[PATCH 0/1][SRU][F] Dynamically set AD5593R channel modes

[Stefan Bader]

On 15.09.20 07:08, AceLan Kao wrote:
> BugLink: https://bugs.launchpad.net/bugs/1895612
> 
> [Impact]
> On Advantech UNO-420 development platform, we need a generic way to set
> the pin mode.
> Upstream would like us to leverage ACPI override method to change the
> modes, but in Ubuntu core, we can't generate a new initramfs and boot up
> with the generated initramfs.
> 
> [Fix]
> Add a module parameter to assign pin modes while loading ad5593r driver.
> 
> [Test]
> Verified on Advantech UNO-420 platform.
> 
> [Regression Potential]
> Low, it checks the length of the passed parameter, and checks every bytes
> in it to make sure it's a valid argument.
> 
> William Sung (1):
>   iio: dac: ad5593r: Dynamically set AD5593R channel modes
> 
>  drivers/iio/dac/ad5592r-base.c | 21 +++++++++++++---
>  drivers/iio/dac/ad5592r-base.h |  4 ++++
>  drivers/iio/dac/ad5593r.c      | 44 ++++++++++++++++++++++++++++++++++
>  3 files changed, 66 insertions(+), 3 deletions(-)
> 

I did discuss this with Andy today. Technically I guess this is ok if we are
sure that you cannot damage the HW or leverage the interface for attacks by
passing either random or certain sequences of numbers. The allowed values seem
to be checked, so the question only is what one could do with random
alternations of those.

The other thing we want to avoid is to have a module argument name either clash
with a possible upstream name or be taken as something that will be carried
onward into later series.

So question: could we prefix the paramenter with ubuntu, so it would become
ubuntu_ch_mode=... Then maybe we could add Documentation/admin-guide/
ubuntu-kernel-parameters.txt which explains the usage and also clarifies that
this is an experimental option which may or (rather) may not be present in newer
kernels.

-Stefan

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