Contribution to linux-iio for GSOC 2021

Contribution to linux-iio for GSOC 2021

[Utkarsh Verma]

Hello,

This is Utkarsh Verma. I am a 3rd year Bachelor of Technology
Undergrad in Electronics Engineering from HBTU, Kanpur, India.

I want to participate in GSOC this summer, by contributing to the IIO
subsystem. But more importantly, I want to be a part of this community
and get my hands dirty.

I have done the operating system course and know the very basics of
Linux Kernel. I have also read some chapters of the "Linux Device
Drivers" book. I am very new to the iio subsystem and I am still
reading the documentation and the conversation on the mailing list. So
if anyone can suggest some easy fixes/tasks for getting started would
really be appreciated.

I would be really happy to contribute.

Regards,
Utkarsh Verma

Re: Contribution to linux-iio for GSOC 2021

[Jonathan Cameron]

On Wed, 10 Mar 2021 19:24:39 +0530
Utkarsh Verma <utkarshverma294@gmail.com> wrote:

> Hello,
> 
> This is Utkarsh Verma. I am a 3rd year Bachelor of Technology
> Undergrad in Electronics Engineering from HBTU, Kanpur, India.
> 
> I want to participate in GSOC this summer, by contributing to the IIO
> subsystem. But more importantly, I want to be a part of this community
> and get my hands dirty.
> 
> I have done the operating system course and know the very basics of
> Linux Kernel. I have also read some chapters of the "Linux Device
> Drivers" book. I am very new to the iio subsystem and I am still
> reading the documentation and the conversation on the mailing list. So
> if anyone can suggest some easy fixes/tasks for getting started would
> really be appreciated.
> 
> I would be really happy to contribute.
> 
> Regards,
> Utkarsh Verma

Hi Utkarsh,

Welcome to IIO.

If you want a practical immediate task to make sure you have flow
of submitting patches etc correct, one issue we've just started seeing
is that when we do

make W=1

we get some misleading reports like:

> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git testing
> head:   4ef57c4862e38e6034978d8b247a511292d7055a
> commit: 1cabd1c21b2a6c5b0dd3fdcffe0b24c1d0e4fc38 [72/74] iio: hrtimer: Allow sub Hz granularity
> config: x86_64-randconfig-a011-20210308 (attached as .config)
> compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 3a11a41795bec548e91621caaa4cc00fc31b2212)
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # install x86_64 cross compiling tool for clang build
>         # apt-get install binutils-x86-64-linux-gnu
>         # https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/commit/?id=1cabd1c21b2a6c5b0dd3fdcffe0b24c1d0e4fc38
>         git remote add iio https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git
>         git fetch --no-tags iio testing
>         git checkout 1cabd1c21b2a6c5b0dd3fdcffe0b24c1d0e4fc38
>         # save the attached .config to linux build tree
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
>
> All warnings (new ones prefixed by >>):
>  
> >> drivers/iio/trigger/iio-trig-hrtimer.c:20: warning: expecting prototype for O periodic hrtimer trigger driver(). Prototype was for PSEC_PER_SEC() instead  
>
>
> vim +20 drivers/iio/trigger/iio-trig-hrtimer.c
>
>     18
>     19  /* Defined locally, not in time64.h yet. */  
>   > 20  #define PSEC_PER_SEC   1000000000000LL  
>     21
>

Gwendal figured out what was going on.  It's down to an incorrect marking of the
initial comment block (where copyright notice etc is ) as kernel doc
by prefixing it with /**

If you'd like to first fine one of those cases and send a patch fixing it that
would be great.  Once we've sanity checked that first one for process issues etc
you could then ensure there are no other instances in IIO.

No problem if not and you want something more substantial to start with.
This is just something that hit my inbox today that I'd otherwise clean up,
but seemed like a good task for anyone wanting to get started!

