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Some devices have hardware buffers that can store a number of samples
for later consumption. Hardware usually provides interrupts to notify
the processor when the FIFO is full or when it has reached a certain
watermark level. This helps with reducing the number of interrupts to
the host processor and thus it helps decreasing the power consumption.
This patch enables usage of hardware FIFOs for IIO devices in
conjunction with software device buffers. When the hardware FIFO is
enabled the samples are stored in the hardware FIFO. The samples are
later flushed to the device software buffer when the number of entries
in the hardware FIFO reaches the hardware watermark or when a flush
operation is triggered by the user when doing a non-blocking read
on an empty software device buffer.
In order to implement hardware FIFO support the device drivers must
implement the following new operations: setting and getting the
hardware FIFO watermark level, flushing the hardware FIFO to the
software device buffer. The device must also expose information about
the hardware FIFO such it's minimum and maximum watermark and if
necessary a list of supported watermark values. Finally, the device
driver must activate the hardware FIFO when the device buffer is
enabled, if the current device settings allows it.
The software device buffer watermark is passed by the IIO core to the
device driver as a hint for the hardware FIFO watermark. The device
driver can adjust this value to allow for hardware limitations (such
as capping it to the maximum hardware watermark or adjust it to a
value that is supported by the hardware). It can also disable the
hardware watermark (and implicitly the hardware FIFO) it this value is
below the minimum hardware watermark.
Since a driver may support hardware FIFO only when not in triggered
buffer mode (due to different semantics of hardware FIFO sampling and
triggered sampling) this patch changes the IIO core code to allow
falling back to non-triggered buffered mode if no trigger is enabled.
Signed-off-by: Octavian Purdila <octavian.purdila@intel.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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Currently the IIO buffer blocking read only wait until at least one
data element is available.
This patch makes the reader sleep until enough data is collected before
returning to userspace. This should limit the read() calls count when
trying to get data in batches.
Co-author: Yannick Bedhomme <yannick.bedhomme@mobile-devices.fr>
Signed-off-by: Josselin Costanzi <josselin.costanzi@mobile-devices.fr>
[rebased and remove buffer timeout]
Signed-off-by: Octavian Purdila <octavian.purdila@intel.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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Move all core (non-custom) buffer attributes to a vector to make it
easier to add more of them in the future.
Signed-off-by: Octavian Purdila <octavian.purdila@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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There was a need for non triggered software buffer type. It can be used when
triggered model does not fit and INDIO_BUFFER_HARDWARE causes confusion because
the data stream can be obtained not directly form hardware backend.
Suggested-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Karol Wrona <k.wrona@samsung.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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Signed-off-by: Octavian Purdila <octavian.purdila@intel.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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We already do have the length field in the struct iio_buffer which is
expected to be in sync with the current size of the buffer. And currently
all implementations of the get_length callback either return this field or a
constant number.
This patch removes the get_length callback and replaces all occurrences in
the IIO core with directly accessing the length field of the buffer.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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If a buffer implementation does not implement the set_length() callback the
length will be static and can not be changed by userspace. Mark the length
attribute as a read only property in this case so userspace is aware of this
rather than just silently accepting any length value.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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All buffers want at least the length and the enable attribute. Move the
creation of those attributes to the core instead of having to do this in
each individual buffer implementation. This allows us to get rid of some
boiler-plate code.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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The next patch will introduce new dependencies in iio_buffer_alloc_sysfs()
to functions which are currently defined after iio_buffer_alloc_sysfs(). To
avoid forward declarations move both iio_buffer_alloc_sysfs() and
iio_buffer_free_sysfs() after those function.
This is split into two patches one moving the functions and one adding the
dependencies to make review of the actual changes easier.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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Originally device and buffer registration were kept as separate operations
in IIO to allow to register two distinct sets of channels for buffered and
non-buffered operations. This has since already been further restricted and
the channel set registered for the buffer needs to be a subset of the
channel set registered for the device. Additionally the possibility to not
have a raw (or processed) attribute for a channel which was registered for
the device was added a while ago. This means it is possible to not register
any device level attributes for a channel even if it is registered for the
device. Also if a channel's scan_index is set to -1 and the channel is
registered for the buffer it is ignored.
