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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 <[email protected]>
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 u8 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) {
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
139static unsigned int local_ev_byte_channel_send(unsigned int handle,
140 unsigned int *count,
141 const u8 *p)
142{
143 u8 buffer[EV_BYTE_CHANNEL_MAX_BYTES];
144 unsigned int c = *count;
145
146 /*
147 * ev_byte_channel_send() expects at least EV_BYTE_CHANNEL_MAX_BYTES
148 * (16 B) in the buffer. Fake it using a local buffer if needed.
149 */
150 if (c < sizeof(buffer)) {
151 memcpy_and_pad(buffer, sizeof(buffer), p, c, 0);
152 p = buffer;
153 }
154 return ev_byte_channel_send(handle, count, p);
155}
156
157/*************************** EARLY CONSOLE DRIVER ***************************/
158
159#ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC
160
161/*
162 * send a byte to a byte channel, wait if necessary
163 *
164 * This function sends a byte to a byte channel, and it waits and
165 * retries if the byte channel is full. It returns if the character
166 * has been sent, or if some error has occurred.
167 *
168 */
169static void byte_channel_spin_send(const u8 data)
170{
171 int ret, count;
172
173 do {
174 count = 1;
175 ret = local_ev_byte_channel_send(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE,
176 &count, &data);
177 } while (ret == EV_EAGAIN);
178}
179
180/*
181 * The udbg subsystem calls this function to display a single character.
182 * We convert CR to a CR/LF.
183 */
184static void ehv_bc_udbg_putc(char c)
185{
186 if (c == '\n')
187 byte_channel_spin_send('\r');
188
189 byte_channel_spin_send(c);
190}
191
192/*
193 * early console initialization
194 *
195 * PowerPC kernels support an early printk console, also known as udbg.
196 * This function must be called via the ppc_md.init_early function pointer.
197 * At this point, the device tree has been unflattened, so we can obtain the
198 * byte channel handle for stdout.
199 *
200 * We only support displaying of characters (putc). We do not support
201 * keyboard input.
202 */
203void __init udbg_init_ehv_bc(void)
204{
205 unsigned int rx_count, tx_count;
206 unsigned int ret;
207
208 /* Verify the byte channel handle */
209 ret = ev_byte_channel_poll(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE,
210 &rx_count, &tx_count);
211 if (ret)
212 return;
213
214 udbg_putc = ehv_bc_udbg_putc;
215 register_early_udbg_console();
216
217 udbg_printf("ehv-bc: early console using byte channel handle %u\n",
218 CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE);
219}
220
221#endif
222
223/****************************** CONSOLE DRIVER ******************************/
224
225static struct tty_driver *ehv_bc_driver;
226
227/*
228 * Byte channel console sending worker function.
229 *
230 * For consoles, if the output buffer is full, we should just spin until it
231 * clears.
232 */
233static int ehv_bc_console_byte_channel_send(unsigned int handle, const char *s,
234 unsigned int count)
235{
236 unsigned int len;
237 int ret = 0;
238
239 while (count) {
240 len = min_t(unsigned int, count, EV_BYTE_CHANNEL_MAX_BYTES);
241 do {
242 ret = local_ev_byte_channel_send(handle, &len, s);
243 } while (ret == EV_EAGAIN);
244 count -= len;
245 s += len;
246 }
247
248 return ret;
249}
250
251/*
252 * write a string to the console
253 *
254 * This function gets called to write a string from the kernel, typically from
255 * a printk(). This function spins until all data is written.
256 *
257 * We copy the data to a temporary buffer because we need to insert a \r in
258 * front of every \n. It's more efficient to copy the data to the buffer than
259 * it is to make multiple hcalls for each character or each newline.
