linux-kernel - Re: [PATCH 2.6.19-rc1 update4] drivers: add LCD support

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Message-ID: <653402b90610310558o40898827id1fe2ea0e1f28c2a@mail.gmail.com>
Date:	Tue, 31 Oct 2006 14:58:53 +0100
From:	"Miguel Ojeda" <maxextreme@...il.com>
To:	Franck <vagabon.xyz@...il.com>
Cc:	"Andrew Morton" <akpm@...l.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2.6.19-rc1 update4] drivers: add LCD support

On 10/31/06, Franck Bui-Huu <vagabon.xyz@...il.com> wrote:
> Miguel Ojeda wrote:
> > Again: Please read LDD3. It explains it well. Read all the "Remapping
> > RAM" chapter and you will understand what I've done, or just try to
> > remap RAM yourself with remap_pfn_range.
>
> Well, I'm trying to get an explanation here and here is what I get
> from you:
>
> MO  > LDD3 states it must work like this. (Note: it doesn't explain
>       why though)
> FBH > Weird I read the implementation of remap_pfn_range() and it
>       doesn't seem to have such restriction, I'm wondering how
>       things work...
> MO  > Again it's stated in LDD3, read again.
>
> Do you really think you explain anything with such replies ?
>

Do you really think I have to explain anything with my replies? I was
just trying to help you telling where I found the answer.

Anyway, isn't it explained in LDD3? isn't it stated in LDD3? I think
it is (yep, not deeply, but enough: other books cover that points
better and a device driver programmer doesn't have to know about
implementations, right?). Sure, neither the book or I didn't know
about the VM_PFNMAP change, but that doesn't change that I was trying
to encourage you to read such chapter, the same way I found the answer
there.

>
> Fortunately, Hugh Dickins gives a hint and it appears that the
> restriction doesn't hold anymore.
>
> > (I really tried it using
> > different ways and I couldn't map it with remap_pfn_range, it returns
> > you a place full with zeros, as LDD3 states).
>
> I'm really wondering how did you test the thing... ;)
>

And I still say I tried it, many ways, using remap_pfn_range() and
other weird things also. Finally, I thought something was wrong, so I
read LDD3 and I found the explanation about why my code mmap couldn't
mmap RAM. Also, my area was full of zeros, as LDD3 states. So I read a
little further and I did what "Remapping RAM" explains.

Anything else?

Bye,
       Miguel Ojeda
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