[GSoC] AD7292 driver project

[GSoC] AD7292 driver project

[Karuna Grewal]

Hello,

I'm interested in working on the AD7292 driver for Linux kernel as a
part of the GSoC project. I've previous experience working with device
drivers and am also familiar with couple of Linux kernel's subsystems.
For a starting point I wonder if someone can point out some tasks
which I could work upon as the project page doesn't elaborate much
about it.
In case the idea is to start working on the driver itself I'd like to
discuss about the same.

Best Regards,
Karuna Grewal

Re: [GSoC] AD7292 driver project

[Jonathan Cameron]

On Sat, 16 Mar 2019 16:09:36 +0530
Karuna Grewal <karunagrewal98@gmail.com> wrote:

> Hello,
> 
> I'm interested in working on the AD7292 driver for Linux kernel as a
> part of the GSoC project. I've previous experience working with device
> drivers and am also familiar with couple of Linux kernel's subsystems.
> For a starting point I wonder if someone can point out some tasks
> which I could work upon as the project page doesn't elaborate much
> about it.
> In case the idea is to start working on the driver itself I'd like to
> discuss about the same.
> 
> Best Regards,
> Karuna Grewal

Hi Karuna and welcome to IIO.

I have nothing (directly) to do with the GSOC projects, but I'm always
happy to suggest tasks to anyone ;)

Obviously I don't know how 'in depth' you would like, but a couple
of immediate thoughts come to mind.

We have been trying to remove all direct use of the mlock mutex
in struct iio_dev from drivers.  It has one very specific and tightly
defined purpose to protect drivers from trying to do things they
shouldn't when changing from a polled mode to one which is interrupt
driven (DIRECT to BUFFERED).  Unfortunately we weren't great at
enforcing the distinction in the early days of IIO.

The solution is almost always to replace the use of mlock with
either calls to iio_claim_direct_mode (if it is an open coded
version of what the mlock is intended for) or to introduce a
lock within the driver itself with well defined scope covering
whatever mlock was incorrectly being used for.

Another traditional area for people first getting involved in IIO is
to look at the drivers that are still in drivers/staging/iio
but to be honest there are not many left there now so that isn't
as fruitful as it used to be.  If you do want to look at those, do
send a message to the list to confirm no one else is currently
looking a the same driver.

Also very useful if you are going to be looking at IIO drivers is
to get yourself setup with a suitable test board and any random
cheap sensor (dx.com and similar are very cheap if rather slow).

That way you will have verified your buses and similar before
trying to start work on a new sensor.  Far too much time gets wasted
trying to get a device to talk, just to discover something is wrong
in the platform setup and nothing is going out on the wires.

If you want more suggestions, feel free to ask.

Jonathan

Re: [GSoC] AD7292 driver project

[Karuna Grewal]

Apologies for the delayed response.

On Sun, Mar 17, 2019 at 12:43 AM Jonathan Cameron
<jic23@jic23.retrosnub.co.uk> wrote:
> We have been trying to remove all direct use of the mlock mutex
> in struct iio_dev from drivers.  It has one very specific and tightly
> defined purpose to protect drivers from trying to do things they
> shouldn't when changing from a polled mode to one which is interrupt
> driven (DIRECT to BUFFERED).  Unfortunately we weren't great at
> enforcing the distinction in the early days of IIO.

> The solution is almost always to replace the use of mlock with
> either calls to iio_claim_direct_mode (if it is an open coded
> version of what the mlock is intended for) or to introduce a
> lock within the driver itself with well defined scope covering
> whatever mlock was incorrectly being used for.
>
> Another traditional area for people first getting involved in IIO is
> to look at the drivers that are still in drivers/staging/iio
> but to be honest there are not many left there now so that isn't
> as fruitful as it used to be.  If you do want to look at those, do
> send a message to the list to confirm no one else is currently
> looking a the same driver.
Thanks for your suggestions.
I'd tried this staging driver cleanup long time back and I didn't find
much of the cleanup patches.
So, preferably I'll go ahead with the former suggestion on "removal of
mlock_mutex".
Meanwhile, I'll get started with testing this on a sensor as well.
I'll get back to you with any doubts while working on these.

Regards,
Karuna

Re: [GSoC] AD7292 driver project

[Himanshu Jha]

On Sat, Mar 16, 2019 at 04:09:36PM +0530, Karuna Grewal wrote:
> Hello,
> 
> I'm interested in working on the AD7292 driver for Linux kernel as a
> part of the GSoC project. I've previous experience working with device
> drivers and am also familiar with couple of Linux kernel's subsystems.
> For a starting point I wonder if someone can point out some tasks
> which I could work upon as the project page doesn't elaborate much
> about it.