260 */
261static void ehv_bc_console_write(struct console *co, const char *s,
262 unsigned int count)
263{
264 char s2[EV_BYTE_CHANNEL_MAX_BYTES];
265 unsigned int i, j = 0;
266 char c;
267
268 for (i = 0; i < count; i++) {
269 c = *s++;
270
271 if (c == '\n')
272 s2[j++] = '\r';
273
274 s2[j++] = c;
275 if (j >= (EV_BYTE_CHANNEL_MAX_BYTES - 1)) {
276 if (ehv_bc_console_byte_channel_send(stdout_bc, s2, j))
277 return;
278 j = 0;
279 }
280 }
281
282 if (j)
283 ehv_bc_console_byte_channel_send(stdout_bc, s2, j);
284}
285
286/*
287 * When /dev/console is opened, the kernel iterates the console list looking
288 * for one with ->device and then calls that method. On success, it expects
289 * the passed-in int* to contain the minor number to use.
290 */
291static struct tty_driver *ehv_bc_console_device(struct console *co, int *index)
292{
293 *index = co->index;
294
295 return ehv_bc_driver;
296}
297
298static struct console ehv_bc_console = {
299 .name = "ttyEHV",
300 .write = ehv_bc_console_write,
301 .device = ehv_bc_console_device,
302 .flags = CON_PRINTBUFFER | CON_ENABLED,
303};
304
305/*
306 * Console initialization
307 *
308 * This is the first function that is called after the device tree is
309 * available, so here is where we determine the byte channel handle and IRQ for
310 * stdout/stdin, even though that information is used by the tty and character
311 * drivers.
312 */
313static int __init ehv_bc_console_init(void)
314{
315 if (!find_console_handle()) {
316 pr_debug("ehv-bc: stdout is not a byte channel\n");
317 return -ENODEV;
318 }
319
320#ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC
321 /* Print a friendly warning if the user chose the wrong byte channel
322 * handle for udbg.
323 */
324 if (stdout_bc != CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE)
325 pr_warn("ehv-bc: udbg handle %u is not the stdout handle\n",
326 CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE);
327#endif
328
329 /* add_preferred_console() must be called before register_console(),
330 otherwise it won't work. However, we don't want to enumerate all the
331 byte channels here, either, since we only care about one. */
332
333 add_preferred_console(ehv_bc_console.name, ehv_bc_console.index, NULL);
334 register_console(&ehv_bc_console);
335
336 pr_info("ehv-bc: registered console driver for byte channel %u\n",
337 stdout_bc);
338
339 return 0;
340}
341console_initcall(ehv_bc_console_init);
342
343/******************************** TTY DRIVER ********************************/
344
345/*
346 * byte channel receive interrupt handler
347 *
348 * This ISR is called whenever data is available on a byte channel.
349 */
350static irqreturn_t ehv_bc_tty_rx_isr(int irq, void *data)
351{
352 struct ehv_bc_data *bc = data;
353 unsigned int rx_count, tx_count, len;
354 int count;
355 char buffer[EV_BYTE_CHANNEL_MAX_BYTES];
356 int ret;
357
358 /* Find out how much data needs to be read, and then ask the TTY layer
359 * if it can handle that much. We want to ensure that every byte we
360 * read from the byte channel will be accepted by the TTY layer.
361 */
362 ev_byte_channel_poll(bc->handle, &rx_count, &tx_count);
363 count = tty_buffer_request_room(&bc->port, rx_count);
364
365 /* 'count' is the maximum amount of data the TTY layer can accept at
366 * this time. However, during testing, I was never able to get 'count'
367 * to be less than 'rx_count'. I'm not sure whether I'm calling it
368 * correctly.
369 */
370
371 while (count > 0) {
372 len = min_t(unsigned int, count, sizeof(buffer));
373
374 /* Read some data from the byte channel. This function will
375 * never return more than EV_BYTE_CHANNEL_MAX_BYTES bytes.
376 */
377 ev_byte_channel_receive(bc->handle, &len, buffer);
378
379 /* 'len' is now the amount of data that's been received. 'len'
380 * can't be zero, and most likely it's equal to one.
