iio: core: move 'mlock' to 'struct iio_dev_opaque'

Now that there are no more users accessing 'mlock' directly, we can move
it to the iio_dev private structure. Hence, it's now explicit that new
driver's should not directly use this lock.

Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20221012151620.1725215-5-nuno.sa@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: Use per-device lockdep class for mlock

If an IIO driver uses callbacks from another IIO driver and calls
iio_channel_start_all_cb() from one of its buffer setup ops, then
lockdep complains due to the lock nesting, as in the below example with
lmp91000.

Since the locks are being taken on different IIO devices, there is no
actual deadlock. Fix the warning by telling lockdep to use a different
class for each iio_device.

============================================
WARNING: possible recursive locking detected
--------------------------------------------
python3/23 is trying to acquire lock:
(&indio_dev->mlock){+.+.}-{3:3}, at: iio_update_buffers

but task is already holding lock:
(&indio_dev->mlock){+.+.}-{3:3}, at: enable_store

other info that might help us debug this:
Possible unsafe locking scenario:

CPU0
----
lock(&indio_dev->mlock);
lock(&indio_dev->mlock);

*** DEADLOCK ***

May be due to missing lock nesting notation

5 locks held by python3/23:
#0: (sb_writers#5){.+.+}-{0:0}, at: ksys_write
#1: (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter
#2: (kn->active#14){.+.+}-{0:0}, at: kernfs_fop_write_iter
#3: (&indio_dev->mlock){+.+.}-{3:3}, at: enable_store
#4: (&iio_dev_opaque->info_exist_lock){+.+.}-{3:3}, at: iio_update_buffers

Call Trace:
__mutex_lock
iio_update_buffers
iio_channel_start_all_cb
lmp91000_buffer_postenable
__iio_update_buffers
enable_store

Fixes: 67e17300dc1d76 ("iio: potentiostat: add LMP91000 support")
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220829091840.2791846-1-vincent.whitchurch@axis.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: core: Move the currentmode entry to the opaque structure

This entry should, under no situation, be modified by device
drivers. Now that we have limited its read access to device drivers
really needing it and did so through a dedicated helper, we can
easily move this variable to the opaque structure in order to
prevent any further modification from non-authorized code (out of the
core, basically).

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Link: https://lore.kernel.org/r/20220207143840.707510-12-miquel.raynal@bootlin.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: core: Introduce iio_push_to_buffers_with_ts_unaligned()

Whilst it is almost always possible to arrange for scan data to be
read directly into a buffer that is suitable for passing to
iio_push_to_buffers_with_timestamp(), there are a few places where
leading data needs to be skipped over.

For these cases introduce a function that will allocate an appropriate
sized and aligned bounce buffer (if not already allocated) and copy
the unaligned data into that before calling
iio_push_to_buffers_with_timestamp() on the bounce buffer.
We tie the lifespace of this buffer to that of the iio_dev.dev
which should ensure no memory leaks occur.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20210613151039.569883-2-jic23@kernel.org

iio: core: move @clock_id from struct iio_dev to struct iio_dev_opaque

There is already an acessor function used to access it, making this
move straight forward.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Link: https://lore.kernel.org/r/20210426174911.397061-10-jic23@kernel.org

iio: core: move @flags from struct iio_dev to struct iio_dev_opaque

No reason any driver should ever need access to this field, so hide it.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Link: https://lore.kernel.org/r/20210426174911.397061-9-jic23@kernel.org

iio: core: move @chrdev from struct iio_dev to struct iio_dev_opaque

No reason for this to be exposed to the drivers, so lets move it to the
opaque structure.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Link: https://lore.kernel.org/r/20210426174911.397061-8-jic23@kernel.org

iio: core: move @info_exist_lock to struct iio_dev_opaque

This lock is only of interest to the IIO core, so make it only
visible there.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Link: https://lore.kernel.org/r/20210426174911.397061-7-jic23@kernel.org

iio: core: move @scan_index_timestamp to struct iio_dev_opaque

No reason for this cached value to be exposed to drivers so move it
to the opaque structure.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Link: https://lore.kernel.org/r/20210426174911.397061-6-jic23@kernel.org

iio: core: move @trig_readonly from struct iio_dev to struct iio_dev_opaque

This is only set via the iio_trig_set_immutable() call and later used
by the IIO core so there is no benefit in drivers being able to access
it.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Link: https://lore.kernel.org/r/20210426174911.397061-5-jic23@kernel.org

iio: core: move @driver_module from struct iio_dev to struct iio_dev_opaque

Continuing move to hide internal elements from drivers, move this structure
element over. It's only accessed from iio core files so this one was
straight forward and no accessor functions are needed.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Link: https://lore.kernel.org/r/20210426174911.397061-4-jic23@kernel.org

iio: avoid shadowing of variable name in to_iio_dev_opaque()

indio_dev was both the macro input parameter and the field name
in this macro. That causes trouble if the instance of
struct iio_dev passed in is not called indio_dev.

