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1// SPDX-License-Identifier: GPL-2.0
2/* ePAPR hypervisor byte channel device driver
3 *
4 * Copyright 2009-2011 Freescale Semiconductor, Inc.
5 *
6 * Author: Timur Tabi <timur@freescale.com>
7 *
8 * This driver support three distinct interfaces, all of which are related to
9 * ePAPR hypervisor byte channels.
10 *
11 * 1) An early-console (udbg) driver. This provides early console output
12 * through a byte channel. The byte channel handle must be specified in a
13 * Kconfig option.
14 *
15 * 2) A normal console driver. Output is sent to the byte channel designated
16 * for stdout in the device tree. The console driver is for handling kernel
17 * printk calls.
18 *
19 * 3) A tty driver, which is used to handle user-space input and output. The
20 * byte channel used for the console is designated as the default tty.
21 */
22
23#include <linux/init.h>
24#include <linux/slab.h>
25#include <linux/err.h>
26#include <linux/interrupt.h>
27#include <linux/fs.h>
28#include <linux/poll.h>
29#include <asm/epapr_hcalls.h>
30#include <linux/of.h>
31#include <linux/of_irq.h>
32#include <linux/platform_device.h>
33#include <linux/cdev.h>
34#include <linux/console.h>
35#include <linux/tty.h>
36#include <linux/tty_flip.h>
37#include <linux/circ_buf.h>
38#include <asm/udbg.h>
39
40/* The size of the transmit circular buffer. This must be a power of two. */
41#define BUF_SIZE 2048
42
43/* Per-byte channel private data */
44struct ehv_bc_data {
45 struct device *dev;
46 struct tty_port port;
47 uint32_t handle;
48 unsigned int rx_irq;
49 unsigned int tx_irq;
50
51 spinlock_t lock; /* lock for transmit buffer */
52 unsigned char buf[BUF_SIZE]; /* transmit circular buffer */
53 unsigned int head; /* circular buffer head */
54 unsigned int tail; /* circular buffer tail */
55
56 int tx_irq_enabled; /* true == TX interrupt is enabled */
57};
58
59/* Array of byte channel objects */
60static struct ehv_bc_data *bcs;
61
62/* Byte channel handle for stdout (and stdin), taken from device tree */
63static unsigned int stdout_bc;
64
65/* Virtual IRQ for the byte channel handle for stdin, taken from device tree */
66static unsigned int stdout_irq;
67
68/**************************** SUPPORT FUNCTIONS ****************************/
69
70/*
71 * Enable the transmit interrupt
72 *
73 * Unlike a serial device, byte channels have no mechanism for disabling their
74 * own receive or transmit interrupts. To emulate that feature, we toggle
75 * the IRQ in the kernel.
76 *
77 * We cannot just blindly call enable_irq() or disable_irq(), because these
78 * calls are reference counted. This means that we cannot call enable_irq()
79 * if interrupts are already enabled. This can happen in two situations:
80 *
81 * 1. The tty layer makes two back-to-back calls to ehv_bc_tty_write()
82 * 2. A transmit interrupt occurs while executing ehv_bc_tx_dequeue()
83 *
84 * To work around this, we keep a flag to tell us if the IRQ is enabled or not.
85 */
86static void enable_tx_interrupt(struct ehv_bc_data *bc)
87{
88 if (!bc->tx_irq_enabled) {
89 enable_irq(bc->tx_irq);
90 bc->tx_irq_enabled = 1;
91 }
92}
93
94static void disable_tx_interrupt(struct ehv_bc_data *bc)
95{
96 if (bc->tx_irq_enabled) {
97 disable_irq_nosync(bc->tx_irq);
98 bc->tx_irq_enabled = 0;
99 }
100}
101
102/*
103 * find the byte channel handle to use for the console
104 *
105 * The byte channel to be used for the console is specified via a "stdout"
106 * property in the /chosen node.