Thanks,

Jonathan

Re: Contribution to linux-iio for GSOC 2021

[Jonathan Cameron]

On Wed, 10 Mar 2021 17:45:35 +0000
Jonathan Cameron <Jonathan.Cameron@Huawei.com> wrote:

> On Wed, 10 Mar 2021 19:24:39 +0530
> Utkarsh Verma <utkarshverma294@gmail.com> wrote:
> 
> > Hello,
> > 
> > This is Utkarsh Verma. I am a 3rd year Bachelor of Technology
> > Undergrad in Electronics Engineering from HBTU, Kanpur, India.
> > 
> > I want to participate in GSOC this summer, by contributing to the IIO
> > subsystem. But more importantly, I want to be a part of this community
> > and get my hands dirty.
> > 
> > I have done the operating system course and know the very basics of
> > Linux Kernel. I have also read some chapters of the "Linux Device
> > Drivers" book. I am very new to the iio subsystem and I am still
> > reading the documentation and the conversation on the mailing list. So
> > if anyone can suggest some easy fixes/tasks for getting started would
> > really be appreciated.
> > 
> > I would be really happy to contribute.
> > 
> > Regards,
> > Utkarsh Verma  
> 
> Hi Utkarsh,
> 
> Welcome to IIO.
> 
> If you want a practical immediate task to make sure you have flow
> of submitting patches etc correct, one issue we've just started seeing
> is that when we do
> 
> make W=1
> 
> we get some misleading reports like:
> 
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git testing
> > head:   4ef57c4862e38e6034978d8b247a511292d7055a
> > commit: 1cabd1c21b2a6c5b0dd3fdcffe0b24c1d0e4fc38 [72/74] iio: hrtimer: Allow sub Hz granularity
> > config: x86_64-randconfig-a011-20210308 (attached as .config)
> > compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 3a11a41795bec548e91621caaa4cc00fc31b2212)
> > reproduce (this is a W=1 build):
> >         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> >         chmod +x ~/bin/make.cross
> >         # install x86_64 cross compiling tool for clang build
> >         # apt-get install binutils-x86-64-linux-gnu
> >         # https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/commit/?id=1cabd1c21b2a6c5b0dd3fdcffe0b24c1d0e4fc38
> >         git remote add iio https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git
> >         git fetch --no-tags iio testing
> >         git checkout 1cabd1c21b2a6c5b0dd3fdcffe0b24c1d0e4fc38
> >         # save the attached .config to linux build tree
> >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64
> >
> > If you fix the issue, kindly add following tag as appropriate
> > Reported-by: kernel test robot <lkp@intel.com>
> >
> > All warnings (new ones prefixed by >>):
> >    
> > >> drivers/iio/trigger/iio-trig-hrtimer.c:20: warning: expecting prototype for O periodic hrtimer trigger driver(). Prototype was for PSEC_PER_SEC() instead    
> >
> >
> > vim +20 drivers/iio/trigger/iio-trig-hrtimer.c
> >
> >     18
> >     19  /* Defined locally, not in time64.h yet. */    
> >   > 20  #define PSEC_PER_SEC   1000000000000LL    
> >     21
> >  
> 
> Gwendal figured out what was going on.  It's down to an incorrect marking of the
> initial comment block (where copyright notice etc is ) as kernel doc
> by prefixing it with /**
> 
> If you'd like to first fine one of those cases and send a patch fixing it that
> would be great.  Once we've sanity checked that first one for process issues etc
> you could then ensure there are no other instances in IIO.
> 
> No problem if not and you want something more substantial to start with.
> This is just something that hit my inbox today that I'd otherwise clean up,
> but seemed like a good task for anyone wanting to get started!

Actually scrap that idea.  Serves me right for not reading all my IIO related emails
but Gwendal already sent out a patch fixing them all.  Sorry!

Jonathan

> 
> Thanks,
> 
> Jonathan

Re: Contribution to linux-iio for GSOC 2021

[Alexandru Ardelean]

On Wed, Mar 10, 2021 at 8:20 PM Jonathan Cameron
<Jonathan.Cameron@huawei.com> wrote:
>
> On Wed, 10 Mar 2021 17:45:35 +0000
> Jonathan Cameron <Jonathan.Cameron@Huawei.com> wrote:
>
> > On Wed, 10 Mar 2021 19:24:39 +0530
> > Utkarsh Verma <utkarshverma294@gmail.com> wrote:
> >
> > > Hello,
> > >
> > > This is Utkarsh Verma. I am a 3rd year Bachelor of Technology
> > > Undergrad in Electronics Engineering from HBTU, Kanpur, India.
> > >
> > > I want to participate in GSOC this summer, by contributing to the IIO
> > > subsystem. But more importantly, I want to be a part of this community
> > > and get my hands dirty.
> > >
> > > I have done the operating system course and know the very basics of
> > > Linux Kernel. I have also read some chapters of the "Linux Device
> > > Drivers" book. I am very new to the iio subsystem and I am still
> > > reading the documentation and the conversation on the mailing list. So
> > > if anyone can suggest some easy fixes/tasks for getting started would
> > > really be appreciated.
> > >
> > > I would be really happy to contribute.

