A: http://en.wikipedia.org/wiki/Top_post
Q: Were do I find info about this thing called top-posting?
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?

A: No.
Q: Should I include quotations after my reply?

http://daringfireball.net/2007/07/on_top

On Thu, Feb 11, 2021 at 08:38:40AM +0000, Noam Liron wrote:

Hi Greg,

I am writing you again on the below subject, as I would like to get a
"high level" opinion, and you are probably the most experienced ...

I am not a DMA expert at all, why not ask the dma developers instead?

As I wrote below, I cannot rely on the DMA mask, as some USB
allocation are not affected by it.

Why "some" and not "others"?  Perhaps you need to fix your platform code
to prevent that from happening instead?  Why is USB unique here?

I thought of using private DMA pool that will be allocated where I
need it (at the start of physical memory). However, this means adding
specific ASIC code, which is less elegant.
Do you think that's the right way?

I do not know your platform, only you do.

But I do think you should not be doing new development on 4.14, as that
is a very old and obsolete kernel and the dma code in the kernel has
changed a lot since 2017.

good luck!

greg k-h