107 */
108static int find_console_handle(void)
109{
110 struct device_node *np = of_stdout;
111 const uint32_t *iprop;
112
113 /* We don't care what the aliased node is actually called. We only
114 * care if it's compatible with "epapr,hv-byte-channel", because that
115 * indicates that it's a byte channel node.
116 */
117 if (!np || !of_device_is_compatible(np, "epapr,hv-byte-channel"))
118 return 0;
119
120 stdout_irq = irq_of_parse_and_map(np, 0);
121 if (stdout_irq == NO_IRQ) {
122 pr_err("ehv-bc: no 'interrupts' property in %pOF node\n", np);
123 return 0;
124 }
125
126 /*
127 * The 'hv-handle' property contains the handle for this byte channel.
128 */
129 iprop = of_get_property(np, "hv-handle", NULL);
130 if (!iprop) {
131 pr_err("ehv-bc: no 'hv-handle' property in %pOFn node\n",
132 np);
133 return 0;
134 }
135 stdout_bc = be32_to_cpu(*iprop);
136 return 1;
137}
138
139/*************************** EARLY CONSOLE DRIVER ***************************/
140
141#ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC
142
143/*
144 * send a byte to a byte channel, wait if necessary
145 *
146 * This function sends a byte to a byte channel, and it waits and
147 * retries if the byte channel is full. It returns if the character
148 * has been sent, or if some error has occurred.
149 *
150 */
151static void byte_channel_spin_send(const char data)
152{
153 int ret, count;
154
155 do {
156 count = 1;
157 ret = ev_byte_channel_send(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE,
158 &count, &data);
159 } while (ret == EV_EAGAIN);
160}
161
162/*
163 * The udbg subsystem calls this function to display a single character.
164 * We convert CR to a CR/LF.
165 */
166static void ehv_bc_udbg_putc(char c)
167{
168 if (c == '\n')
169 byte_channel_spin_send('\r');
170
171 byte_channel_spin_send(c);
172}
173
174/*
175 * early console initialization
176 *
177 * PowerPC kernels support an early printk console, also known as udbg.
178 * This function must be called via the ppc_md.init_early function pointer.
179 * At this point, the device tree has been unflattened, so we can obtain the
180 * byte channel handle for stdout.
181 *
182 * We only support displaying of characters (putc). We do not support
183 * keyboard input.
184 */
185void __init udbg_init_ehv_bc(void)
186{
187 unsigned int rx_count, tx_count;
188 unsigned int ret;
189
190 /* Verify the byte channel handle */
191 ret = ev_byte_channel_poll(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE,
192 &rx_count, &tx_count);
193 if (ret)
194 return;
195
196 udbg_putc = ehv_bc_udbg_putc;
197 register_early_udbg_console();
198
199 udbg_printf("ehv-bc: early console using byte channel handle %u\n",
200 CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE);
201}
202
203#endif
204
205/****************************** CONSOLE DRIVER ******************************/
206
207static struct tty_driver *ehv_bc_driver;
208
209/*
210 * Byte channel console sending worker function.
211 *
212 * For consoles, if the output buffer is full, we should just spin until it
213 * clears.
214 */
215static int ehv_bc_console_byte_channel_send(unsigned int handle, const char *s,
216 unsigned int count)
217{
218 unsigned int len;
219 int ret = 0;
220
221 while (count) {
222 len = min_t(unsigned int, count, EV_BYTE_CHANNEL_MAX_BYTES);
223 do {
224 ret = ev_byte_channel_send(handle, &len, s);
225 } while (ret == EV_EAGAIN);
226 count -= len;
227 s += len;
228 }
229
230 return ret;
231}
232
233/*
234 * write a string to the console
235 *
236 * This function gets called to write a string from the kernel, typically from
237 * a printk(). This function spins until all data is written.
238 *
239 * We copy the data to a temporary buffer because we need to insert a \r in
240 * front of every \n. It's more efficient to copy the data to the buffer than
241 * it is to make multiple hcalls for each character or each newline.
