Re: [videobuf] Query: Condition bytesize limit in videobuf_reqbufs -> buf_setup() call?

[Mauro Carvalho Chehab <mchehab@redhat.com>]

Aguirre, Sergio wrote:
> Hi all,
> 
> While working on an old port of the omap3 camera-isp driver,
> I have faced some problem.
> 
> Basically, when calling VIDIOC_REQBUFS with a certain buffer
> Count, we had a software limit for total size, calculated depending on:
> 
>   Total bytesize = bytesperline x height x count
> 
> So, we had an arbitrary limit to, say 32 MB, which was generic.
> 
> Now, we want to condition it ONLY when MMAP buffers will be used.
> Meaning, we don't want to keep that policy when the kernel is not
> allocating the space
> 
> But the thing is that, according to videobuf documentation, buf_setup is
> the one who should put a RAM usage limit. BUT the memory type passed to
> reqbufs is not propagated to buf_setup, therefore forcing me to go to a
> non-standard memory limitation in my reqbufs callback function, instead
> of doing it properly inside buf_setup.
> 
> Is this scenario a good consideration to change buf_setup API, and
> propagate buffers memory type aswell?

I don't see any problem on propagating the memory type to buffer_setup, if
this is really needed. Yet, I can't see why you would restrict the buffer
size to 32 MB on one case, and not restrict the size at all with non-MMAP
types.

> I'll appreciate your inputs on this matter.
> 
> Regards,
> Sergio
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-- 

Cheers,
Mauro