cregit-Linux how code gets into the kernel

Release 4.8 sound/firewire/lib.c

Directory: sound/firewire
/*
 * miscellaneous helper functions
 *
 * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
 * Licensed under the terms of the GNU General Public License, version 2.
 */

#include <linux/delay.h>
#include <linux/device.h>
#include <linux/firewire.h>
#include <linux/module.h>
#include <linux/slab.h>
#include "lib.h"


#define ERROR_RETRY_DELAY_MS	20

/**
 * snd_fw_transaction - send a request and wait for its completion
 * @unit: the driver's unit on the target device
 * @tcode: the transaction code
 * @offset: the address in the target's address space
 * @buffer: input/output data
 * @length: length of @buffer
 * @flags: use %FW_FIXED_GENERATION and add the generation value to attempt the
 *         request only in that generation; use %FW_QUIET to suppress error
 *         messages
 *
 * Submits an asynchronous request to the target device, and waits for the
 * response.  The node ID and the current generation are derived from @unit.
 * On a bus reset or an error, the transaction is retried a few times.
 * Returns zero on success, or a negative error code.
 */

int snd_fw_transaction(struct fw_unit *unit, int tcode, u64 offset, void *buffer, size_t length, unsigned int flags) { struct fw_device *device = fw_parent_device(unit); int generation, rcode, tries = 0; generation = flags & FW_GENERATION_MASK; for (;;) { if (!(flags & FW_FIXED_GENERATION)) { generation = device->generation; smp_rmb(); /* node_id vs. generation */ } rcode = fw_run_transaction(device->card, tcode, device->node_id, generation, device->max_speed, offset, buffer, length); if (rcode == RCODE_COMPLETE) return 0; if (rcode == RCODE_GENERATION && (flags & FW_FIXED_GENERATION)) return -EAGAIN; if (rcode_is_permanent_error(rcode) || ++tries >= 3) { if (!(flags & FW_QUIET)) dev_err(&unit->device, "transaction failed: %s\n", fw_rcode_string(rcode)); return -EIO; } msleep(ERROR_RETRY_DELAY_MS); } }

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EXPORT_SYMBOL(snd_fw_transaction); #define PROBE_DELAY_MS (2 * MSEC_PER_SEC) /** * snd_fw_schedule_registration - schedule work for sound card registration * @unit: an instance for unit on IEEE 1394 bus * @dwork: delayed work with callback function * * This function is not designed for general purposes. When new unit is * connected to IEEE 1394 bus, the bus is under bus-reset state because of * topological change. In this state, units tend to fail both of asynchronous * and isochronous communication. To avoid this problem, this function is used * to postpone sound card registration after the state. The callers must * set up instance of delayed work in advance. */
void snd_fw_schedule_registration(struct fw_unit *unit, struct delayed_work *dwork) { u64 now, delay; now = get_jiffies_64(); delay = fw_parent_device(unit)->card->reset_jiffies + msecs_to_jiffies(PROBE_DELAY_MS); if (time_after64(delay, now)) delay -= now; else delay = 0; mod_delayed_work(system_wq, dwork, delay); }

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EXPORT_SYMBOL(snd_fw_schedule_registration);
static void async_midi_port_callback(struct fw_card *card, int rcode, void *data, size_t length, void *callback_data) { struct snd_fw_async_midi_port *port = callback_data; struct snd_rawmidi_substream *substream = ACCESS_ONCE(port->substream); /* This port is closed. */ if (substream == NULL) return; if (rcode == RCODE_COMPLETE) snd_rawmidi_transmit_ack(substream, port->consume_bytes); else if (!rcode_is_permanent_error(rcode)) /* To start next transaction immediately for recovery. */ port->next_ktime = ktime_set(0, 0); else /* Don't continue processing. */ port->error = true; port->idling = true; if (!snd_rawmidi_transmit_empty(substream)) schedule_work(&port->work); }

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static void midi_port_work(struct work_struct *work) { struct snd_fw_async_midi_port *port = container_of(work, struct snd_fw_async_midi_port, work); struct snd_rawmidi_substream *substream = ACCESS_ONCE(port->substream); int generation; int type; /* Under transacting or error state. */ if (!port->idling || port->error) return; /* Nothing to do. */ if (substream == NULL || snd_rawmidi_transmit_empty(substream)) return; /* Do it in next chance. */ if (ktime_after(port->next_ktime, ktime_get())) { schedule_work(&port->work); return; } /* * Fill the buffer. The callee must use snd_rawmidi_transmit_peek(). * Later, snd_rawmidi_transmit_ack() is called. */ memset(port->buf, 0, port->len); port->consume_bytes = port->fill(substream, port->buf); if (port->consume_bytes <= 0) { /* Do it in next chance, immediately. */ if (port->consume_bytes == 0) { port->next_ktime = ktime_set(0, 0); schedule_work(&port->work); } else { /* Fatal error. */ port->error = true; } return; } /* Calculate type of transaction. */ if (port->len == 4) type = TCODE_WRITE_QUADLET_REQUEST; else type = TCODE_WRITE_BLOCK_REQUEST; /* Set interval to next transaction. */ port->next_ktime = ktime_add_ns(ktime_get(), port->consume_bytes * 8 * NSEC_PER_SEC / 31250); /* Start this transaction. */ port->idling = false; /* * In Linux FireWire core, when generation is updated with memory * barrier, node id has already been updated. In this module, After * this smp_rmb(), load/store instructions to memory are completed. * Thus, both of generation and node id are available with recent * values. This is a light-serialization solution to handle bus reset * events on IEEE 1394 bus. */ generation = port->parent->generation; smp_rmb(); fw_send_request(port->parent->card, &port->transaction, type, port->parent->node_id, generation, port->parent->max_speed, port->addr, port->buf, port->len, async_midi_port_callback, port); }

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/** * snd_fw_async_midi_port_init - initialize asynchronous MIDI port structure * @port: the asynchronous MIDI port to initialize * @unit: the target of the asynchronous transaction * @addr: the address to which transactions are transferred * @len: the length of transaction * @fill: the callback function to fill given buffer, and returns the * number of consumed bytes for MIDI message. * */
int snd_fw_async_midi_port_init(struct snd_fw_async_midi_port *port, struct fw_unit *unit, u64 addr, unsigned int len, snd_fw_async_midi_port_fill fill) { port->len = DIV_ROUND_UP(len, 4) * 4; port->buf = kzalloc(port->len, GFP_KERNEL); if (port->buf == NULL) return -ENOMEM; port->parent = fw_parent_device(unit); port->addr = addr; port->fill = fill; port->idling = true; port->next_ktime = ktime_set(0, 0); port->error = false; INIT_WORK(&port->work, midi_port_work); return 0; }

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EXPORT_SYMBOL(snd_fw_async_midi_port_init); /** * snd_fw_async_midi_port_destroy - free asynchronous MIDI port structure * @port: the asynchronous MIDI port structure */
void snd_fw_async_midi_port_destroy(struct snd_fw_async_midi_port *port) { snd_fw_async_midi_port_finish(port); cancel_work_sync(&port->work); kfree(port->buf); }

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EXPORT_SYMBOL(snd_fw_async_midi_port_destroy); MODULE_DESCRIPTION("FireWire audio helper functions"); MODULE_AUTHOR("Clemens Ladisch <clemens@ladisch.de>"); MODULE_LICENSE("GPL v2");

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Directory: sound/firewire
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