Agreed!

You may try the following:
https://kernelnewbies.org/IIO_tasks

Please don't send these Tasks on iio list.

> In case the idea is to start working on the driver itself I'd like to
> discuss about the same.

My personal opinion: Try to get atleast a small patchset accepted in
the kernel. It helps you get familiar with all the tools and how kernel
cycle moves. I strongly agree with Jonathan on 'setup', whatever
hardware you plan to use in the project say., how would you build/test
kernel on Rpi or beagle or QEMU or diolan ? dt-overlay, acpi
enumeration ?

Pray that AD7292 doesn't have an unusual SPI interface.
Otherwise you end up like me ;)

If you really want to try some sensor, I would recommend https://www.tanotis.com/
to buy them as they have cheap and low duty-taxes+GST+ ...

In my case I ordered from mouser IIRC:
₹ 1,459.58(sensor) + ₹ 1,750.58(duty taxes + other taxes from Indian
Gov.)

Yeah, taxes are more than the actual sensor! Surreal :/

Feel free to query mentors and community with questions -- I would
join you too.


Goodluck!
-- 
Himanshu Jha
Undergraduate Student
Department of Electronics & Communication
Guru Tegh Bahadur Institute of Technology

Re: [GSoC] AD7292 driver project

[Alexandru Ardelean]

On Sun, Mar 17, 2019 at 7:19 PM Himanshu Jha
<himanshujha199640@gmail.com> wrote:
>
> On Sat, Mar 16, 2019 at 04:09:36PM +0530, Karuna Grewal wrote:
> > Hello,
> >
> > I'm interested in working on the AD7292 driver for Linux kernel as a
> > part of the GSoC project. I've previous experience working with device
> > drivers and am also familiar with couple of Linux kernel's subsystems.
> > For a starting point I wonder if someone can point out some tasks
> > which I could work upon as the project page doesn't elaborate much
> > about it.
>

Curios.
Is this project listed anywhere ?
If so, can we get a link ?

Thanks
Alex

> Agreed!
>
> You may try the following:
> https://kernelnewbies.org/IIO_tasks
>
> Please don't send these Tasks on iio list.
>
> > In case the idea is to start working on the driver itself I'd like to
> > discuss about the same.
>
> My personal opinion: Try to get atleast a small patchset accepted in
> the kernel. It helps you get familiar with all the tools and how kernel
> cycle moves. I strongly agree with Jonathan on 'setup', whatever
> hardware you plan to use in the project say., how would you build/test
> kernel on Rpi or beagle or QEMU or diolan ? dt-overlay, acpi
> enumeration ?
>
> Pray that AD7292 doesn't have an unusual SPI interface.
> Otherwise you end up like me ;)
>
> If you really want to try some sensor, I would recommend https://www.tanotis.com/
> to buy them as they have cheap and low duty-taxes+GST+ ...
>
> In my case I ordered from mouser IIRC:
> ₹ 1,459.58(sensor) + ₹ 1,750.58(duty taxes + other taxes from Indian
> Gov.)
>
> Yeah, taxes are more than the actual sensor! Surreal :/
>
> Feel free to query mentors and community with questions -- I would
> join you too.
>
>
> Goodluck!
> --
> Himanshu Jha
> Undergraduate Student
> Department of Electronics & Communication
> Guru Tegh Bahadur Institute of Technology

Re: [GSoC] AD7292 driver project

[Karuna Grewal]

On Mon, Mar 18, 2019 at 2:03 PM Alexandru Ardelean
<ardeleanalex@gmail.com> wrote:
>
> On Sun, Mar 17, 2019 at 7:19 PM Himanshu Jha
> <himanshujha199640@gmail.com> wrote:
> Curios.
> Is this project listed anywhere ?
> If so, can we get a link ?

Here's the link: https://wiki.linuxfoundation.org/gsoc/2019-gsoc-iio-driver

> > My personal opinion: Try to get atleast a small patchset accepted in
> > the kernel. It helps you get familiar with all the tools and how kernel
> > cycle moves. I strongly agree with Jonathan on 'setup', whatever
> > hardware you plan to use in the project say., how would you build/test
> > kernel on Rpi or beagle or QEMU or diolan ? dt-overlay, acpi
> > enumeration ?

I'll be using RPI w/ DT enumeration.