linux-kernel - Re: [PATCH 4/8] fbdev: ssd1307fb: Use vmalloc to allocate video memory.

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Message-ID: <CAMuHMdXTinYuQTpQGc6WyVNpCOhAHPrkHKfRRQAM3Wy6Cg4wvQ@mail.gmail.com>
Date:	Sat, 14 Mar 2015 23:02:43 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Thomas Niederprüm <niederp@...sik.uni-kl.de>
Cc:	Tomi Valkeinen <tomi.valkeinen@...com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/8] fbdev: ssd1307fb: Use vmalloc to allocate video memory.

On Fri, Mar 13, 2015 at 10:31 PM, Thomas Niederprüm
<niederp@...sik.uni-kl.de> wrote:
> Am Tue, 10 Mar 2015 13:28:25 +0200
> schrieb Tomi Valkeinen <tomi.valkeinen@...com>:
>> Also, isn't doing __pa() for the memory returned by vmalloc plain
>> wrong?
>
>> What was the crash about when using kmalloc? It would be good to fix
>> defio, as I don't see why it should not work with kmalloced memory.
>
> The main challenge here is that the memory handed to userspace upon
> mmap call needs to be page aligned. The memory returned by kmalloc has
> no such alignment, but the pointer presented to the userspace program
> gets aligned to next page boundary. It's not clear to me whether there
> is an easy way to obtain page aligned kmalloc memory. Memory
> allocated by vmalloc on the other hand is always aligned to page
> boundaries. This is why I chose to go for vmalloc.

__get_free_pages()?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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