node\n",
729            np->name);
730        ret = -ENODEV;
731        goto error;
732    }
733
734    tty_port_init(&bc->port);
735    bc->port.ops = &ehv_bc_tty_port_ops;
736
737    bc->dev = tty_port_register_device(&bc->port, ehv_bc_driver, i,
738            &pdev->dev);
739    if (IS_ERR(bc->dev)) {
740        ret = PTR_ERR(bc->dev);
741        dev_err(&pdev->dev, "could not register tty (ret=%i)\n", ret);
742        goto error;
743    }
744
745    dev_set_drvdata(&pdev->dev, bc);
746
747    dev_info(&pdev->dev, "registered /dev/%s%u for byte channel %u\n",
748        ehv_bc_driver->name, i, bc->handle);
749
750    return 0;
751
752error:
753    tty_port_destroy(&bc->port);
754    irq_dispose_mapping(bc->tx_irq);
755    irq_dispose_mapping(bc->rx_irq);
756
757    memset(bc, 0, sizeof(struct ehv_bc_data));
758    return ret;
759}
760
761static int ehv_bc_tty_remove(struct platform_device *pdev)
762{
763    struct ehv_bc_data *bc = dev_get_drvdata(&pdev->dev);
764
765    tty_unregister_device(ehv_bc_driver, bc - bcs);
766
767    tty_port_destroy(&bc->port);
768    irq_dispose_mapping(bc->tx_irq);
769    irq_dispose_mapping(bc->rx_irq);
770
771    return 0;
772}
773
774static const struct of_device_id ehv_bc_tty_of_ids[] = {
775    { .compatible = "epapr,hv-byte-channel" },
776    {}
777};
778
779static struct platform_driver ehv_bc_tty_driver = {
780    .driver = {
781        .owner = THIS_MODULE,
782        .name = "ehv-bc",
783        .of_match_table = ehv_bc_tty_of_ids,
784    },
785    .probe = ehv_bc_tty_probe,
786    .remove = ehv_bc_tty_remove,
787};
788
789/**
790 * ehv_bc_init - ePAPR hypervisor byte channel driver initialization
791 *
792 * This function is called when this module is loaded.
793 */
794static int __init ehv_bc_init(void)
795{
796    struct device_node *np;
797    unsigned int count = 0; /* Number of elements in bcs[] */
798    int ret;
799
800    pr_info("ePAPR hypervisor byte channel driver\n");
801
802    /* Count the number of byte channels */
803    for_each_compatible_node(np, NULL, "epapr,hv-byte-channel")
804        count++;
805
806    if (!count)
807        return -ENODEV;
808
809    /* The array index of an element in bcs[] is the same as the tty index
810     * for that element. If you know the address of an element in the
811     * array, then you can use pointer math (e.g. "bc - bcs") to get its
812     * tty index.
813     */
814    bcs = kzalloc(count * sizeof(struct ehv_bc_data), GFP_KERNEL);
815    if (!bcs)
816        return -ENOMEM;
817
818    ehv_bc_driver = alloc_tty_driver(count);
819    if (!ehv_bc_driver) {
820        ret = -ENOMEM;
821        goto error;
822    }
823
824    ehv_bc_driver->driver_name = "ehv-bc";
825    ehv_bc_driver->name = ehv_bc_console.name;
826    ehv_bc_driver->type = TTY_DRIVER_TYPE_CONSOLE;
827    ehv_bc_driver->subtype = SYSTEM_TYPE_CONSOLE;
828    ehv_bc_driver->init_termios = tty_std_termios;
829    ehv_bc_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
830    tty_set_operations(ehv_bc_driver, &ehv_bc_ops);
831
832    ret = tty_register_driver(ehv_bc_driver);
833    if (ret) {
834        pr_err("ehv-bc: could not register tty driver (ret=%i)\n", ret);
835        goto error;
836    }
837
838    ret = platform_driver_register(&ehv_bc_tty_driver);
839    if (ret) {
840        pr_err("ehv-bc: could not register platform driver (ret=%i)\n",
841               ret);
842        goto error;
843    }
844
845    return 0;
846
847error:
848    if (ehv_bc_driver) {
849        tty_unregister_driver(ehv_bc_driver);
850        put_tty_driver(ehv_bc_driver);
851    }
852
853    kfree(bcs);
854
855    return ret;
856}
857
858
859/**
860 * ehv_bc_exit - ePAPR hypervisor byte channel driver termination
861 *
862 * This function is called when this driver is unloaded.
863 */
864static void __exit ehv_bc_exit(void)
865{
866    tty_unregister_driver(ehv_bc_driver);
867    put_tty_driver(ehv_bc_driver);
868    kfree(bcs);
869}
870
871module_init(ehv_bc_init);
872module_exit(ehv_bc_exit);
873
874MODULE_AUTHOR("Timur Tabi <timur@freescale.com>");
875MODULE_DESCRIPTION("ePAPR hypervisor byte channel driver");
876MODULE_LICENSE("GPL v2");
877

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