From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Sailer Date: Wed, 17 Mar 1999 10:38:48 +0000 Subject: Re: Driver Writer's Questions Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-sound@vger.kernel.org Bob Miller wrote: > 1. (the big question) This device requires a single DMA buffer of up > to 8 Kb in main memory. It reads/writes the buffer circularly. It > can't chain buffers. Can I use the OSS DMA routines to set that > up somehow (how?), or do I have to write a non-OSS driver? If the device is not ISA, I wouldn't bother fitting it into the OSS framework, a stand alone driver (like I did for some PCI cards) is easier to do and more maitainable. > What does this imply for mmap? That the DMA buffer mappable is 8k max. The mmap interface is deprecated anyway. I've tried once to emulate the mmap interface on top of read/write, but it never worked well, if you don't want huge latencies. > 2. This device is capable of telling how many samples it has > read/written, with an accuracy of 1 sample. I'd like to export > that via the SNDCTL_DSP_GET{I,O}PTR, ioctls, but I can't see how > my driver can get control on those ioctls. Take a look at eg. the es1370 driver > 4. The mixer doesn't have a capability that corresponds to > SOUND_MIXER_VOLUME. If I don't implement SOUND_MIXER_VOLUME, will > I be incompatible with 99% of the apps? If I have to, I can fake Unlikely Tom