the cost of EXPORT_SYMBOL_GPL

[Greg KH]

On Wed, Jun 17, 2020 at 09:58:03AM +0200, Tomek The Messenger wrote:
> Hi
> Thanks for reply.
> We make some proxy layer in linux /sys. So for example we have directories:
> /sys/resets
> /sys/routers

Really?  That's a total abuse of sysfs, don't do that.

Seriously, that's not ok at all.

> etc.
> So if user wants to get to know what is the reset reason he doesn't use
> devmem 0xfff...., he just read the file in /sys/resets/..
> If user wants to know some routing path he doesn't read registers via
> devmem, he only reads some file in /sys/routers which gives him output.
> So this is in order to facilitate reading/writing to registers. Instead of
> searching in documentation concrete registers users have some helper proxy
> layer in sysfs. And for each directory in /sys there is separate kernel
> module. Division is based on some functionalities like resets, routing etc.
> And the problem is should this 6th kernel module perform role of getting
> access to all registers or only to parts which are used by more than one
> kernel module? Now I am using second approach but when I am looking at the
> code it looks terrible. For example #define for register X and function to
> access it, is in module A, for egister Y in module B, for register Z in 6th
> kernel module. There is mess I think and maybe better approach is to put
> all API to 6th kernel module?

I really do not understand at all, sorry.  Why are you using sysfs for
something that it is not designed for?  And sysfs directory structure
has nothing to do with kernel module names/structures.

Do you have a pointer to your code somewhere so that we can review it
and suggest the correct apis you should be using instead?

thanks,

greg k-h