381 */
382
383 /* Pass the received data to the tty layer. */
384 ret = tty_insert_flip_string(&bc->port, buffer, len);
385
386 /* 'ret' is the number of bytes that the TTY layer accepted.
387 * If it's not equal to 'len', then it means the buffer is
388 * full, which should never happen. If it does happen, we can
389 * exit gracefully, but we drop the last 'len - ret' characters
390 * that we read from the byte channel.
391 */
392 if (ret != len)
393 break;
394
395 count -= len;
396 }
397
398 /* Tell the tty layer that we're done. */
399 tty_flip_buffer_push(&bc->port);
400
401 return IRQ_HANDLED;
402}
403
404/*
405 * dequeue the transmit buffer to the hypervisor
406 *
407 * This function, which can be called in interrupt context, dequeues as much
408 * data as possible from the transmit buffer to the byte channel.
409 */
410static void ehv_bc_tx_dequeue(struct ehv_bc_data *bc)
411{
412 unsigned int count;
413 unsigned int len, ret;
414 unsigned long flags;
415
416 do {
417 spin_lock_irqsave(&bc->lock, flags);
418 len = min_t(unsigned int,
419 CIRC_CNT_TO_END(bc->head, bc->tail, BUF_SIZE),
420 EV_BYTE_CHANNEL_MAX_BYTES);
421
422 ret = local_ev_byte_channel_send(bc->handle, &len, bc->buf + bc->tail);
423
424 /* 'len' is valid only if the return code is 0 or EV_EAGAIN */
425 if (!ret || (ret == EV_EAGAIN))
426 bc->tail = (bc->tail + len) & (BUF_SIZE - 1);
427
428 count = CIRC_CNT(bc->head, bc->tail, BUF_SIZE);
429 spin_unlock_irqrestore(&bc->lock, flags);
430 } while (count && !ret);
431
432 spin_lock_irqsave(&bc->lock, flags);
433 if (CIRC_CNT(bc->head, bc->tail, BUF_SIZE))
434 /*
435 * If we haven't emptied the buffer, then enable the TX IRQ.
436 * We'll get an interrupt when there's more room in the
437 * hypervisor's output buffer.
438 */
439 enable_tx_interrupt(bc);
440 else
441 disable_tx_interrupt(bc);
442 spin_unlock_irqrestore(&bc->lock, flags);
443}
444
445/*
446 * byte channel transmit interrupt handler
447 *
448 * This ISR is called whenever space becomes available for transmitting
449 * characters on a byte channel.
450 */
451static irqreturn_t ehv_bc_tty_tx_isr(int irq, void *data)
452{
453 struct ehv_bc_data *bc = data;
454
455 ehv_bc_tx_dequeue(bc);
456 tty_port_tty_wakeup(&bc->port);
457
458 return IRQ_HANDLED;
459}
460
461/*
462 * This function is called when the tty layer has data for us send. We store
463 * the data first in a circular buffer, and then dequeue as much of that data
464 * as possible.
465 *
466 * We don't need to worry about whether there is enough room in the buffer for
467 * all the data. The purpose of ehv_bc_tty_write_room() is to tell the tty
468 * layer how much data it can safely send to us. We guarantee that
469 * ehv_bc_tty_write_room() will never lie, so the tty layer will never send us
470 * too much data.
