rtems-examples hello no output devfs

[Sebastian Huber]

On 14/02/2020 16:29, Joel Sherrill wrote:

>
>
> On Fri, Feb 14, 2020 at 9:16 AM Sebastian Huber 
> <sebastian.huber at embedded-brains.de 
> <mailto:sebastian.huber at embedded-brains.de>> wrote:
>
>     On 14/02/2020 15:45, Joel Sherrill wrote:
>
>>     On Fri, Feb 14, 2020 at 7:08 AM Sebastian Huber
>>     <sebastian.huber at embedded-brains.de
>>     <mailto:sebastian.huber at embedded-brains.de>> wrote:
>>
>>         On 14/02/2020 13:57, Joel Sherrill wrote:
>>
>>         > Hi
>>         >
>>         > I haven't investigated or checked on other bsps but the
>>         xilinx qemu
>>         > bsp has no output with the hello world in examples. It uses
>>         the devfs.
>>         > Changing it to the default filesystem results in it working.
>>         >
>>         > I am suspicious of something with all the termios and new
>>         console
>>         > changes breaking it.
>>         The devfs works only with legacy IO drivers. The Termios
>>         drivers depend
>>         on IMFS. I would like to remove the devfs in the future. The
>>         IMFS is
>>         highly configurable, there is no need for an additional
>>         in-memory file
>>         system.
>>
>>
>>     Do not remove it. Please fix it.
>
>     The IMFS should be improved, so that we can remove the devfs. We
>     already have a bunch of configuration options to customize it:
>
>     https://docs.rtems.org/branches/master/c-user/configuring_a_system.html#file-system-configuration-parameters
>
>
> You should look at the requirements for the older ESA RTEMS versions. 
> They
> had very specific requirements which ended up with the filesystem code
> largerly removed AFAIK.

You can get rid of the file system with the 
CONFIGURE_APPLICATION_DISABLE_FILESYSTEM configuration option.

>
> And you did break existing code in the public repository. If we need 
> more tests
> to ensure it works, then so be it. It is a feature in the current code 
> base and it
> just broke.
>
> Until the IMFS can be proved to be configurable to meet the 
> requirements that
> resulted in the filesystem code being removed/minimized in the old 
> ESA  versions
> and other folks who needed the simplest possible infrastructure for 
> devices so
> our normal frameworks would work, it needs to stay and work.
If you want a minimal setup, then why do you want to use the POSIX 
open/read/write API to access devices? The POSIX functions pull in errno 
for example which pulls in the re-entrancy support which pulls in a hell 
of dependencies. Why do you want to use a console driver with Termios in 
a minimal setup?
>
> You can have a goal which you may or may nor achieve but you can't 
> leave a
> trail of code that is broken just because you don't like it.
To fix this break, I suggest to map CONFIGURE_FILESYSTEM_DEVFS to a 
suitable IMFS configuration similar to 
CONFIGURE_USE_MINIIMFS_AS_BASE_FILESYSTEM.
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