Version:  2.0.40 2.2.26 2.4.37 3.0 3.1 3.2 3.3 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

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

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