drivers/most/most_cdev.c


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73# SPDX-License-Identifier: GPL-2.0
#
# Kbuild for top-level directory of the kernel
# This file takes care of the following:
# 1) Generate bounds.h
# 2) Generate timeconst.h
# 3) Generate asm-offsets.h (may need bounds.h and timeconst.h)
# 4) Check for missing system calls
# 5) Generate constants.py (may need bounds.h)

#####
# 1) Generate bounds.h

bounds-file := include/generated/bounds.h

always  := $(bounds-file)
targets := kernel/bounds.s

# We use internal kbuild rules to avoid the "is up to date" message from make
kernel/bounds.s: kernel/bounds.c FORCE
	$(call if_changed_dep,cc_s_c)

$(obj)/$(bounds-file): kernel/bounds.s FORCE
	$(call filechk,offsets,__LINUX_BOUNDS_H__)

#####
# 2) Generate timeconst.h

timeconst-file := include/generated/timeconst.h

targets += $(timeconst-file)

quiet_cmd_gentimeconst = GEN     $@
define cmd_gentimeconst
	(echo $(CONFIG_HZ) | bc -q $< ) > $@
endef
define filechk_gentimeconst
	(echo $(CONFIG_HZ) | bc -q $< )
endef

$(obj)/$(timeconst-file): kernel/time/timeconst.bc FORCE
	$(call filechk,gentimeconst)

#####
# 3) Generate asm-offsets.h
#

offsets-file := include/generated/asm-offsets.h

always  += $(offsets-file)
targets += arch/$(SRCARCH)/kernel/asm-offsets.s

# We use internal kbuild rules to avoid the "is up to date" message from make
arch/$(SRCARCH)/kernel/asm-offsets.s: arch/$(SRCARCH)/kernel/asm-offsets.c \
                                      $(obj)/$(timeconst-file) $(obj)/$(bounds-file) FORCE
	$(call if_changed_dep,cc_s_c)

$(obj)/$(offsets-file): arch/$(SRCARCH)/kernel/asm-offsets.s FORCE
	$(call filechk,offsets,__ASM_OFFSETS_H__)

#####
# 4) Check for missing system calls
#

always += missing-syscalls
targets += missing-syscalls

quiet_cmd_syscalls = CALL    $<
      cmd_syscalls = $(CONFIG_SHELL) $< $(CC) $(c_flags) $(missing_syscalls_flags)

missing-syscalls: scripts/checksyscalls.sh $(offsets-file) FORCE
	$(call cmd,syscalls)

#####
# 5) Generate constants for Python GDB integration
#

extra-$(CONFIG_GDB_SCRIPTS) += build_constants_py

build_constants_py: $(obj)/$(timeconst-file) $(obj)/$(bounds-file)
	@$(MAKE) $(build)=scripts/gdb/linux $@

# Keep these three files during make clean
no-clean-files := $(bounds-file) $(offsets-file) $(timeconst-file)
// SPDX-License-Identifier: GPL-2.0
/*
 * cdev.c - Character device component for Mostcore
 *
 * Copyright (C) 2013-2015 Microchip Technology Germany II GmbH & Co. KG
 */

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/device.h>
#include <linux/cdev.h>
#include <linux/poll.h>
#include <linux/kfifo.h>
#include <linux/uaccess.h>
#include <linux/idr.h>
#include <linux/most.h>

#define CHRDEV_REGION_SIZE 50

static struct cdev_component {
	dev_t devno;
	struct ida minor_id;
	unsigned int major;
	struct class *class;
	struct most_component cc;
} comp;

struct comp_channel {
	wait_queue_head_t wq;
	spinlock_t unlink;	/* synchronization lock to unlink channels */
	struct cdev cdev;
	struct device *dev;
	struct mutex io_mutex;
	struct most_interface *iface;
	struct most_channel_config *cfg;
	unsigned int channel_id;
	dev_t devno;
	size_t mbo_offs;
	DECLARE_KFIFO_PTR(fifo, typeof(struct mbo *));
	int access_ref;
	struct list_head list;
};

#define to_channel(d) container_of(d, struct comp_channel, cdev)
static struct list_head channel_list;
static spinlock_t ch_list_lock;

static inline bool ch_has_mbo(struct comp_channel *c)
{
	return channel_has_mbo(c->iface, c->channel_id, &comp.cc) > 0;
}

static inline struct mbo *ch_get_mbo(struct comp_channel *c, struct mbo **mbo)
{
	if (!kfifo_peek(&c->fifo, mbo)) {
		*mbo = most_get_mbo(c->iface, c->channel_id, &comp.cc);
		if (*mbo)
			kfifo_in(&c->fifo, mbo, 1);
	}
	return *mbo;
}

static struct comp_channel *get_channel(struct most_interface *iface, int id)
{
	struct comp_channel *c, *tmp;
	unsigned long flags;

