Version:  2.0.40 2.2.26 2.4.37 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0

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

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