242 */
243static void ehv_bc_console_write(struct console *co, const char *s,
244 unsigned int count)
245{
246 char s2[EV_BYTE_CHANNEL_MAX_BYTES];
247 unsigned int i, j = 0;
248 char c;
249
250 for (i = 0; i < count; i++) {
251 c = *s++;
252
253 if (c == '\n')
254 s2[j++] = '\r';
255
256 s2[j++] = c;
257 if (j >= (EV_BYTE_CHANNEL_MAX_BYTES - 1)) {
258 if (ehv_bc_console_byte_channel_send(stdout_bc, s2, j))
259 return;
260 j = 0;
261 }
262 }
263
264 if (j)
265 ehv_bc_console_byte_channel_send(stdout_bc, s2, j);
266}
267
268/*
269 * When /dev/console is opened, the kernel iterates the console list looking
270 * for one with ->device and then calls that method. On success, it expects
271 * the passed-in int* to contain the minor number to use.
272 */
273static struct tty_driver *ehv_bc_console_device(struct console *co, int *index)
274{
275 *index = co->index;
276
277 return ehv_bc_driver;
278}
279
280static struct console ehv_bc_console = {
281 .name = "ttyEHV",
282 .write = ehv_bc_console_write,
283 .device = ehv_bc_console_device,
284 .flags = CON_PRINTBUFFER | CON_ENABLED,
285};
286
287/*
288 * Console initialization
289 *
290 * This is the first function that is called after the device tree is
291 * available, so here is where we determine the byte channel handle and IRQ for
292 * stdout/stdin, even though that information is used by the tty and character
293 * drivers.
294 */
295static int __init ehv_bc_console_init(void)
296{
297 if (!find_console_handle()) {
298 pr_debug("ehv-bc: stdout is not a byte channel\n");
299 return -ENODEV;
300 }
301
302#ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC
303 /* Print a friendly warning if the user chose the wrong byte channel
304 * handle for udbg.
305 */
306 if (stdout_bc != CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE)
307 pr_warn("ehv-bc: udbg handle %u is not the stdout handle\n",
308 CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE);
309#endif
310
311 /* add_preferred_console() must be called before register_console(),
312 otherwise it won't work. However, we don't want to enumerate all the
313 byte channels here, either, since we only care about one. */
314
315 add_preferred_console(ehv_bc_console.name, ehv_bc_console.index, NULL);
316 register_console(&ehv_bc_console);
317
318 pr_info("ehv-bc: registered console driver for byte channel %u\n",
319 stdout_bc);
320
321 return 0;
322}
323console_initcall(ehv_bc_console_init);
324
325/******************************** TTY DRIVER ********************************/
326
327/*
328 * byte channel receive interrupt handler
329 *
330 * This ISR is called whenever data is available on a byte channel.
331 */
332static irqreturn_t ehv_bc_tty_rx_isr(int irq, void *data)
333{
334 struct ehv_bc_data *bc = data;
335 unsigned int rx_count, tx_count, len;
336 int count;
337 char buffer[EV_BYTE_CHANNEL_MAX_BYTES];
338 int ret;
339
340 /* Find out how much data needs to be read, and then ask the TTY layer
341 * if it can handle that much. We want to ensure that every byte we
342 * read from the byte channel will be accepted by the TTY layer.
343 */
344 ev_byte_channel_poll(bc->handle, &rx_count, &tx_count);
345 count = tty_buffer_request_room(&bc->port, rx_count);
346
347 /* 'count' is the maximum amount of data the TTY layer can accept at
348 * this time. However, during testing, I was never able to get 'count'
349 * to be less than 'rx_count'. I'm not sure whether I'm calling it
350 * correctly.
351 */
352
353 while (count > 0) {
354 len = min_t(unsigned int, count, sizeof(buffer));
355
356 /* Read some data from the byte channel. This function will
357 * never return more than EV_BYTE_CHANNEL_MAX_BYTES bytes.