	spin_lock_irqsave(&ch_list_lock, flags);
	list_for_each_entry_safe(c, tmp, &channel_list, list) {
		if ((c->iface == iface) && (c->channel_id == id)) {
			spin_unlock_irqrestore(&ch_list_lock, flags);
			return c;
		}
	}
	spin_unlock_irqrestore(&ch_list_lock, flags);
	return NULL;
}

static void stop_channel(struct comp_channel *c)
{
	struct mbo *mbo;

	while (kfifo_out((struct kfifo *)&c->fifo, &mbo, 1))
		most_put_mbo(mbo);
	most_stop_channel(c->iface, c->channel_id, &comp.cc);
}

static void destroy_cdev(struct comp_channel *c)
{
	unsigned long flags;

	device_destroy(comp.class, c->devno);
	cdev_del(&c->cdev);
	spin_lock_irqsave(&ch_list_lock, flags);
	list_del(&c->list);
	spin_unlock_irqrestore(&ch_list_lock, flags);
}

static void destroy_channel(struct comp_channel *c)
{
	ida_simple_remove(&comp.minor_id, MINOR(c->devno));
	kfifo_free(&c->fifo);
	kfree(c);
}

/**
 * comp_open - implements the syscall to open the device
 * @inode: inode pointer
 * @filp: file pointer
 *
 * This stores the channel pointer in the private data field of
 * the file structure and activates the channel within the core.
 */
static int comp_open(struct inode *inode, struct file *filp)
{
	struct comp_channel *c;
	int ret;

	c = to_channel(inode->i_cdev);
	filp->private_data = c;

	if (((c->cfg->direction == MOST_CH_RX) &&
	     ((filp->f_flags & O_ACCMODE) != O_RDONLY)) ||
	     ((c->cfg->direction == MOST_CH_TX) &&
		((filp->f_flags & O_ACCMODE) != O_WRONLY))) {
		return -EACCES;
	}

	mutex_lock(&c->io_mutex);
	if (!c->dev) {
		mutex_unlock(&c->io_mutex);
		return -ENODEV;
	}

	if (c->access_ref) {
		mutex_unlock(&c->io_mutex);
		return -EBUSY;
	}

	c->mbo_offs = 0;
	ret = most_start_channel(c->iface, c->channel_id, &comp.cc);
	if (!ret)
		c->access_ref = 1;
	mutex_unlock(&c->io_mutex);
	return ret;
}

/**
 * comp_close - implements the syscall to close the device
 * @inode: inode pointer
 * @filp: file pointer
 *
 * This stops the channel within the core.
 */
static int comp_close(struct inode *inode, struct file *filp)
{
	struct comp_channel *c = to_channel(inode->i_cdev);

	mutex_lock(&c->io_mutex);
	spin_lock(&c->unlink);
	c->access_ref = 0;
	spin_unlock(&c->unlink);
	if (c->dev) {
		stop_channel(c);
		mutex_unlock(&c->io_mutex);
	} else {
		mutex_unlock(&c->io_mutex);
		destroy_channel(c);
	}
	return 0;
}

/**
 * comp_write - implements the syscall to write to the device
 * @filp: file pointer
 * @buf: pointer to user buffer
 * @count: number of bytes to write
 * @offset: offset from where to start writing
 */
static ssize_t comp_write(struct file *filp, const char __user *buf,
			  size_t count, loff_t *offset)
{
	int ret;
	size_t to_copy, left;
	struct mbo *mbo = NULL;
	struct comp_channel *c = filp->private_data;

	mutex_lock(&c->io_mutex);
	while (c->dev && !ch_get_mbo(c, &mbo)) {
		mutex_unlock(&c->io_mutex);

		if ((filp->f_flags & O_NONBLOCK))
			return -EAGAIN;
		if (wait_event_interruptible(c->wq, ch_has_mbo(c) || !c->dev))
			return -ERESTARTSYS;
		mutex_lock(&c->io_mutex);
	}

	if (unlikely(!c->dev)) {
		ret = -ENODEV;
		goto unlock;
	}

	to_copy = min(count, c->cfg->buffer_size - c->mbo_offs);
	left = copy_from_user(mbo->virt_address + c->mbo_offs, buf, to_copy);
	if (left == to_copy) {
		ret = -EFAULT;
		goto unlock;
	}

	c->mbo_offs += to_copy - left;
	if (c->mbo_offs >= c->cfg->buffer_size ||
	    c->cfg->data_type == MOST_CH_CONTROL ||
	    c->cfg->data_type == MOST_CH_ASYNC) {
		kfifo_skip(&c->fifo);
		mbo->buffer_length = c->mbo_offs;
		c->mbo_offs = 0;
		most_submit_mbo(mbo);
	}

	ret = to_copy - left;
unlock:
	mutex_unlock(&c->io_mutex);
	return ret;
}

/**
<