So in summary it means it is possible to register the same channel array for
both the device and the buffer yet still end up with distinctive sets of
channels for both of them. This makes the argument for having to have to
manually register the channels for both the device and the buffer invalid.
Considering that the vast majority of all drivers want to register the same
set of channels for both the buffer and the device it makes sense to move
the buffer registration into the core to avoid some boiler-plate code in the
device driver setup path.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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Individual drivers should not be messing with the scan mask that contains
the list of enabled channels. This is something that is supposed to be
managed by the core.
Now that the last few drivers that used it to configure a default scan mask
have been updated to not do this anymore we can unexport the function.
Note, this patch also requires moving a few functions around so they are all
declared before the first internal user.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Reviewed-by: Daniel Baluta <daniel.baluta@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio into work-next
Jonathan writes:
1st round of new IIO drivers, functionality and cleanups for the 3.18 cycle.
Maintainer Updates
* Add 3 designated reviewers for IIO. Lars, Peter and Hartmut have been
actively reviewing a lot of patches for a while now so this reflects
the status quo. These three are probably the only reason I keep
my head above the water!
New drivers and device support
* max5821 DAC
* Rockchip SARADC
* TI ADC128S052 ADC
* BMC150 Accelerometer
* exynos ADC driver gains support for s3c24xx and s3c64xx parts.
* kxcjk-1013 gainst range control and runtime PM support to drive
down it's power usage.
Driver removals
* Drop ad5930, ad99850, ad9852, ad9910 and ad9951 drivers on the simple
basis that they drivers just provided a register write function with
no compliant user space ABI whatsoever. Much better to drop them and
start again for these in the fullness of time.
Core Enhancements
* Join together neighbouring elements in the demux units that feeds
the binary interfaces. This cuts down on the number of individual
copies needed when splitting out individual channels from the incoming
channel scans.
* Other demux related cleanups such as using roundup instead of a local
implementation.
Cleanups
* Drop an unnecessary double setting of the owner field in xilinx adc.
* Some more patches to use managed (devm) interfaces to cut down on
complexity of removal code.
* adis16060 coding style fixlets.
* Fix some incorrect error returns in the Xilinx ADC driver.
* Coding style fixlets for various accelerometer drivers.
* Some sparse warning fixes to do with endianness and sign of variables.
* Fix an incorrect and entirely pointless use of sizeof on a dynamic pointer
in hid-sensor-magn-3d by dropping the relevant code.
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The size of the allocation is currently set to the size of the pointer
rather than the structure we should actually be allocating.
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Reported-by: kbuild@01.org
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
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git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging
Pull staging driver updates from Greg KH:
"Here's the big pull request for the staging driver tree for 3.17-rc1.
Lots of things in here, over 2000 patches, but the best part is this:
1480 files changed, 39070 insertions(+), 254659 deletions(-)
Thanks to the great work of Kristina Martšenko, 14 different staging
drivers have been removed from the tree as they were obsolete and no
one was willing to work on cleaning them up. Other than the driver
removals, loads of cleanups are in here (comedi, lustre, etc.) as well
as the usual IIO driver updates and additions.
