AW: Re: Some thoughts about the flash device driver and the flashdisk block driver

[Joel Sherrill]

Astrid Hanssen wrote:
> Hi Chris,
>
>   
>>> I am happy to find there was a new concept invented recently, the
>>> libchip/flash device driver(s) and a flashdisk block driver.
>>> Because I believe this to be a very nice thing and opens the door
>>> to many new applications, I immediately decided to integrate this
>>> to the BSP I am working on.
>>>       
>> Excellent. I have it here on a mcf5235 board and it is working well.
>>     
>
> This is very fine as I used your mcf5235 implementation as a basis for
> the mcf5208 :-)
>
>   
>> [shell, mounting, and scripting]
>>     
>
> This looks nice. Is there any documentation about this yet?
> I did not find enough info for feeling able to play with it.
>
>   
Yep.  Not enough documentation yet.  A couple of good
sample tests though.  Try fileio and telnetd from the
network demos. 

And there is always the source code. :-D
>>> After the flash driver will be thoroughly tested, I feel like
>>> submitting it to libchip/flash.
>>>       
>> Please do. The more drivers the better. :-)
>>     
>
> Yes, and the mcf5208 BSP also.
> But for the BSP I will probably need some help with committing.
> I will have to ask Joel about this when time has come.
>
>   
I'm here.  Let's just make sure it has proper licensing,
avoids duplicating code it can share, and works against
the CVS head. 

At this point, it wouldn't be premature to add it to the
Wiki and start to make sure it is documented well
enough where someone else can configure the board
correctly, download and run an application.

If you do that, merging it will be a breeze.
> you very much, this makes the idea more clear to me.
> I will try it out.
>
> I am still not sure whether it is recommended to include
> these parts into bspstart.c, or whether they should reside
> in the application. In the first thought, they belong to
> the BSP because the hardware is well defined, and therefore
> this driver can also be.
>
>   
Please do NOT put this in bspstart.c.  I can't emphasize
that enough. 

bspstart.c is in EVERY application and flash disk
support isn't part of EVERY application.  Moreover,
your 5208 BSP could grow to support BSP variants
which are similar to but not exactly like the board
you are using.
> And why isn't rtems_flashdisk_io_ops contained in flashdisk.c?
> I do not see any application or BSP dependencies.
>
> Sorry for my newbie questions, just trying to understand RTEMS
> and its concepts better.
>
>   
I should probably clean this list up and formalize it but here
goes:


+ Many small pieces tied together to produce a nice whole.

+ Make the BSP have the smallest pieces possible.

+ Make sure your small pieces don't have unnecessary
   dependencies.

+ Make pieces shareable across as many CPUs/BSPs as
    possible.

We really want end users to be able to

(1) very easily use BSPs for commercially available boards

(2) easily craft custom BSPs without  inventing everything.


--joel

> Regards,
> Astrid
>
>
>
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