Date: Wed, 24 Jan 1996 18:43:11 -0800 From: "Jordan K. Hubbard" <jkh@time.cdrom.com> To: Terry Lambert <terry@lambert.org> Cc: hasty@rah.star-gate.com (Amancio Hasty Jr.), james@miller.cs.uwm.edu, dufault@hda.com, hackers@FreeBSD.org, luigi@labinfo.iet.unipi.it, multimedia@rah.star-gate.com Subject: Re: Amancio's tv program with capture! Message-ID: <5959.822537791@time.cdrom.com> In-Reply-To: Your message of "Tue, 23 Jan 1996 16:52:11 MST." <199601232352.QAA18599@phaeton.artisoft.com>
next in thread | previous in thread | raw e-mail | index | archive | help
> I understand. You want to use theshared memory region as if it had > been created by an X server. Actually, it's not created by the server. It's created by whichever client wishes to use the Shm extension and the server is notified of the fact (and the ID). Jordan > > >From my understanding of the MIT shared memory extensions, this might > only be possible if you add some additional fields and values as if you > were an X server. > > My impression is that if the device memory mapped were from the memory > of a linear framebuffer, then it could be used for the data pointer > for the image without modification (you would have to fake a header for > it, but otherwise it should be treatable as a pixmap the size of the > memory area of a depth equal to the card settings, but without the > header. > > > I think the misconception here comes from expecting a device to have > the same memory layout in the mapped region as if it were on the user > side of the DDX interface already. I believe this would only be true > of specific devices, but not true in the general sense. > > > My inclination would be to tell you to avoid mapping it into the Xshm > interface unless you map it through an X server (which the Xshm currently > requires) that happens to use the mapping API in a (potentially) device > dependent fashion. > > Which is to say you must consider it as part of the DDX->frame buffer > interface, if you consider it at all. > > Without a lot of dancing to export a mapped region as a shared memory > segment (which is what I think you might really want instead), you are > going to have a hard time making the BSD (mmap) and SVR4 (shm) systems > talk nicely to each other, IMO. > > Terry Lambert > terry@lambert.org > --- > Any opinions in this posting are my own and not those of my present > or previous employers.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?5959.822537791>