471 */
472static ssize_t ehv_bc_tty_write(struct tty_struct *ttys, const u8 *s,
473 size_t count)
474{
475 struct ehv_bc_data *bc = ttys->driver_data;
476 unsigned long flags;
477 size_t len, written = 0;
478
479 while (1) {
480 spin_lock_irqsave(&bc->lock, flags);
481 len = CIRC_SPACE_TO_END(bc->head, bc->tail, BUF_SIZE);
482 if (count < len)
483 len = count;
484 if (len) {
485 memcpy(bc->buf + bc->head, s, len);
486 bc->head = (bc->head + len) & (BUF_SIZE - 1);
487 }
488 spin_unlock_irqrestore(&bc->lock, flags);
489 if (!len)
490 break;
491
492 s += len;
493 count -= len;
494 written += len;
495 }
496
497 ehv_bc_tx_dequeue(bc);
498
499 return written;
500}
501
502/*
503 * This function can be called multiple times for a given tty_struct, which is
504 * why we initialize bc->ttys in ehv_bc_tty_port_activate() instead.
505 *
506 * The tty layer will still call this function even if the device was not
507 * registered (i.e. tty_register_device() was not called). This happens
508 * because tty_register_device() is optional and some legacy drivers don't
509 * use it. So we need to check for that.
510 */
511static int ehv_bc_tty_open(struct tty_struct *ttys, struct file *filp)
512{
513 struct ehv_bc_data *bc = &bcs[ttys->index];
514
515 if (!bc->dev)
516 return -ENODEV;
517
518 return tty_port_open(&bc->port, ttys, filp);
519}
520
521/*
522 * Amazingly, if ehv_bc_tty_open() returns an error code, the tty layer will
523 * still call this function to close the tty device. So we can't assume that
524 * the tty port has been initialized.
525 */
526static void ehv_bc_tty_close(struct tty_struct *ttys, struct file *filp)
527{
528 struct ehv_bc_data *bc = &bcs[ttys->index];
529
530 if (bc->dev)
531 tty_port_close(&bc->port, ttys, filp);
532}
533
534/*
535 * Return the amount of space in the output buffer
536 *
537 * This is actually a contract between the driver and the tty layer outlining
538 * how much write room the driver can guarantee will be sent OR BUFFERED. This
539 * driver MUST honor the return value.
540 */
541static unsigned int ehv_bc_tty_write_room(struct tty_struct *ttys)
542{
543 struct ehv_bc_data *bc = ttys->driver_data;
544 unsigned long flags;
545 unsigned int count;
546
547 spin_lock_irqsave(&bc->lock, flags);
548 count = CIRC_SPACE(bc->head, bc->tail, BUF_SIZE);
549 spin_unlock_irqrestore(&bc->lock, flags);
550
551 return count;
552}
553
554/*
555 * Stop sending data to the tty layer
556 *
557 * This function is called when the tty layer's input buffers are getting full,
558 * so the driver should stop sending it data. The easiest way to do this is to
559 * disable the RX IRQ, which will prevent ehv_bc_tty_rx_isr() from being
560 * called.
561 *
562 * The hypervisor will continue to queue up any incoming data. If there is any
563 * data in the queue when the RX interrupt is enabled, we'll immediately get an
564 * RX interrupt.
565 */
566static void ehv_bc_tty_throttle(struct tty_struct *ttys)
567{
568 struct ehv_bc_data *bc = ttys->driver_data;
569
570 disable_irq(bc->rx_irq);
571}
572
573/*
574 * Resume sending data to the tty layer
575 *
576 * This function is called after previously calling ehv_bc_tty_throttle(). The
577 * tty layer's input buffers now have more room, so the driver can resume
578 * sending it data.
579 */
580static void ehv_bc_tty_unthrottle(struct tty_struct *ttys)
581{
582 struct ehv_bc_data *bc = ttys->driver_data;
583
584 /* If there is any data in the queue when the RX interrupt is enabled,
585 * we'll immediately get an RX interrupt.
586 */
587 enable_irq(bc->rx_irq);
588}
589
590static void ehv_bc_tty_hangup(struct tty_struct *ttys)
591{
592 struct ehv_bc_data *bc = ttys->driver_data;
593
594 ehv_bc_tx_dequeue(bc);
595 tty_port_hangup(&bc->port);
596}
597
598/*
599 * TTY driver operations
600 *
601 * If we could ask the hypervisor how much data is still in the TX buffer, or
602 * at least how big the TX buffers are, then we could implement the
603 * .wait_until_sent and .chars_in_buffer functions.