All of this has been in the linux-next tree for a while"
* tag 'staging-3.17-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging: (2199 commits)
staging: comedi: addi_apci_1564: remove diagnostic interrupt support code
staging: comedi: addi_apci_1564: add subdevice to check diagnostic status
staging: wlan-ng: coding style problem fix
staging: wlan-ng: fixing coding style problems
staging: comedi: ii_pci20kc: request and ioremap memory
staging: lustre: bitwise vs logical typo
staging: dgnc: Remove unneeded dgnc_trace.c and dgnc_trace.h
staging: dgnc: rephrase comment
staging: comedi: ni_tio: remove some dead code
staging: rtl8723au: Fix static symbol sparse warning
staging: rtl8723au: usb_dvobj_init(): Remove unused variable 'pdev_desc'
staging: rtl8723au: Do not duplicate kernel provided USB macros
staging: rtl8723au: Remove never set struct pwrctrl_priv.bHWPowerdown
staging: rtl8723au: Remove two never set variables
staging: rtl8723au: RSSI_test is never set
staging:r8190: coding style: Fixed checkpatch reported Error
staging:r8180: coding style: Fixed too long lines
staging:r8180: coding style: Fixed commenting style
staging: lustre: ptlrpc: lproc_ptlrpc.c - fix dereferenceing user space buffer
staging: lustre: ldlm: ldlm_resource.c - fix dereferenceing user space buffer
...
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When copying multiple multiple samples that are adjacent in both the source as
well as the destination buffer, instead of creating a new demux table entry for
each sample just increase the length of the previous entry by the size of the
new sample. This makes the demuxing process slightly more efficient.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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Makes the code slightly shorter and a bit easier to understand.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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When creating the demux table we need to iterate over the selected scan mask for
the buffer to get the samples which should be copied to destination buffer.
Right now the code uses the mask which contains all active channels, which means
the demux table contains entries which causes it to copy all the samples from
source to destination buffer one by one without doing any demuxing.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Cc: Stable@vger.kernel.org
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Change sca3000_ring implementation so that it exports a data_available
function to iio.
Signed-off-by: Josselin Costanzi <josselin.costanzi@mobile-devices.fr>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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The current scan element type uses the following format:
[be|le]:[s|u]bits/storagebits[>>shift].
To specify multiple elements in this type, added a repeat value.
So new format is:
[be|le]:[s|u]bits/storagebitsXr[>>shift].
Here r is specifying how may times, real/storage bits are repeating.
When X is value is 0 or 1, then repeat value is not used in the format,
and it will be same as existing format.
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio into staging-linus
Jonathan writes:
First found of IIO fixes for the 3.15 cycle.
* Fix the platform data support for the at91 adc driver.
* A couple of related follow up patches get the support working again
for at91sam9260 and at91sam9g45 as the earlier patch results in a device
name change.
* A default timer value in the at91 adc driver was bonkers. Make it sane.
* Fix incorrect reporting of the integration time for the cm32181 light sensor
* Fix a missing break in the ad2s1200 driver which would have give a false
error return.
* Make sure buffer scan mask queries from userspace return 0/1 rather than
a fairly random value depending on their implementation of test_bit
* Fix leak of the i2c client and a null pointer dereference in the cm36651
driver.
* Fix a build warning on avr32 for the mxs-lradc (not exactly a critical
combination - but the issue was real).
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Ensure that querying the IIO buffer scan_mask returns a value of
0 or 1. Currently querying the scan mask has the value returned
by test_bit(), which returns either true or false. For some
architectures test_bit() may return -1 for true, which will appear
to return an error when returning from iio_scan_mask_query().
Additionally, it's important for the sysfs interface to consistently
return the same thing when querying the scan_mask.
Signed-off-by: Alec Berg <alecaberg@chromium.org>
Cc: stable@vger.kernel.org
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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Get rid of obsolete uses of goto error_ret and some empty lines.
