> -----Original Message----- > From: Mauro Carvalho Chehab [mailto:mche...@redhat.com] > Sent: Wednesday, May 05, 2010 6:24 PM > To: Aguirre, Sergio > Cc: linux-media@vger.kernel.org > Subject: Re: [videobuf] Query: Condition bytesize limit in > videobuf_reqbufs -> buf_setup() call? > > 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.
Ok, my reason for doing that is because I thought that there should be a memory limit in whichever place you're doing the buffer allocations. MMAP is allocating buffers in kernel, so kernel should provide a memory restriction, if applies. USERPTR is allocating buffers in userspace, so userspace should provide a memory restriction, if applies. Please correct me if my reasoning is not correct. Regards, Sergio > > > I'll appreciate your inputs on this matter. > > > > Regards, > > Sergio > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-media" > in > > the body of a message to majord...@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > -- > > Cheers, > Mauro -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
