Re: Are media drivers abusing of GFP_DMA? - was: Re: [LSF/MM TOPIC NOTES] x86 ZONE_DMA love

From: Laurent Pinchart
Date: Mon May 07 2018 - 09:26:05 EST


Hi Mauro,

On Saturday, 5 May 2018 19:08:15 EEST Mauro Carvalho Chehab wrote:
> There was a recent discussion about the use/abuse of GFP_DMA flag when
> allocating memories at LSF/MM 2018 (see Luis notes enclosed).
>
> The idea seems to be to remove it, using CMA instead. Before doing that,
> better to check if what we have on media is are valid use cases for it, or
> if it is there just due to some misunderstanding (or because it was
> copied from some other code).
>
> Hans de Goede sent us today a patch stopping abuse at gspca, and I'm
> also posting today two other patches meant to stop abuse of it on USB
> drivers. Still, there are 4 platform drivers using it:
>
> $ git grep -l -E "GFP_DMA\\b" drivers/media/
> drivers/media/platform/omap3isp/ispstat.c
> drivers/media/platform/sti/bdisp/bdisp-hw.c
> drivers/media/platform/sti/hva/hva-mem.c
> drivers/media/spi/cxd2880-spi.c
>
> Could you please check if GFP_DMA is really needed there, or if it is
> just because of some cut-and-paste from some other place?

I started looking at that for the omap3isp driver but Sakari beat me at
submitting a patch. GFP_DMA isn't needed for omap3isp.

--
Regards,

Laurent Pinchart