You might want to ask this question to the USB experts on the linux-usb ML - linux-usb@xxxxxxxxxxxxxxx HTH, -mandeep On Tue, Jul 1, 2014 at 10:10 PM, Raghavendra <arrao@xxxxxxx> wrote: > Hello, > > I have a query regarding DMA(Direct Memory Access) for the usb devices. > > The understanding of DMA actions over PCI is straight forward. PCI > devices support bus mastering capability, such that the PCI devices > could take the ownership of the bus and perform access to the memory > directly, and a software support exists for the same in Linux. > > As far as USB devices are concerned, they don’t have the bus mastering > capability like the PCI devices. > But the USB URB structure have a field named 'dma_addr_t transfer_dma', > used for DMA access. The USB driver allocate the DMA buffers coherently > and pass the DMA address to the URBs during its initialization. > As far as Linux is concerned, how the DMA action being taking place for > USB devices. As per my understanding, the USB host controller is taking > care of the DMA operations. But I require a little more insight into it. > > Further more, if it is possible for the USB devices, then can this > support be also extended towards low-end protocols such as I2C or SPI? > > Thanks, > Raghavendra > > ------------------------------------------------------------------------------------------------------------------------------- > [ C-DAC is on Social-Media too. Kindly follow us at: > Facebook: https://www.facebook.com/CDACINDIA & Twitter: @cdacindia ] > > This e-mail is for the sole use of the intended recipient(s) and may > contain confidential and privileged information. If you are not the > intended recipient, please contact the sender by reply e-mail and destroy > all copies and the original message. Any unauthorized review, use, > disclosure, dissemination, forwarding, printing or copying of this email > is strictly prohibited and appropriate legal action will be taken. > ------------------------------------------------------------------------------------------------------------------------------- > > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies@xxxxxxxxxxxxxxxxx > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
