Hi,

quoted

Then, I added the example code in the documentation using EADDRNOTAVAIL.
Yes, I was brave with this one. Yet, EINVAL, EBUSY, ENOENT, did not
really cut it and are so heavily used in drivers that they turned into a
generic "something is wrong" error. I tried here to use a not overloaded
error code in order to be specific again. Since the patches were
accepted, I assumed it wasn't seen as a namespace violation. (Then
again, it probably would have been if that error code would go out to
userspace) Naturally, I didn't have the resources to check all patches
for a consistent error code.

The problem with the current approach is that people (me included) keep
telling people to use this or that error code in an attempt to achieve
some kind of consistency. Also using an error message to distinguish
between reasons for failure makes it impossible to handle the error
other than by visual inspection. Granted, there are currently no code
paths that require this.

Yes, so currently, this is rather a cosmetic change. And for that, it is
quite intrusive. I think something like this is needed somewhen as part
of a bigger overhaul. That's what I called "master plan" last time. That
could be that resource handling gets aligned in general, also taking
e.g. interrupt resources into account. But only changing error code
handling for this function, doesn't seem too useful to me and might even
need another change later, then.

One problem with the original patch was also that it didn't actually
convert any existing uses, so there was little chance of anyone noticing

Like with the error codes now, there are so many different ways of
handling resources that I did not want to mass convert all the drivers
without being able to test them. I was hoping for a migration over time
with patches from people who really tested what they did.

potential problems. More than a year later this function is used by many
subsystems and a lot of drivers. It just so happened that I observed how
many people just didn't know what error codes to choose and often just
grabbing one randomly.

Yes, and concerning resources this needs cleaning on a bigger scale IMO.

By adding devm_ioremap_resource() and having it return ERR_PTR()-encoded
error codes we get rid of all these problems and put the responsibility
for choosing the error code where, in my opinion, it belongs: the
failing function.

For completeness, it leaves the problem that people might forget to use
ERR_PTR (seen that often in the clk framework). And the change is huge
while I can't see any real benefit right now.

quoted

When working with this function, there was also the idea to abstract
getting the resource away. Which then gave Sascha Hauer and me the
question, if drivers really have to do this or if this couldn't be done
by the kernel somehow, i.e. giving the drivers already the resources
they need, completely prepared.

I'm not sure I like that very much. That could possibly lead to a new
problem where drivers that need to do something special have to jump
through hoops to achieve something that may otherwise be simple.

I assume that drivers are already doing something special :) So, that
would turn up in the conversion process. I can't promise that it would
really work, it would need some playing around.

Anyway, if people don't think this is a sensible conversion I should
waste no more time on it. On the other hand I have the patch series
ready so I might as well post it for broader review.

Working on patches is hardly a waste. Even if not accepted, you gain
understanding. Please put me on CC, if you post the patches.

Regards,

   Wolfram

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