Thanks Takashi. Then what would be the best way to know when the mmaped buffer has been filled. So that I can take action to send it to the hardware?
Should I use the runtime->control->appl_ptr or runtime->status->appl_ptr to get the position the app has filled?
-----Original Message----- From: Takashi Iwai [mailto:tiwai@suse.de] Sent: Tuesday, February 24, 2009 12:55 AM To: Harsha, Priya Cc: alsa-devel@alsa-project.org Subject: Re: clarification on mmap
At Mon, 23 Feb 2009 22:21:24 +0530, Harsha, Priya wrote:
Thank you. Can I use .ack callback to know that the mmaped buffer has been filled by the user?
Not really. It's just for explicit read/write modes.
How would I know how much the user has written into the buffer that time?
You can check appl_ptr at any time. This corresponds to the position the app has filled.
Takashi
Would I need to have the pointers calculated and tracked myself or is there a field in the structures that I can read and find out?
-----Original Message----- From: Takashi Iwai [mailto:tiwai@suse.de] Sent: Monday, February 23, 2009 8:57 PM To: Harsha, Priya Cc: alsa-devel@alsa-project.org Subject: Re: clarification on mmap
At Mon, 23 Feb 2009 18:59:11 +0530, Harsha, Priya wrote:
Hi,
I have a question on mmap. If I give my .info to be _MMAP and _MMAP_VALID. Will ALSA framework internally take care of mmap-ing the kernel buffer that has been pre-allocated in the .probe call? Do I need to do anything special to mmap a kernel buffer into user space? Just accessing the runtime->dma_area would allow me to access user data right?
Yes. The buffers allocated via preallocator are supposed to be mmappable, so you can simply pass _MMAP* flag there.
Takashi