358 */
359 ev_byte_channel_receive(bc->handle, &len, buffer);
360
361 /* 'len' is now the amount of data that's been received. 'len'
362 * can't be zero, and most likely it's equal to one.
363 */
364
365 /* Pass the received data to the tty layer. */
366 ret = tty_insert_flip_string(&bc->port, buffer, len);
367
368 /* 'ret' is the number of bytes that the TTY layer accepted.
369 * If it's not equal to 'len', then it means the buffer is
370 * full, which should never happen. If it does happen, we can
371 * exit gracefully, but we drop the last 'len - ret' characters
372 * that we read from the byte channel.
373 */
374 if (ret != len)
375 break;
376
377 count -= len;
378 }
379
380 /* Tell the tty layer that we're done. */
381 tty_flip_buffer_push(&bc->port);
382
383 return IRQ_HANDLED;
384}
385
386/*
387 * dequeue the transmit buffer to the hypervisor
388 *
389 * This function, which can be called in interrupt context, dequeues as much
390 * data as possible from the transmit buffer to the byte channel.
391 */
392static void ehv_bc_tx_dequeue(struct ehv_bc_data *bc)
393{
394 unsigned int count;
395 unsigned int len, ret;
396 unsigned long flags;
397
398 do {
399 spin_lock_irqsave(&bc->lock, flags);
400 len = min_t(unsigned int,
401 CIRC_CNT_TO_END(bc->head, bc->tail, BUF_SIZE),
402 EV_BYTE_CHANNEL_MAX_BYTES);
403
404 ret = ev_byte_channel_send(bc->handle, &len, bc->buf + bc->tail);
405
406 /* 'len' is valid only if the return code is 0 or EV_EAGAIN */
407 if (!ret || (ret == EV_EAGAIN))
408 bc->tail = (bc->tail + len) & (BUF_SIZE - 1);
409
410 count = CIRC_CNT(bc->head, bc->tail, BUF_SIZE);
411 spin_unlock_irqrestore(&bc->lock, flags);
412 } while (count && !ret);
413
414 spin_lock_irqsave(&bc->lock, flags);
415 if (CIRC_CNT(bc->head, bc->tail, BUF_SIZE))
416 /*
417 * If we haven't emptied the buffer, then enable the TX IRQ.
418 * We'll get an interrupt when there's more room in the
419 * hypervisor's output buffer.
420 */
421 enable_tx_interrupt(bc);
422 else
423 disable_tx_interrupt(bc);
424 spin_unlock_irqrestore(&bc->lock, flags);
425}
426
427/*
428 * byte channel transmit interrupt handler
429 *
430 * This ISR is called whenever space becomes available for transmitting
431 * characters on a byte channel.
432 */
433static irqreturn_t ehv_bc_tty_tx_isr(int irq, void *data)
434{
435 struct ehv_bc_data *bc = data;
436
437 ehv_bc_tx_dequeue(bc);
438 tty_port_tty_wakeup(&bc->port);
439
440 return IRQ_HANDLED;
441}
442
443/*
444 * This function is called when the tty layer has data for us send. We store
445 * the data first in a circular buffer, and then dequeue as much of that data
446 * as possible.
447 *
448 * We don't need to worry about whether there is enough room in the buffer for
449 * all the data. The purpose of ehv_bc_tty_write_room() is to tell the tty
450 * layer how much data it can safely send to us. We guarantee that
451 * ehv_bc_tty_write_room() will never lie, so the tty layer will never send us
452 * too much data.
