linux-toradex.git/include/linux/counter.h, branch v5.19-rc8

counter: remove old and now unused registration API

2021-12-30T16:44:07+00:00

Usage of counter_register() yields issues in device lifetime tracking. All
drivers were converted to the new API, so the old one can go away.

Reviewed-by: Jonathan Cameron 
Acked-by: William Breathitt Gray 
Signed-off-by: Uwe Kleine-König 
Link: https://lore.kernel.org/r/20211230150300.72196-24-u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman

counter: Provide alternative counter registration functions

2021-12-30T16:44:06+00:00

The current implementation gets device lifetime tracking wrong. The
problem is that allocation of struct counter_device is controlled by the
individual drivers but this structure contains a struct device that
might have to live longer than a driver is bound. As a result a command
sequence like:

	{ sleep 5; echo bang; } > /dev/counter0 &
	sleep 1;
	echo 40000000.timer:counter > /sys/bus/platform/drivers/stm32-timer-counter/unbind

can keep a reference to the struct device and unbinding results in
freeing the memory occupied by this device resulting in an oops.

This commit provides two new functions (plus some helpers):
 - counter_alloc() to allocate a struct counter_device that is
   automatically freed once the embedded struct device is released
 - counter_add() to register such a device.

Note that this commit doesn't fix any issues, all drivers have to be
converted to these new functions to correct the lifetime problems.

Reviewed-by: Jonathan Cameron 
Signed-off-by: Uwe Kleine-König 
Link: https://lore.kernel.org/r/20211230150300.72196-14-u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman

counter: Provide a wrapper to access device private data

2021-12-30T16:44:06+00:00

For now this just wraps accessing struct counter_device::priv. However
this is about to change and converting drivers to this helper
individually makes fixing device lifetime issues result in easier to
review patches.

Reviewed-by: Jonathan Cameron 
Acked-by: William Breathitt Gray 
Signed-off-by: Uwe Kleine-König 
Link: https://lore.kernel.org/r/20211230150300.72196-5-u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman

counter: Add the necessary colons and indents to the comments of counter_compi

2021-12-21T09:32:08+00:00

Since commit aaec1a0f76ec ("counter: Internalize sysfs interface code")
introduce a warning as:

linux-next/Documentation/driver-api/generic-counter:234: ./include/linux/counter.h:43: WARNING: Unexpected indentation.
linux-next/Documentation/driver-api/generic-counter:234: ./include/linux/counter.h:45: WARNING: Block quote ends without a blank line; unexpected unindent.

Add the necessary colons and indents.

Fixes: aaec1a0f76ec ("counter: Internalize sysfs interface code")
Signed-off-by: Yanteng Si 
Signed-off-by: William Breathitt Gray 
Link: https://lore.kernel.org/r/26011e814d6eca02c7ebdbb92f171a49928a7e89.1640072891.git.vilhelm.gray@gmail.com
Signed-off-by: Greg Kroah-Hartman

counter: Fix use-after-free race condition for events_queue_size write

2021-10-21T11:02:47+00:00

A race condition is possible when writing to events_queue_size where the
events kfifo is freed during the execution of a kfifo_in(), resulting in
a use-after-free. This patch prevents such a scenario by protecting the
events queue in operation with a spinlock and locking before performing
the events queue size adjustment.

The existing events_lock mutex is renamed to events_out_lock to reflect
that it only protects events queue out operations. Because the events
queue in operations can occur in an interrupt context, a new
events_in_lock spinlock is introduced and utilized.

Fixes: feff17a550c7 ("counter: Implement events_queue_size sysfs attribute")
Cc: David Lechner 
Signed-off-by: William Breathitt Gray 
Link: https://lore.kernel.org/r/20211021103540.955639-1-vilhelm.gray@gmail.com
Signed-off-by: Greg Kroah-Hartman

counter: drop chrdev_lock

2021-10-19T09:36:28+00:00

This removes the chrdev_lock from the counter subsystem. This was
intended to prevent opening the chrdev more than once. However, this
doesn't work in practice since userspace can duplicate file descriptors
and pass file descriptors to other processes. Since this protection
can't be relied on, it is best to just remove it.

