linux-kernel - Re: [PATCH 4/4] ALSA: add dummy function to support shared mmap in nommu Blackfin arch

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Message-ID: <386072610809020259hd61d8barec55e453579ade1a@mail.gmail.com>
Date:	Tue, 2 Sep 2008 17:59:40 +0800
From:	"Bryan Wu" <cooloney@...nel.org>
To:	"Takashi Iwai" <tiwai@...e.de>
Cc:	"Cai, Cliff" <Cliff.Cai@...log.com>, perex@...ex.cz,
	liam.girdwood@...fsonmicro.com,
	broonie@...nsource.wolfsonmicro.com, alsa-devel@...a-project.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] ALSA: add dummy function to support shared mmap in nommu Blackfin arch

On Tue, Sep 2, 2008 at 5:41 PM, Takashi Iwai <tiwai@...e.de> wrote:
> At Tue, 2 Sep 2008 11:16:37 +0800,
> Cai, Cliff wrote:
>>
>>
>> > @@ -3419,5 +3426,6 @@ const struct file_operations snd_pcm_f_ops[2] =
>> {
>> >             .compat_ioctl =         snd_pcm_ioctl_compat,
>> >             .mmap =                 snd_pcm_mmap,
>> >             .fasync =               snd_pcm_fasync,
>> > +           .get_unmapped_area =    dummy_get_unmapped_area,
>> >     }
>> >  };
>>
>> >I don't think adding this dummy get_unmapped_area unconditionally for
>> every driver is good.  This overrides the default
>> >mm->get_unmaped_area.
>> But without this dummy function,shared mmap on nommu arch would
>> fail,refer to validate_mmap_request() in mm/nommu.c.
>
> Yes, I know it's needed for nommu.  That's why I wrote
> "unconditionally" in the above.
>
>> May be we can add a kernel config item to include or not include this
>> function depending on non-mmu or mmu arch.
>
> Checking CONFIG_MMU may suffice?
>

Right, I post a v2 patch including this checking.

Thanks
-Bryan
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