On Tue, Aug 17, 2010 at 09:16:22AM +0100, Alan Cox wrote: > > We have a PCI based UART controller that is compatible with the > > existing 8250 serial driver in most aspects. However, one exception > > is that our UART controller can take advantage of the onboard DMA > > contoller to achieve higher throughput. Could you please share your > > insights about what is the proper way to add such DMA support into > > existing 8250 driver? > > I'd say the same as I said to the other folks who asked this - create a > new driver. All the DMA based 8250 devices have differing DMA engines > and it'll become unmanagable in the existing driver. > > Once we can see which bits of the existing code are useful for the DMA > 8250-style devices we can then create an 8250-lib.c which contains the > bits that are useful to 8250 and to non standard 8250-like devices. An existing example is drivers/serial/ioc3_serial.c. IOC3 is an SGI custom chip which is only being used in SGI systems. It has a PCI master and 486-style slave bus to which a SuperIO chip is connected. The IOC3 can either be configured to use the chip in legacy mode; then the standard 8250 driver will work fine. It also support a DMA mode with receive and transmit rings which make it similar to a network chip. Ralf -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