Signed-off-by: Hartmut Knaack <knaack.h@gmx.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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Currently the IIO buffer interface only allows non-blocking reads. This patch
adds support for blocking IO. In blocking mode the thread will go to sleep if no
data is available and will wait for the buffer implementation to signal that new
data is available by waking up the buffers waitqueue.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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This patch adds a new data_available() callback to the iio_buffer_access_funcs
struct. The callback is used to indicate whether data is available in the buffer
for reading. It is meant to replace the stufftoread flag from the iio_buffer
struct. The reasoning for this is that the buffer implementation usually can
determine whether data is available rather easily based on its state, on the
other hand it can be rather tricky to update the stufftoread flag in a race free
way.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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We want these fixes in here as well.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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The functionality implemented by iio_sw_buffer_preenable() is now done directly
in the IIO core and previous users of iio_sw_buffer_preenable() have all been
updated to not use it anymore. It is unused now and can be remove.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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Currently a IIO device driver needs to make sure to update the buffer's bytes
per datum after the scan mask has changed. This is usually done in the preenable
callback by invoking iio_sw_buffer_preenable(). This is something that needs to
be done and is done for virtually all devices which support buffers (we
currently have only one exception). Also this a bit of a layering violation
since we have to call the buffer setup ops from the device setup ops. This
requires the device driver to know about the internal requirements of the buffer
(e.g. whether we need to call the set_bytes_per_datum) callback. And especially
with in-kernel buffer consumers, which allows to attach arbitrary buffers to a
device, this is something that the driver can't know.
Moving this to the core allows us to drop the individual calls to
iio_sw_buffer_preenable() from drivers.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Cc: Denis Ciocca <denis.ciocca@st.com>
Cc: Marek Vasut <marex@denx.de>
Cc: Zubair Lutfullah <zubair.lutfullah@gmail.com>
Cc: Jacek Anaszewski <j.anaszewski@samsung.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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Usually the active scan mask is freed in __iio_update_buffers() when the buffer
is disabled. But when the device is still sampling when it is removed we'll end
up disabling the buffers in iio_disable_all_buffers(). So we also need to free
the active scan mask here, otherwise it will be leaked.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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Since the kernel now disables all buffers when a device is unregistered it might
happen that a in-kernel consumer tries to disable that buffer again. So ignore
requests where the buffer already is in the desired state.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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We have the same code to free a IIO device attribute list in multiple place.
This patch adds a new helper function to take care of this and replaces the
custom instances with a call to the helper function. Note that we do not need to
call list_del() for each of the list items since we will never look at any of
the list items nor the list itself again.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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We need to make sure that in-kernel users of iio_update_buffers() do not race
against each other or against unregistration of the device. So we need to take
both the mlock and the info_exist_lock when calling iio_update_buffers() from a
in-kernel consumer.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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Once the device has been unregistered there won't be any new data no matter how
long a userspace application waits, so we might as well wake them up and let
them know.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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If the IIO device has been unregistered return -ENODEV for any further file
operations like read() and ioctl(). This avoids userspace being able to grab new
references to the device.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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Since the buffer is accessed by userspace we can not just free the buffers
memory once we are done with it in kernel space. There might still be open file
descriptors and userspace still might be accessing the buffer. This patch adds
support for reference counting to the IIO buffers. When a buffer is created and
initialized its initial reference count is set to 1. Instead of freeing the
memory of the buffer the buffer's _free() function will drop that reference
again. But only after the last reference to the buffer has been dropped the
buffer the buffer's memory will be freed. The IIO device will take a reference
to its primary buffer. The patch adds a small helper function for this called
iio_device_attach_buffer() which will get a reference to the buffer and assign
the buffer to the IIO device. This function must be used instead of assigning
the buffer to the device by hand. The reference is only dropped once the IIO
device is freed and we can be sure that there are no more open file handles. A
reference to a buffer will also be taken whenever the buffer is active to avoid
the buffer being freed while data is still being send to it.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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This resolves the merge problem with two iio drivers that Stephen
Rothwell pointed out.