453 */
454static int ehv_bc_tty_write(struct tty_struct *ttys, const unsigned char *s,
455 int count)
456{
457 struct ehv_bc_data *bc = ttys->driver_data;
458 unsigned long flags;
459 unsigned int len;
460 unsigned int written = 0;
461
462 while (1) {
463 spin_lock_irqsave(&bc->lock, flags);
464 len = CIRC_SPACE_TO_END(bc->head, bc->tail, BUF_SIZE);
465 if (count < len)
466 len = count;
467 if (len) {
468 memcpy(bc->buf + bc->head, s, len);
469 bc->head = (bc->head + len) & (BUF_SIZE - 1);
470 }
471 spin_unlock_irqrestore(&bc->lock, flags);
472 if (!len)
473 break;
474
475 s += len;
476 count -= len;
477 written += len;
478 }
479
480 ehv_bc_tx_dequeue(bc);
481
482 return written;
483}
484
485/*
486 * This function can be called multiple times for a given tty_struct, which is
487 * why we initialize bc->ttys in ehv_bc_tty_port_activate() instead.
488 *
489 * The tty layer will still call this function even if the device was not
490 * registered (i.e. tty_register_device() was not called). This happens
491 * because tty_register_device() is optional and some legacy drivers don't
492 * use it. So we need to check for that.
493 */
494static int ehv_bc_tty_open(struct tty_struct *ttys, struct file *filp)
495{
496 struct ehv_bc_data *bc = &bcs[ttys->index];
497
498 if (!bc->dev)
499 return -ENODEV;
500
501 return tty_port_open(&bc->port, ttys, filp);
502}
503
504/*
505 * Amazingly, if ehv_bc_tty_open() returns an error code, the tty layer will
506 * still call this function to close the tty device. So we can't assume that
507 * the tty port has been initialized.
508 */
509static void ehv_bc_tty_close(struct tty_struct *ttys, struct file *filp)
510{
511 struct ehv_bc_data *bc = &bcs[ttys->index];
512
513 if (bc->dev)
514 tty_port_close(&bc->port, ttys, filp);
515}
516
517/*
518 * Return the amount of space in the output buffer
519 *
520 * This is actually a contract between the driver and the tty layer outlining
521 * how much write room the driver can guarantee will be sent OR BUFFERED. This
522 * driver MUST honor the return value.
523 */
524static int ehv_bc_tty_write_room(struct tty_struct *ttys)
525{
526 struct ehv_bc_data *bc = ttys->driver_data;
527 unsigned long flags;
528 int count;
529
530 spin_lock_irqsave(&bc->lock, flags);
531 count = CIRC_SPACE(bc->head, bc->tail, BUF_SIZE);
532 spin_unlock_irqrestore(&bc->lock, flags);
533
534 return count;
535}
536
537/*
538 * Stop sending data to the tty layer
539 *
540 * This function is called when the tty layer's input buffers are getting full,
541 * so the driver should stop sending it data. The easiest way to do this is to
542 * disable the RX IRQ, which will prevent ehv_bc_tty_rx_isr() from being
543 * called.
544 *
545 * The hypervisor will continue to queue up any incoming data. If there is any
546 * data in the queue when the RX interrupt is enabled, we'll immediately get an
547 * RX interrupt.
548 */
549static void ehv_bc_tty_throttle(struct tty_struct *ttys)
550{
551 struct ehv_bc_data *bc = ttys->driver_data;
552
553 disable_irq(bc->rx_irq);
554}
555
556/*
557 * Resume sending data to the tty layer
558 *
559 * This function is called after previously calling ehv_bc_tty_throttle(). The
560 * tty layer's input buffers now have more room, so the driver can resume
561 * sending it data.
562 */
563static void ehv_bc_tty_unthrottle(struct tty_struct *ttys)
564{
565 struct ehv_bc_data *bc = ttys->driver_data;
566
567 /* If there is any data in the queue when the RX interrupt is enabled,
568 * we'll immediately get an RX interrupt.
569 */
570 enable_irq(bc->rx_irq);
571}
572
573static void ehv_bc_tty_hangup(struct tty_struct *ttys)
574{
575 struct ehv_bc_data *bc = ttys->driver_data;
576
577 ehv_bc_tx_dequeue(bc);
578 tty_port_hangup(&bc->port);
579}
580
581/*
582 * TTY driver operations
583 *
584 * If we could ask the hypervisor how much data is still in the TX buffer, or
585 * at least how big the TX buffers are, then we could implement the
586 * .wait_until_sent and .chars_in_buffer functions.
