On Friday 18 May 2012, Stephen Warren wrote: > > The driver can still request the dma line by name "tx" and the subsystem > > would pick one out of those with the same name. > > > > For the majority of cases, we would only need a single dma request line > > Hmm. Many devices have multiple different FIFOs, and hence multiple DMA > request signals (e.g. Tegra I2S has separate RX and TX FIFO, Tegra > S/PDIF has 2 FIFOs in each direction). That would require the driver to > always use get_by_name() to differentiate between 2/4 options for the > same DMA req or 2/4 different DMA requests. Most other bindings allow > use of get_by_id() or get_by_name() interchangeably. Ok, good point. So we could make the common case that they are numbered but not named and require all drivers to use named properties when there is the possibility that the device might be connected to multiple controllers, but that seems tricky because a driver can start being used on a platform that has only one controller and have no dma-name property in the device tree but then get used on a different soc that actually has multiple controllers. So if we do that, we might want to make the dma-names property mandatory for every device, and document what the names are. Another option would be to encode the direction in the property in a generic way and provide an API that lets you ask specifically for a read, write or readwrite channel out of the ones that are available, rather than assuming there is only one kind. Consequently, any device that uses more than one read channel or more than one write channel would still have to use names to identify them. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