604 */
605static const struct tty_operations ehv_bc_ops = {
606 .open = ehv_bc_tty_open,
607 .close = ehv_bc_tty_close,
608 .write = ehv_bc_tty_write,
609 .write_room = ehv_bc_tty_write_room,
610 .throttle = ehv_bc_tty_throttle,
611 .unthrottle = ehv_bc_tty_unthrottle,
612 .hangup = ehv_bc_tty_hangup,
613};
614
615/*
616 * initialize the TTY port
617 *
618 * This function will only be called once, no matter how many times
619 * ehv_bc_tty_open() is called. That's why we register the ISR here, and also
620 * why we initialize tty_struct-related variables here.
621 */
622static int ehv_bc_tty_port_activate(struct tty_port *port,
623 struct tty_struct *ttys)
624{
625 struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port);
626 int ret;
627
628 ttys->driver_data = bc;
629
630 ret = request_irq(bc->rx_irq, ehv_bc_tty_rx_isr, 0, "ehv-bc", bc);
631 if (ret < 0) {
632 dev_err(bc->dev, "could not request rx irq %u (ret=%i)\n",
633 bc->rx_irq, ret);
634 return ret;
635 }
636
637 /* request_irq also enables the IRQ */
638 bc->tx_irq_enabled = 1;
639
640 ret = request_irq(bc->tx_irq, ehv_bc_tty_tx_isr, 0, "ehv-bc", bc);
641 if (ret < 0) {
642 dev_err(bc->dev, "could not request tx irq %u (ret=%i)\n",
643 bc->tx_irq, ret);
644 free_irq(bc->rx_irq, bc);
645 return ret;
646 }
647
648 /* The TX IRQ is enabled only when we can't write all the data to the
649 * byte channel at once, so by default it's disabled.
650 */
651 disable_tx_interrupt(bc);
652
653 return 0;
654}
655
656static void ehv_bc_tty_port_shutdown(struct tty_port *port)
657{
658 struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port);
659
660 free_irq(bc->tx_irq, bc);
661 free_irq(bc->rx_irq, bc);
662}
663
664static const struct tty_port_operations ehv_bc_tty_port_ops = {
665 .activate = ehv_bc_tty_port_activate,
666 .shutdown = ehv_bc_tty_port_shutdown,
667};
668
669static int ehv_bc_tty_probe(struct platform_device *pdev)
670{
671 struct device_node *np = pdev->dev.of_node;
672 struct ehv_bc_data *bc;
673 const uint32_t *iprop;
674 unsigned int handle;
675 int ret;
676 static unsigned int index = 1;
677 unsigned int i;
678
679 iprop = of_get_property(np, "hv-handle", NULL);
680 if (!iprop) {
681 dev_err(&pdev->dev, "no 'hv-handle' property in %pOFn node\n",
682 np);
683 return -ENODEV;
684 }
685
686 /* We already told the console layer that the index for the console
687 * device is zero, so we need to make sure that we use that index when
688 * we probe the console byte channel node.