Whilst a fix of sorts, no need to backport as it seems we never
hit this previously due to some very consistent naming in IIO.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Link: https://lore.kernel.org/r/20210426174911.397061-3-jic23@kernel.org

iio: core: move @id from struct iio_dev to struct iio_dev_opaque

Continuing from Alexandru Ardelean's introduction of the split between
driver modifiable fields and those that should only be set by the core.

This could have been done in two steps to make the actual move after
introducing iio_device_id() but there seemed limited point to that
given how mechanical the majority of the patch is.

Includes fixup from Alex for missing mxs-lradc-adc conversion.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Link: https://lore.kernel.org/r/20210426174911.397061-2-jic23@kernel.org

iio: buffer: add ioctl() to support opening extra buffers for IIO device

With this change, an ioctl() call is added to open a character device for a
buffer. The ioctl() number is 'i' 0x91, which follows the
IIO_GET_EVENT_FD_IOCTL ioctl.

The ioctl() will return an FD for the requested buffer index. The indexes
are the same from the /sys/iio/devices/iio:deviceX/bufferY (i.e. the Y
variable).

Since there doesn't seem to be a sane way to return the FD for buffer0 to
be the same FD for the /dev/iio:deviceX, this ioctl() will return another
FD for buffer0 (or the first buffer). This duplicate FD will be able to
access the same buffer object (for buffer0) as accessing directly the
/dev/iio:deviceX chardev.

Also, there is no IIO_BUFFER_GET_BUFFER_COUNT ioctl() implemented, as the
index for each buffer (and the count) can be deduced from the
'/sys/bus/iio/devices/iio:deviceX/bufferY' folders (i.e the number of
bufferY folders).

Used following C code to test this:
-------------------------------------------------------------------

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <fcntl.h"
#include <errno.h>

#define IIO_BUFFER_GET_FD_IOCTL _IOWR('i', 0x91, int)

int main(int argc, char *argv[])
{
int fd;
int fd1;
int ret;

if ((fd = open("/dev/iio:device0", O_RDWR))<0) {
fprintf(stderr, "Error open() %d errno %d\n",fd, errno);
return -1;
}

fprintf(stderr, "Using FD %d\n", fd);

fd1 = atoi(argv[1]);

ret = ioctl(fd, IIO_BUFFER_GET_FD_IOCTL, &fd1);
if (ret < 0) {
fprintf(stderr, "Error for buffer %d ioctl() %d errno %d\n", fd1, ret, errno);
close(fd);
return -1;
}

fprintf(stderr, "Got FD %d\n", fd1);

close(fd1);
close(fd);

return 0;
}
-------------------------------------------------------------------

Results are:
-------------------------------------------------------------------
# ./test 0
Using FD 3
Got FD 4

# ./test 1
Using FD 3
Got FD 4

# ./test 2
Using FD 3
Got FD 4

# ./test 3
Using FD 3
Got FD 4

# ls /sys/bus/iio/devices/iio\:device0
buffer buffer0 buffer1 buffer2 buffer3 dev
in_voltage_sampling_frequency in_voltage_scale
in_voltage_scale_available
name of_node power scan_elements subsystem uevent
-------------------------------------------------------------------

iio:device0 has some fake kfifo buffers attached to an IIO device.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20210215104043.91251-21-alexandru.ardelean@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: buffer: introduce support for attaching more IIO buffers

With this change, calling iio_device_attach_buffer() will actually attach
more buffers.
Right now this doesn't do any validation of whether a buffer is attached
twice; maybe that can be added later (if needed). Attaching a buffer more
than once should yield noticeably bad results.

The first buffer is the legacy buffer, so a reference is kept to it.

At this point, accessing the data for the extra buffers (that are added
after the first one) isn't possible yet.

The iio_device_attach_buffer() is also changed to return an error code,
which for now is -ENOMEM if the array could not be realloc-ed for more
buffers.
To adapt to this new change iio_device_attach_buffer() is called last in
all place where it's called. The realloc failure is a bit difficult to
handle during un-managed calls when unwinding, so it's better to have this
as the last error in the setup_buffer calls.

At this point, no driver should call iio_device_attach_buffer() directly,
it should call one of the {devm_}iio_triggered_buffer_setup() or
devm_iio_kfifo_buffer_setup() or devm_iio_dmaengine_buffer_setup()
functions. This makes iio_device_attach_buffer() a bit easier to handle.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20210215104043.91251-20-alexandru.ardelean@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: core: merge buffer/ & scan_elements/ attributes

With this change, we create a new directory for the IIO device called
buffer0, under which both the old buffer/ and scan_elements/ are stored.

This is done to simplify the addition of multiple IIO buffers per IIO
device. Otherwise we would need to add a bufferX/ and scan_elementsX/
directory for each IIO buffer.
With the current way of storing attribute groups, we can't have directories
stored under each other (i.e. scan_elements/ under buffer/), so the best
approach moving forward is to merge their attributes.