Suggested-by: Greg KH 
Acked-by: William Breathitt Gray 
Signed-off-by: David Lechner 
Link: https://lore.kernel.org/r/20211017185521.3468640-1-david@lechnology.com
Signed-off-by: Greg Kroah-Hartman

counter: Add character device interface

2021-10-17T09:53:52+00:00

This patch introduces a character device interface for the Counter
subsystem. Device data is exposed through standard character device read
operations. Device data is gathered when a Counter event is pushed by
the respective Counter device driver. Configuration is handled via ioctl
operations on the respective Counter character device node.

Cc: David Lechner 
Cc: Gwendal Grignou 
Cc: Dan Carpenter 
Cc: Oleksij Rempel 
Signed-off-by: William Breathitt Gray 
Link: https://lore.kernel.org/r/b8b8c64b4065aedff43699ad1f0e2f8d1419c15b.1632884256.git.vilhelm.gray@gmail.com
Signed-off-by: Jonathan Cameron

counter: Move counter enums to uapi header

2021-10-17T09:53:41+00:00

This is in preparation for a subsequent patch implementing a character
device interface for the Counter subsystem.

Reviewed-by: David Lechner 
Signed-off-by: William Breathitt Gray 
Link: https://lore.kernel.org/r/962a5f2027fafcf4f77c10e1baf520463960d1ee.1632884256.git.vilhelm.gray@gmail.com
Signed-off-by: Jonathan Cameron

counter: Update counter.h comments to reflect sysfs internalization

2021-10-17T09:53:11+00:00

The Counter subsystem architecture and driver implementations have
changed in order to handle Counter sysfs interactions in a more
consistent way. This patch updates the Generic Counter interface
header file comments to reflect the changes.

Signed-off-by: William Breathitt Gray 
Link: https://lore.kernel.org/r/19da8ae0c05381b0967c8a334b67f86b814eb880.1630031207.git.vilhelm.gray@gmail.com
Signed-off-by: Jonathan Cameron

counter: Internalize sysfs interface code

2021-10-17T09:52:58+00:00

This is a reimplementation of the Generic Counter driver interface.
There are no modifications to the Counter subsystem userspace interface,
so existing userspace applications should continue to run seamlessly.

The purpose of this patch is to internalize the sysfs interface code
among the various counter drivers into a shared module. Counter drivers
pass and take data natively (i.e. u8, u64, etc.) and the shared counter
module handles the translation between the sysfs interface and the
device drivers. This guarantees a standard userspace interface for all
counter drivers, and helps generalize the Generic Counter driver ABI in
order to support the Generic Counter chrdev interface (introduced in a
subsequent patch) without significant changes to the existing counter
drivers.

Note, Counter device registration is the same as before: drivers
populate a struct counter_device with components and callbacks, then
pass the structure to the devm_counter_register function. However,
what's different now is how the Counter subsystem code handles this
registration internally.

Whereas before callbacks would interact directly with sysfs data, this
interaction is now abstracted and instead callbacks interact with native
C data types. The counter_comp structure forms the basis for Counter
extensions.

The counter-sysfs.c file contains the code to parse through the
counter_device structure and register the requested components and
extensions. Attributes are created and populated based on type, with
respective translation functions to handle the mapping between sysfs and
the counter driver callbacks.

The translation performed for each attribute is straightforward: the
attribute type and data is parsed from the counter_attribute structure,
the respective counter driver read/write callback is called, and sysfs
I/O is handled before or after the driver read/write function is called.

Cc: Jarkko Nikula 
Cc: Patrick Havelange 
Cc: Kamel Bouhara 
Cc: Maxime Coquelin 
Cc: Alexandre Torgue 
Cc: Dan Carpenter 
Acked-by: Syed Nayyar Waris 
Reviewed-by: David Lechner 
Tested-by: David Lechner 
Signed-off-by: William Breathitt Gray 
Reviewed-by: Fabrice Gasnier  # for stm32
Link: https://lore.kernel.org/r/c68b4a1ffb195c1a2f65e8dd5ad7b7c14e79c6ef.1630031207.git.vilhelm.gray@gmail.com
Signed-off-by: Jonathan Cameron