587 */
588static const struct tty_operations ehv_bc_ops = {
589 .open = ehv_bc_tty_open,
590 .close = ehv_bc_tty_close,
591 .write = ehv_bc_tty_write,
592 .write_room = ehv_bc_tty_write_room,
593 .throttle = ehv_bc_tty_throttle,
594 .unthrottle = ehv_bc_tty_unthrottle,
595 .hangup = ehv_bc_tty_hangup,
596};
597
598/*
599 * initialize the TTY port
600 *
601 * This function will only be called once, no matter how many times
602 * ehv_bc_tty_open() is called. That's why we register the ISR here, and also
603 * why we initialize tty_struct-related variables here.
604 */
605static int ehv_bc_tty_port_activate(struct tty_port *port,
606 struct tty_struct *ttys)
607{
608 struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port);
609 int ret;
610
611 ttys->driver_data = bc;
612
613 ret = request_irq(bc->rx_irq, ehv_bc_tty_rx_isr, 0, "ehv-bc", bc);
614 if (ret < 0) {
615 dev_err(bc->dev, "could not request rx irq %u (ret=%i)\n",
616 bc->rx_irq, ret);
617 return ret;
618 }
619
620 /* request_irq also enables the IRQ */
621 bc->tx_irq_enabled = 1;
622
623 ret = request_irq(bc->tx_irq, ehv_bc_tty_tx_isr, 0, "ehv-bc", bc);
624 if (ret < 0) {
625 dev_err(bc->dev, "could not request tx irq %u (ret=%i)\n",
626 bc->tx_irq, ret);
627 free_irq(bc->rx_irq, bc);
628 return ret;
629 }
630
631 /* The TX IRQ is enabled only when we can't write all the data to the
632 * byte channel at once, so by default it's disabled.
633 */
634 disable_tx_interrupt(bc);
635
636 return 0;
637}
638
639static void ehv_bc_tty_port_shutdown(struct tty_port *port)
640{
641 struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port);
642
643 free_irq(bc->tx_irq, bc);
644 free_irq(bc->rx_irq, bc);
645}
646
647static const struct tty_port_operations ehv_bc_tty_port_ops = {
648 .activate = ehv_bc_tty_port_activate,
649 .shutdown = ehv_bc_tty_port_shutdown,
650};
651
652static int ehv_bc_tty_probe(struct platform_device *pdev)
653{
654 struct device_node *np = pdev->dev.of_node;
655 struct ehv_bc_data *bc;
656 const uint32_t *iprop;
657 unsigned int handle;
658 int ret;
659 static unsigned int index = 1;
660 unsigned int i;
661
662 iprop = of_get_property(np, "hv-handle", NULL);
663 if (!iprop) {
664 dev_err(&pdev->dev, "no 'hv-handle' property in %pOFn node\n",
665 np);
666 return -ENODEV;
667 }
668
669 /* We already told the console layer that the index for the console
670 * device is zero, so we need to make sure that we use that index when
671 * we probe the console byte channel node.
