Could anybody help me here? Thanks Sing
-----Original Message----- From: Nallasellan, Singaravelan Sent: Friday, April 03, 2009 10:17 AM To: 'Arjan van de Ven' Cc: [email protected] Subject: RE: [Moblin Dev] msync usage on kernel buffers Arjan, Thanks for the response. Our driver has to reduce the time required to transfer the data as minimal as possible. We implemented mmap to reduce the overhead due to copy_from_user in kernel. How will the application communicate with the driver to inform the details buffer content such as the base address and the length? Is there a way to obtain the mmapped address from the user space buffer pointer passed in write? The amount of data to transfer is less than a MB. Could you please provide some info on "doorbell ioctl"? Is it a special ioctl or the ioctl to notify the driver with our own ioctl code? Thanks Sing -----Original Message----- From: Arjan van de Ven [mailto:[email protected]] Sent: Friday, April 03, 2009 10:05 AM To: Nallasellan, Singaravelan Cc: [email protected] Subject: Re: [Moblin Dev] msync usage on kernel buffers Nallasellan, Singaravelan wrote: > Hi, > > Our driver mmaps the kernel buffer and setup a DMA when the mmapped buffer is > filled with the data. > > How will the driver know whether the user space has filled the buffer with > the data? > > Can the application use msync to notify the driver with the starting address > and the size of the data as documented in msync? > > What is the file operation that the driver should implement for msync if it > is allowed? > if you don't have too much data to transport, I would actually recommend a write() not mmap() method. if you have really high volumes of data (gigabyte per second or so) then you might need to implement a doorbell ioctl or so. _______________________________________________ Moblin dev Mailing List [email protected] To manage or unsubscribe from this mailing list visit: https://lists.moblin.org/mailman/listinfo/dev or your user account on http://moblin.org once logged in. For more information on the Moblin Developer Mailing lists visit: http://moblin.org/community/mailing-lists