The old/legacy buffer/ & scan_elements/ groups are not stored on the opaque
IIO device object. This way the IIO buffer can have just a single
attribute_group object, saving a bit of memory when adding multiple IIO
buffers.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20210215104043.91251-13-alexandru.ardelean@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: core: rework iio device group creation

Up until now, the device groups that an IIO device had were limited to 6.
Two of these groups would account for buffer attributes (the buffer/ and
scan_elements/ directories).

Since we want to add multiple buffers per IIO device, this number may not
be enough, when adding a second buffer. So, this change reallocates the
groups array whenever an IIO device group is added, via a
iio_device_register_sysfs_group() helper.

This also means that the groups array should be assigned to
'indio_dev.dev.groups' really late, right before {cdev_}device_add() is
called to do the entire setup.
And we also must take care to free this array when the sysfs resources are
being cleaned up.

With this change we can also move the 'groups' & 'groupcounter' fields to
the iio_dev_opaque object. Up until now, this didn't make a whole lot of
sense (especially since we weren't sure how multibuffer support would look
like in the end).
But doing it now kills one birds with one stone.

An alternative, would be to add a configurable Kconfig symbol
CONFIG_IIO_MAX_BUFFERS_PER_DEVICE (or something like that) and compute a
static maximum of the groups we can support per IIO device. But that would
probably annoy a few people since that would make the system less
configurable.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20210215104043.91251-11-alexandru.ardelean@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: core: centralize ioctl() calls to the main chardev

The aim of this is to improve a bit the organization of ioctl() calls in
IIO core. Currently the chardev is split across IIO core sub-modules/files.
The main chardev has to be able to handle ioctl() calls, and if we need to
add buffer ioctl() calls, this would complicate things.

The 'industrialio-core.c' file will provide a 'iio_device_ioctl()' which
will iterate over a list of ioctls registered with the IIO device. These
can be event ioctl() or buffer ioctl() calls, or something else.

Each ioctl() handler will have to return a IIO_IOCTL_UNHANDLED code (which
is positive 1), if the ioctl() did not handle the call in any. This
eliminates any potential ambiguities about negative error codes, which
should fail the call altogether.

If any ioctl() returns 0, it was considered that it was serviced
successfully and the loop will exit.

This change also moves the handling of the IIO_GET_EVENT_FD_IOCTL command
inside 'industrialio-event.c', where this is better suited.

This patch is a combination of 2 other patches from an older series:
Patch 1: iio: core: add simple centralized mechanism for ioctl() handlers
Link: https://lore.kernel.org/linux-iio/20200427131100.50845-6-alexandru.ardelean@analog.com/
Patch 2: iio: core: use new common ioctl() mechanism
Link: https://lore.kernel.org/linux-iio/20200427131100.50845-7-alexandru.ardelean@analog.com/

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20200924084155.99406-1-alexandru.ardelean@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: core: move event interface on the opaque struct

Same as with other private fields, this moves the event interface reference
to the opaque IIO device object, to be invisible to drivers.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: core: move iio_dev's buffer_list to the private iio device object

This change moves the 'buffer_list' away from the public IIO device object
into the private part.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: core: move channel list & group to private iio device object

This change bit straightforward and simple, since the
'channel_attr_list' & 'chan_attr_group' fields are only used in
'industrialio-core.c'.

This change moves to the private IIO device object

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: core: move debugfs data on the private iio dev info

This change moves all iio_dev debugfs fields to the iio_dev_priv object.
It's not the biggest advantage yet (to the whole thing of abstractization)
but it's a start.

The iio_get_debugfs_dentry() function (which is moved in
industrialio-core.c) needs to also be guarded against the CONFIG_DEBUG_FS
symbol, when it isn't defined. We do want to keep the inline definition in
the iio.h header, so that the compiler can better infer when to compile out
debugfs code that is related to the IIO debugfs directory.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: core: wrap IIO device into an iio_dev_opaque object

There are plenty of bad designs we want to discourage or not have to review
manually usually about accessing private (marked as [INTERN]) fields of
'struct iio_dev'.

Sometimes users copy drivers that are not always the best examples.

A better idea is to hide those fields into the framework.
For 'struct iio_dev' this is a 'struct iio_dev_opaque' which wraps a public
'struct iio_dev' object.

In the next series, some fields will be moved to this new struct, each with
it's own rework.

This rework will not be complete-able for a while, as many fields need some
drivers to be reworked in order to finalize them (e.g. 'indio_dev->mlock').

But some fields can already be moved, and in time, all of them may get
there (in the 'struct iio_dev_opaque' object).

Since a lot of drivers also call 'iio_priv()', in order to preserve
fast-paths (where this matters), the public iio_dev object will have a
'priv' field that will have the pointer to the private information already
computed. The reference returned by this field should be guaranteed to be
cacheline aligned.

The opaque parts will be moved into the 'include/linux/iio/iio-opaque.h'
header. Should the hidden information be required for some debugging or
some special needs, it can be made available via this header.
Otherwise, only the IIO core files should include this file.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>