689 */
690 handle = be32_to_cpu(*iprop);
691 i = (handle == stdout_bc) ? 0 : index++;
692 bc = &bcs[i];
693
694 bc->handle = handle;
695 bc->head = 0;
696 bc->tail = 0;
697 spin_lock_init(&bc->lock);
698
699 bc->rx_irq = irq_of_parse_and_map(np, 0);
700 bc->tx_irq = irq_of_parse_and_map(np, 1);
701 if (!bc->rx_irq || !bc->tx_irq) {
702 dev_err(&pdev->dev, "no 'interrupts' property in %pOFn node\n",
703 np);
704 ret = -ENODEV;
705 goto error;
706 }
707
708 tty_port_init(&bc->port);
709 bc->port.ops = &ehv_bc_tty_port_ops;
710
711 bc->dev = tty_port_register_device(&bc->port, ehv_bc_driver, i,
712 &pdev->dev);
713 if (IS_ERR(bc->dev)) {
714 ret = PTR_ERR(bc->dev);
715 dev_err(&pdev->dev, "could not register tty (ret=%i)\n", ret);
716 goto error;
717 }
718
719 dev_set_drvdata(&pdev->dev, bc);
720
721 dev_info(&pdev->dev, "registered /dev/%s%u for byte channel %u\n",
722 ehv_bc_driver->name, i, bc->handle);
723
724 return 0;
725
726error:
727 tty_port_destroy(&bc->port);
728 irq_dispose_mapping(bc->tx_irq);
729 irq_dispose_mapping(bc->rx_irq);
730
731 memset(bc, 0, sizeof(struct ehv_bc_data));
732 return ret;
733}
734
735static const struct of_device_id ehv_bc_tty_of_ids[] = {
736 { .compatible = "epapr,hv-byte-channel" },
737 {}
738};
739
740static struct platform_driver ehv_bc_tty_driver = {
741 .driver = {
742 .name = "ehv-bc",
743 .of_match_table = ehv_bc_tty_of_ids,
744 .suppress_bind_attrs = true,
745 },
746 .probe = ehv_bc_tty_probe,
747};
748
749/**
750 * ehv_bc_init - ePAPR hypervisor byte channel driver initialization
751 *
752 * This function is called when this driver is loaded.
753 */
754static int __init ehv_bc_init(void)
755{
756 struct tty_driver *driver;
757 struct device_node *np;
758 unsigned int count = 0; /* Number of elements in bcs[] */
759 int ret;
760
761 pr_info("ePAPR hypervisor byte channel driver\n");
762
763 /* Count the number of byte channels */
764 for_each_compatible_node(np, NULL, "epapr,hv-byte-channel")
765 count++;
766
767 if (!count)
768 return -ENODEV;
769
770 /* The array index of an element in bcs[] is the same as the tty index
771 * for that element. If you know the address of an element in the
772 * array, then you can use pointer math (e.g. "bc - bcs") to get its
773 * tty index.
774 */
775 bcs = kzalloc_objs(struct ehv_bc_data, count);
776 if (!bcs)
777 return -ENOMEM;
778
779 driver = tty_alloc_driver(count, TTY_DRIVER_REAL_RAW |
780 TTY_DRIVER_DYNAMIC_DEV);
781 if (IS_ERR(driver)) {
782 ret = PTR_ERR(driver);
783 goto err_free_bcs;
784 }
785
786 driver->driver_name = "ehv-bc";
787 driver->name = ehv_bc_console.name;
788 driver->type = TTY_DRIVER_TYPE_CONSOLE;
789 driver->subtype = SYSTEM_TYPE_CONSOLE;
790 driver->init_termios = tty_std_termios;
791 tty_set_operations(driver, &ehv_bc_ops);
792
793 ret = tty_register_driver(driver);
794 if (ret) {
795 pr_err("ehv-bc: could not register tty driver (ret=%i)\n", ret);
796 goto err_tty_driver_kref_put;
797 }
798
799 ehv_bc_driver = driver;
800
801 ret = platform_driver_register(&ehv_bc_tty_driver);
802 if (ret) {
803 pr_err("ehv-bc: could not register platform driver (ret=%i)\n",
804 ret);
805 goto err_deregister_tty_driver;
806 }
807
808 return 0;
809
810err_deregister_tty_driver:
811 ehv_bc_driver = NULL;
812 tty_unregister_driver(driver);
813err_tty_driver_kref_put:
814 tty_driver_kref_put(driver);
815err_free_bcs:
816 kfree(bcs);
817
818 return ret;
819}
820device_initcall(ehv_bc_init);