Re: [PATCH 2/2] auxdisplay/ht16k33.c: Convert to use vm_map_pages_zero()

From: Miguel Ojeda
Date: Tue May 28 2019 - 15:07:17 EST

On Fri, May 24, 2019 at 8:07 AM Souptick Joarder <jrdr.linux@xxxxxxxxx> wrote:
> > > Taking a quick look now, by the way, why does vm_map_pages_zero() (and
> > > __vm_map_pages() etc.) get a pointer to an array instead of a pointer
> > > to the first element?
> For this particular driver, one page is getting mapped into vma. But
> there are other
> places where a entire page array ( with more than one pages) mapped into
> vma. That's the reason to pass pointer to an array and do rest of the operations
> inside __vm_map_pages().

Ah, "pointer to array of source kernel pages" made me think the actual
`struct page`s were the ones consecutive in memory, not the pointers.
Maybe "array of page pointers" is more clear.

> > Also, in __vm_map_pages(), semantically w.r.t. to the comment,
> > shouldn't the first check test for equality too? (i.e. for vm_pgoff ==
> > num)? (even if such case fails in the second test anyway).
> Sorry, didn't get it. Do you mean there should be a separate check for
> *vm_pgoff == num* ?

No, that the first check should be widened. I will send a patch.