One thing I've always wanted to do, is to convert the entire IIO
subsystem to devm_ variants.
Essentially getting rid of the iio_device_unregister() function in
favor of using devm_iio_device_unregister() and similar.

There's about ~217 uses of this function.
The more complicated one is in the 'drivers/platform/x86/toshiba_acpi.c'
I think reworking the Toshiba ACPI driver would also be interesting,
but it is some work.

Now, converting everything to devm_ variants can be considered a bit
of an obsession [by some people].
But I sometimes find potential memory leaks by doing this conversion.
And chances are that we may never be able to fully convert the IIO API
to be devm_ variant-only.
But it is an interesting process [for me], just the cleanup itself.

Another one, that was interesting until 1-2 years ago, was the
conversion of OF drivers to be a bit more ACPI friendly [as well].
This is also a bit of work to convert drivers that use only
of_property_read_xxxx()  functions to   device_property_read_xxx()
functions.
This isn't always straightforward in all drivers, but I do find it
interesting to unify the OF & ACPI interfaces, so that all you have to
do, is just switch the system from OF to ACPI underneath, and if the
device-tree conversion to ACPI is done right, it just works.

Then, there's the matter of moving fields [marked as [INTERN] )  from
"struct iio_dev"  to "struct iio_dev_opaque".
The value of this conversion is to reduce the review pain of having to
tell people not-to-use [INTERN] fields [especially when older drivers
do].

> > >
> > > Regards,
> > > Utkarsh Verma
> >
> > Hi Utkarsh,
> >
> > Welcome to IIO.
> >
> > If you want a practical immediate task to make sure you have flow
> > of submitting patches etc correct, one issue we've just started seeing
> > is that when we do
> >
> > make W=1
> >
> > we get some misleading reports like:
> >
> > > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git testing
> > > head:   4ef57c4862e38e6034978d8b247a511292d7055a
> > > commit: 1cabd1c21b2a6c5b0dd3fdcffe0b24c1d0e4fc38 [72/74] iio: hrtimer: Allow sub Hz granularity
> > > config: x86_64-randconfig-a011-20210308 (attached as .config)
> > > compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 3a11a41795bec548e91621caaa4cc00fc31b2212)
> > > reproduce (this is a W=1 build):
> > >         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> > >         chmod +x ~/bin/make.cross
> > >         # install x86_64 cross compiling tool for clang build
> > >         # apt-get install binutils-x86-64-linux-gnu
> > >         # https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/commit/?id=1cabd1c21b2a6c5b0dd3fdcffe0b24c1d0e4fc38
> > >         git remote add iio https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git
> > >         git fetch --no-tags iio testing
> > >         git checkout 1cabd1c21b2a6c5b0dd3fdcffe0b24c1d0e4fc38
> > >         # save the attached .config to linux build tree
> > >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64
> > >
> > > If you fix the issue, kindly add following tag as appropriate
> > > Reported-by: kernel test robot <lkp@intel.com>
> > >
> > > All warnings (new ones prefixed by >>):
> > >
> > > >> drivers/iio/trigger/iio-trig-hrtimer.c:20: warning: expecting prototype for O periodic hrtimer trigger driver(). Prototype was for PSEC_PER_SEC() instead
> > >
> > >
> > > vim +20 drivers/iio/trigger/iio-trig-hrtimer.c
> > >
> > >     18
> > >     19  /* Defined locally, not in time64.h yet. */
> > >   > 20  #define PSEC_PER_SEC   1000000000000LL
> > >     21
> > >
> >
> > Gwendal figured out what was going on.  It's down to an incorrect marking of the
> > initial comment block (where copyright notice etc is ) as kernel doc
> > by prefixing it with /**
> >
> > If you'd like to first fine one of those cases and send a patch fixing it that
> > would be great.  Once we've sanity checked that first one for process issues etc
> > you could then ensure there are no other instances in IIO.
> >
> > No problem if not and you want something more substantial to start with.
> > This is just something that hit my inbox today that I'd otherwise clean up,
> > but seemed like a good task for anyone wanting to get started!
>
> Actually scrap that idea.  Serves me right for not reading all my IIO related emails
> but Gwendal already sent out a patch fixing them all.  Sorry!
>
> Jonathan
>
> >
> > Thanks,
> >
> > Jonathan
>