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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Make sure to stop sampling when the device is removed, otherwise it will
continue to sample forever.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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if device has available_scan_masks set and the buffer is enabled without
any scan_elements enabled, in a NULL pointer is dereferenced in iio_compute_scan_bytes()
[ 18.993713] Unable to handle kernel NULL pointer dereference at virtual address 00000000
[ 19.002593] pgd = debd4000
[ 19.005432] [00000000] *pgd=9ebc0831, *pte=00000000, *ppte=00000000
[ 19.012329] Internal error: Oops: 17 [#1] PREEMPT ARM
[ 19.017639] Modules linked in:
[ 19.020843] CPU: 0 Not tainted (3.9.11-00036-g75c888a-dirty #207)
[ 19.027587] PC is at _find_first_bit_le+0xc/0x2c
[ 19.032440] LR is at iio_compute_scan_bytes+0x2c/0xf4
[ 19.037719] pc : [<c021dc60>] lr : [<c03198d0>] psr: 200d0013
[ 19.037719] sp : debd9ed0 ip : 00000000 fp : 000802bc
[ 19.049713] r10: 00000000 r9 : 00000000 r8 : deb67250
[ 19.055206] r7 : 00000000 r6 : 00000000 r5 : 00000000 r4 : deb67000
[ 19.062011] r3 : de96ec00 r2 : 00000000 r1 : 00000004 r0 : 00000000
[ 19.068847] Flags: nzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user
[ 19.076324] Control: 10c5387d Table: 9ebd4019 DAC: 00000015
problem is the rollback code in iio_update_buffers(), old_mask may be NULL (e.g. on first
call)
I'm not too confident about the fix; works for me...
Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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adding one return value check
fix one kerneldoc
Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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Change the type of the 'data' parameter for iio_push_to_buffers() from 'u8 *' to
'const void *'. Drivers typically use the correct type (e.g. __be16 *) for their
data buffer. When passing the buffer to iio_push_to_buffers() it needs to be
cast to 'u8 *' for the compiler to not complain (and also having to add __force
if we want to keep sparse happy as well). Since the buffer implementation should
not care about the data layout (except the size of one sample) using a void
pointer is the correct thing to do. Also make it const as the buffer
implementations are not supposed to modify it.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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Introduce an enum to specify whether the attribute is separate or
shared.
Factor out the bitmap handling for loop into a separate function.
Tidy up error handling and add a NULL assignment to squish a false
positive warning from GCC.
Change ext_info shared type from boolean to enum and update in all
drivers.
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
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We can skip having to loop through all the device's buffers to see if a certain
buffer is active, if we let the buffer's list head point to itself when the
buffer is inactive.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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1. make messages grepable (in one line)
2. include returned errno in them
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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Route all buffer writes through the demux.
Addition or removal of a buffer results in tear down and
setup of all the buffers for a given device.
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Tested-by: srinivas pandruvada <srinivas.pandruvada@intel.com>
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strict_strto* has been deprecated in favor of kstrto*. Use strict_strtouint
respective strict_strtoint, since that is what the functions we pass the
converted values to expect.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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Drop timestamp parameter from buffer store_to callback and subsequently from
iio_push_to_buffer. The timestamp parameter is unused and it seems likely that
it will stay unused in the future, so it should be safe to remove it.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio into staging-next
IIO: One new driver and a couple of nice cleanups.
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Add a helper function for validating a scan mask for devices where exactly one
channel must be selected during sampling. This is a common case among devices
which have scan mask restrictions so it makes sense to provide this function in
the core.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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This is useful for cases where the number of valid scan masks grows
exponentially, but it is rather easy to check whether a mask is valid or not
programmatically.
An example of such a case is a device with multiple ADCs where each ADC has a
upstream MUX, which allows to select from a number of physical channels.
+-------+ +-------+
| | | | --- Channel 1
| ADC 1 |---| MUX 1 | --- ...
| | | | --- Channel M
+-------+ +-------+
. . .
. . .
. . .
+-------+ +-------+
| | | | --- Channel M * N + 1
| ADC N |---| MUX N | --- ...
| | | | --- Channel M * N + M
+-------+ +-------+
The number of necessary scan masks for this case is (M+1)**N - 1, on the other
hand it is easy to check whether subsets for each ADC of the scanmask have only
one bit set.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
|
