linux-kernel - Re: [PATCH 2/2] auxdisplay/ht16k33.c: Convert to use vm_map_pages

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Message-ID: <CAFqt6zaUhPJYozmq-m_BjJTh5EUmsQoE4yZ+Ovv6F-ymns+JGA@mail.gmail.com>
Date:   Fri, 24 May 2019 11:37:12 +0530
From:   Souptick Joarder <jrdr.linux@...il.com>
To:     Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
Cc:     Robin van der Gracht <robin@...tonic.nl>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH 2/2] auxdisplay/ht16k33.c: Convert to use vm_map_pages_zero()

On Fri, May 24, 2019 at 9:52 AM Miguel Ojeda
<miguel.ojeda.sandonis@...il.com> wrote:
>
> On Thu, May 23, 2019 at 2:58 PM Miguel Ojeda
> <miguel.ojeda.sandonis@...il.com> 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().

https://lkml.org/lkml/2019/3/18/1265

>
> 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* ?


> Cheers,
> Miguel