672 */
673 handle = be32_to_cpu(*iprop);
674 i = (handle == stdout_bc) ? 0 : index++;
675 bc = &bcs[i];
676
677 bc->handle = handle;
678 bc->head = 0;
679 bc->tail = 0;
680 spin_lock_init(&bc->lock);
681
682 bc->rx_irq = irq_of_parse_and_map(np, 0);
683 bc->tx_irq = irq_of_parse_and_map(np, 1);
684 if ((bc->rx_irq == NO_IRQ) || (bc->tx_irq == NO_IRQ)) {
685 dev_err(&pdev->dev, "no 'interrupts' property in %pOFn node\n",
686 np);
687 ret = -ENODEV;
688 goto error;
689 }
690
691 tty_port_init(&bc->port);
692 bc->port.ops = &ehv_bc_tty_port_ops;
693
694 bc->dev = tty_port_register_device(&bc->port, ehv_bc_driver, i,
695 &pdev->dev);
696 if (IS_ERR(bc->dev)) {
697 ret = PTR_ERR(bc->dev);
698 dev_err(&pdev->dev, "could not register tty (ret=%i)\n", ret);
699 goto error;
700 }
701
702 dev_set_drvdata(&pdev->dev, bc);
703
704 dev_info(&pdev->dev, "registered /dev/%s%u for byte channel %u\n",
705 ehv_bc_driver->name, i, bc->handle);
706
707 return 0;
708
709error:
710 tty_port_destroy(&bc->port);
711 irq_dispose_mapping(bc->tx_irq);
712 irq_dispose_mapping(bc->rx_irq);
713
714 memset(bc, 0, sizeof(struct ehv_bc_data));
715 return ret;
716}
717
718static const struct of_device_id ehv_bc_tty_of_ids[] = {
719 { .compatible = "epapr,hv-byte-channel" },
720 {}
721};
722
723static struct platform_driver ehv_bc_tty_driver = {
724 .driver = {
725 .name = "ehv-bc",
726 .of_match_table = ehv_bc_tty_of_ids,
727 .suppress_bind_attrs = true,
728 },
729 .probe = ehv_bc_tty_probe,
730};
731
732/**
733 * ehv_bc_init - ePAPR hypervisor byte channel driver initialization
734 *
735 * This function is called when this driver is loaded.
736 */
737static int __init ehv_bc_init(void)
738{
739 struct device_node *np;
740 unsigned int count = 0; /* Number of elements in bcs[] */
741 int ret;
742
743 pr_info("ePAPR hypervisor byte channel driver\n");
744
745 /* Count the number of byte channels */
746 for_each_compatible_node(np, NULL, "epapr,hv-byte-channel")
747 count++;
748
749 if (!count)
750 return -ENODEV;
751
752 /* The array index of an element in bcs[] is the same as the tty index
753 * for that element. If you know the address of an element in the
754 * array, then you can use pointer math (e.g. "bc - bcs") to get its
755 * tty index.
756 */
757 bcs = kcalloc(count, sizeof(struct ehv_bc_data), GFP_KERNEL);
758 if (!bcs)
759 return -ENOMEM;
760
761 ehv_bc_driver = alloc_tty_driver(count);
762 if (!ehv_bc_driver) {
763 ret = -ENOMEM;
764 goto err_free_bcs;
765 }
766
767 ehv_bc_driver->driver_name = "ehv-bc";
768 ehv_bc_driver->name = ehv_bc_console.name;
769 ehv_bc_driver->type = TTY_DRIVER_TYPE_CONSOLE;
770 ehv_bc_driver->subtype = SYSTEM_TYPE_CONSOLE;
771 ehv_bc_driver->init_termios = tty_std_termios;
772 ehv_bc_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
773 tty_set_operations(ehv_bc_driver, &ehv_bc_ops);
774
775 ret = tty_register_driver(ehv_bc_driver);
776 if (ret) {
777 pr_err("ehv-bc: could not register tty driver (ret=%i)\n", ret);
778 goto err_put_tty_driver;
779 }
780
781 ret = platform_driver_register(&ehv_bc_tty_driver);
782 if (ret) {
783 pr_err("ehv-bc: could not register platform driver (ret=%i)\n",
784 ret);
785 goto err_deregister_tty_driver;
786 }
787
788 return 0;
789
790err_deregister_tty_driver:
791 tty_unregister_driver(ehv_bc_driver);
792err_put_tty_driver:
793 put_tty_driver(ehv_bc_driver);
794err_free_bcs:
795 kfree(bcs);
796
797 return ret;
798}
799device_initcall(ehv_bc_init);
800

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